JFK Assassination Forum
JFK Assassination Discussion & Debate => JFK Assassination Discussion & Debate => Topic started by: Joe Elliott on May 17, 2023, 12:58:30 PM
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Would A Bullet Really Knock You Backwards? DEBUNKED
At around the 2:56 mark, the narrator states:
"only results in a backwards motion of 80 kg target body of 0.01-0.18 m/s,"
Or, to units readers may be more familiar with:
"only results in a backwards motion of 176 pound target body of 0.02-0.40 mph,"
President Kennedy's head backwards motion, at it's maximum speed, at frame z318, was 1.9 mph. Much faster than one would expect from any plausible weapon. But well within the capabilities of JFK's own muscles, if the bullet triggered a Neurological Spasm, which is immoral to demonstrate with humans but can and has been shown in films of animals, like that of the goat in the 1947 U. S. Army tests.
Of course, a more powerful weapon, like an anti-tank gun (equipped with a silencer, do doubt :) ), could, in theory push JFK's head backwards at that speed. But there are multiple problems, even with that:
1. Most fundamentally, a push from a bullet or a shell would give an almost instant impulse to JFK's head, pushing JFK's head with constant momentum. Resulting in an initial fast speed (that momentum being used to push the head alone) followed by a slower speed (the same momentum pushing both the head and torso). Instead, what is measured in the Zapruder film by Physics graduate student William Hoffman, is a slow initial speed backwards, that gradually builds up, 4 frames later, to 1.9 mph.
2. As pointed out, a weapon that powerful would splatter the whole head, not just part if it, in many directions. There would be no head left afterwards.
3. Also, a bullet, or a shell, would only pass on some of it's momentum, not all of it, as the projectile would pass through the head and continue with most of it's momentum.
But, with most people not understanding simple Classical Physics, the "Back and to the Left" argument should still continue to hold great sway over the masses.
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Yes, they do. I used to have a video clip of a guy who accidentally got shot from the front with a rifle. He was just walking and clapping when his friend's gun went off. The gun was positioned in front of and slightly to the side of him. As soon as the bullet hit, his head was thrown backward and he collapsed onto the ground. So yes, it does happen.
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Yes, they do. I used to have a video clip of a guy who accidentally got shot from the front with a rifle. He was just walking and clapping when his friend's gun went off. The gun was positioned in front of and slightly to the side of him. As soon as the bullet hit, his head was thrown backward and he collapsed onto the ground. So yes, it does happen.
What was the type of the rifle?
What was the type of the bullet?
Most importantly, what was the mass and the velocity of the bullet?
At what speed did the victim's head move backwards?
In other words, is there an anomaly here? Does the head move backwards with more momentum than the bullet?
If not, there is nothing to explain. Once again, we would have proven that the laws of physics hold. That people are not flung away from bullets with more momentum than a bullet carries.
If there is an anomaly here, one would need to look into other possibilities. JFK was not instantly killed by the bullet that struck him in the head. He still had weak breathing and a weak heartbeat for up to 20 minutes after being shot. Martin Luther King was not instantly killed by the bullet that struck him in the head.
Is it possible the victim in this case was not killed instantly?
If so, is it possible that it was it was the victim's own muscles that propelled him backwards? There is a flash of light, There is a loud sound. A person who is not killed outright, or even totally missed, might instinctively jerk their head backwards away from the rifle. And with more momentum than that carried by the rifle bullet.
And, it is also possible that the rifle bullet went directly through the brain, which, just like JFK, could cause his head and torso to be flung back with more momentum than a bullet, due to a bullet generated neurological spasm. Regardless of whether he was shot from the front, or behind, we would see the stronger muscles of his body move the head and torso backwards, if a neurological spasm occurred.
We need to more information before we conclude that:
1. Rifles cause a victim to move backwards with more momentum than the bullet carries. Seemingly being a special exception to Newton's Laws of Motion.
or:
2. There are weapons out there where the projectile carries enough momentum to push and torso back at 1.9 mph, as seen in the Zapruder film, without totally blowing off the head.
You have not provided that information. Instead, you only bring a story.
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What was the type of the rifle?
What was the type of the bullet?
Most importantly, what was the mass and the velocity of the bullet?
At what speed did the victim's head move backwards?
In other words, is there an anomaly here? Does the head move backwards with more momentum than the bullet?
If not, there is nothing to explain. Once again, we would have proven that the laws of physics hold. That people are not flung away from bullets with more momentum than a bullet carries.
It depends also on whether the bullet exited and, if so, at what speed.
In the case of 6.5 mm 10 g (.01kg) jacketed bullet at 2000 fps (610 m/s) the maximum momentum transfer is p=.01x610=6.1 kg m/sec. For a 61 kg person on a frictionless surface, absorbing the entire bullet momentum (no bullet exit), the person would move .1m/s or 10 cm/sec, which is not much really. If it hit the head, the head would move much more rapidly. A 6.1 kg head would move 1 m/s or 5 cm (2 in.) in 1/20th of a second. One sees this kind of movement in the z film between frames 312 and 313.
If the bullet energy causes matter to explode from the exit wound due to pressure build-up in the body/head, the momentum of the ejected matter could easily exceed the forward momentum imparted by the bullet. In that case the body/head would recoil in the opposite direction to the ejected matter. That is consistent with what is seen in the zfilm as the head recoils immediately after z313 and the body follows.
And, it is also possible that the rifle bullet went directly through the brain, which, just like JFK, could cause his head and torso to be flung back with more momentum than a bullet, due to a bullet generated neurological spasm. Regardless of whether he was shot from the front, or behind, we would see the stronger muscles of his body move the head and torso backwards, if a neurological spasm occurred.
I don't think this has ever been documented as a real thing. There are many films of people being shot in the back of the head and they just fall over unconscious if not dead.
1. Rifles cause a victim to move backwards with more momentum than the bullet carries. Seemingly being a special exception to Newton's Laws of Motion.
There is, of course, no exception to the law of Conservation of Momentum which goes beyond Newton and applies to all of physics since Newton (eg Electromagnetism, Relativity and Quantum Mechanics). Conservation of momentum was, for example, how the neutron and neutrinos were discovered.
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Would A Bullet Really Knock You Backwards? DEBUNKED
The video posted in the OP has no bearing on JFK's head-shot.
JFK's head explodes as a result of the shot. Pieces of his skull are blown in various directions. Jets of material, possibly brain matter and skull, are seen emanating from the top of his head. The top of his head literally blows off as a result of the shot.
To imagine there is no significant transfer of momentum from the bullet to the head in this instance is ludicrous.
The force required to achieve this incredible amount of damage would surely be reflected in how JFK's head moves as a result of this impact.
Neurological spasm and the jet effect are unnecessary contrivances when coming to explain the "back and to the left" movement of JFK as a result of the head-shot.
Good, old-fashioned physics is more than sufficient.
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Neurological spasm and the jet effect are unnecessary contrivances when coming to explain the "back and to the left" movement of JFK as a result of the head-shot.
Good, old-fashioned physics is more than sufficient.
?? How is "jet-effect" not "good old-fashioned physics"? It is just conservation of momentum. Alvarez did not go beyond Newton's laws in explaining it.
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It depends also on whether the bullet exited and, if so, at what speed.
Correct.
In the case of 6.5 mm 10 g (.01kg) jacketed bullet at 2000 fps (610 m/s) the maximum momentum transfer is p=.01x610=6.1 kg m/sec. For a 61 kg person on a frictionless surface, absorbing the entire bullet momentum (no bullet exit), the person would move .1m/s or 10 cm/sec, which is not much really. If it hit the head, the head would move much more rapidly. A 6.1 kg head would move 1 m/s or 5 cm (2 in.) in 1/20th of a second. One sees this kind of movement in the z film between frames 312 and 313.
Correct. The initial movement, during the z312-z313 interval, is consistent with a WCC/MC bullet striking from behind.
If the bullet energy causes matter to explode from the exit wound due to pressure build-up in the body/head, the momentum of the ejected matter could easily exceed the forward momentum imparted by the bullet. In that case the body/head would recoil in the opposite direction to the ejected matter. That is consistent with what is seen in the zfilm as the head recoils immediately after z313 and the body follows.
Yes and no. In theory, the "Jet Effect" could cause a 'target' to move back toward the rifle. This has been demonstrated with various targets like taped melons.
But this did not happen in the JFK murder. Because the head initially moved forward. If the "Jet Effect" occurred, JFK's head would have started moving backwards almost immediately, within 5 to 10 milliseconds of the bullet impact, because there would be no big 55 millisecond delay in the head being struck and organic material starting to move forward. We can see in frame z313 that the organic material had already started moving, right about the time the shutter closed on z312. A piece of bone, likely the 'Harper fragment', is already two to four feet away from the head in z313.
Note: The 'Harper fragment' is two to four feet from the head because z313 does not show an instant of time. When the shutter opened for z313, the fragment was two feet away. When it closed, it was four feet away.
The "Jet Effect" can occur. But in all cases, it is immediate. A taped melon doesn't move two inches away from the shooter, and then reverse directions, like seen with JFK.
I would be happy to change my mind, if someone can site a case where a 'target', like a taped melon, did reverse direction of movement due to the "Jet Effect".
I don't think this has ever been documented as a real thing. There are many films of people being shot in the back of the head and they just fall over unconscious if not dead.
As far as I know, this never occurs in animals with subsonic handgun bullets. Only with supersonic (generally rifle) bullets.
Not going to documented in humans, because a rifle bullet strike, causing a human head to explode like the case of JFK, is too gory, too much an insult to human dignity, to be shown. This is a very strong taboo against this. CTers broke the taboo in the JFK case, but showing a film of someone else's head exploding could get you sued by their family. The only test that can be run is on animals.
There is, of course, no exception to the law of Conservation of Momentum which goes beyond Newton and applies to all of physics since Newton (eg Electromagnetism, Relativity and Quantum Mechanics). Conservation of momentum was, for example, how the neutron and neutrinos were discovered.
Agreed. But some CTers seemed to think a 'theory' they present does not need to be explained by classical physics. There is no need for them to explain how a bullet striking from the front could cause JFK's head to initial move forward, then start to move the head backwards, gradually increasing momentum from z313 through z318, reaching the maximum speed at z318. They seem to feel that classical physics can be ignored.
The only theory that explains this movement is the 'Neurological Spasm' theory.
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Neurological spasm and the jet effect are unnecessary contrivances when coming to explain the "back and to the left" movement of JFK as a result of the head-shot.
Good, old-fashioned physics is more than sufficient.
Well, good, I finally have someone to talk over 'old-fashioned physics' with.
How to you explain the motion of JFK's head, during z312-z318. This motion is detailed in Josiah Thompson's book "Six Seconds in Dallas", not by Josiah Thompson but by Physics graduate student William Hoffman. In Hoffman's data:
from z312-z313: The head moves forward at 2 mph.
from z313-z318: The head starts to move backwards, gradually moving faster and faster, reaching a maximum speed of 1.9 mph at z318.
How does a frontal shot explain this?
Why would it cause an initial movement of the head forward?
And when the backward movement starts, why does the speed gradually accelerated? Why wouldn't the bullet passing through the head transfer all it's momentum with 1 to 2 milliseconds, but instead transfer it's momentum over the course of 200 milliseconds?
By the way, the acceleration of the limousine does not explain this. William Hoffman, back in 1966, was way ahead of everyone. He also plotted the speed of the limousine and the acceleration of the limousine is not even a tenth of the amount of accelerated needed to explain the backwards movement of JFK's head.
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Also, it is not proper science, when looking into a problem to declare some theories are 'unnecessary contrivances' and should not be considered. "The theory of Continental Drift is an unnecessary contrivance, and must not be considered a possible explanation for why an animal specie from the distance past appears to have been on both sides of the Atlantic, now separated by thousands of miles".
And so it is not proper science, when looking into a problem to declare:
1. A shot from the front, is an unnecessary contrivance to explain the movement of JFK's head.
2. The 'Jet Effect', is an unnecessary contrivance to explain the movement of JFK's head.
3. The 'Neurological Spam', is an unnecessary contrivance to explain the movement of JFK's head.
All three theories must be considered. And since only the "Neurological Spam' theory explains the movement of JFK's head, it is the theory that should be accepted as the one most probably true. Unless future data collected requires a reassessment". Like video of a taped melon reversing direction. Or video of a bullet striking a target and causing the target to gradually accelerate over the course of 200 milliseconds, or a fifth of a second. But until such a time, the "Neurological Spam' theory is the one I am going to go with.
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Correct.
Correct. The initial movement, during the z312-z313 interval, is consistent with a WCC/MC bullet striking from behind.
Yes and no. In theory, the "Jet Effect" could cause a 'target' to move back toward the rifle. This has been demonstrated with various targets like taped melons.
But this did not happen in the JFK murder. Because the head initially moved forward. If the "Jet Effect" occurred, JFK's head would have started moving backwards almost immediately, within 5 to 10 milliseconds of the bullet impact, because there would be no big 55 millisecond delay in the head being struck and organic material starting to move forward. We can see in frame z313 that the organic material had already started moving, right about the time the shutter closed on z312. A piece of bone, likely the 'Harper fragment', is already two to four feet away from the head in z313.
The forward bullet momentum is imparted to the head before the head explodes so the head is driven forward before it is driven backward. One has to take into account that the rearward momentum imparted by the exploding matter from the head first had to stop the head from going forward. It is already accelerating rearward in z313.
The "Jet Effect" can occur. But in all cases, it is immediate. A taped melon doesn't move two inches away from the shooter, and then reverse directions, like seen with JFK.
A melon is not a good model for a human skull. The bullet does not impart much forward momentum to the melon in penetrating the melon. Also the melon is not free to move forward. A melon sitting on a wet level ice surface with hard bone strapped to it for the bullet to pass through on entry would provide a better model.
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?? How is "jet-effect" not "good old-fashioned physics"? It is just conservation of momentum. Alvarez did not go beyond Newton's laws in explaining it.
In his calculations, Alvarez omitted the most significant force acting on JFK's head at the time - the initial impact of the bullet on the back of the skull. The omission of this most fundamental force in his calculations renders his results invalid.
Wecht and Aguilar point out the following in an article entitled, "NOVA’s Cold Case: JFK - the Junk Science Behind PBS’s Recent Foray into the Crime of the Century", from 2016
Josiah Thompson, Ph.D. recently got the photo file of Alvarez’s shooting tests from a former Berkeley grad student who had participated in the tests, Paul Hoch, Ph.D. When he reviewed the images, Thompson discovered, as we describe, that the Nobel Laureate had misrepresented his own results: virtually all the objects he fired at flew away from the shooter, not toward him, except for the ones he reported in the AJP. Alvarez not only neglected to mention his inconvenient results, in the AJP he clearly implied there were none. (Paul Hoch never told anyone about his former professor’s contradictory results, despite having been asked about the tests for decades.)
The deliberate omission of these results renders his whole theory, as a scientific examination, invalid
Another problem for the Jet Effect theory is that the Z-film actually did record a couple of "jets" of material exiting the top of JFK's head at the moment of the head-shot. The problem is that these jets were not travelling in a direction that would have thrown JFK's head back and to the left.
In the Z-frame below I have picked out these two "jets" of material with arrows:
(https://i.postimg.cc/qq1bNBdL/z313-4.jpg) (https://postimages.org/)
In the frame below, the yellow line represents the line running through the top of his head. This is my own rough estimation and is made to give a general idea of the direction of the "Jets" (marked in red).
(https://i.postimg.cc/xCwxHpkk/z313-3.jpg) (https://postimages.org/)
Any Jet Effect would push JFK's head downwards rather than backwards.
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Well, good, I finally have someone to talk over 'old-fashioned physics' with.
How to you explain the motion of JFK's head, during z312-z318. This motion is detailed in Josiah Thompson's book "Six Seconds in Dallas", not by Josiah Thompson but by Physics graduate student William Hoffman. In Hoffman's data:
from z312-z313: The head moves forward at 2 mph.
from z313-z318: The head starts to move backwards, gradually moving faster and faster, reaching a maximum speed of 1.9 mph at z318.
How does a frontal shot explain this?
Why would it cause an initial movement of the head forward?
And when the backward movement starts, why does the speed gradually accelerated? Why wouldn't the bullet passing through the head transfer all it's momentum with 1 to 2 milliseconds, but instead transfer it's momentum over the course of 200 milliseconds?
By the way, the acceleration of the limousine does not explain this. William Hoffman, back in 1966, was way ahead of everyone. He also plotted the speed of the limousine and the acceleration of the limousine is not even a tenth of the amount of accelerated needed to explain the backwards movement of JFK's head.
* * * * *
Also, it is not proper science, when looking into a problem to declare some theories are 'unnecessary contrivances' and should not be considered. "The theory of Continental Drift is an unnecessary contrivance, and must not be considered a possible explanation for why an animal specie from the distance past appears to have been on both sides of the Atlantic, now separated by thousands of miles".
And so it is not proper science, when looking into a problem to declare:
1. A shot from the front, is an unnecessary contrivance to explain the movement of JFK's head.
2. The 'Jet Effect', is an unnecessary contrivance to explain the movement of JFK's head.
3. The 'Neurological Spam', is an unnecessary contrivance to explain the movement of JFK's head.
All three theories must be considered. And since only the "Neurological Spam' theory explains the movement of JFK's head, it is the theory that should be accepted as the one most probably true. Unless future data collected requires a reassessment". Like video of a taped melon reversing direction. Or video of a bullet striking a target and causing the target to gradually accelerate over the course of 200 milliseconds, or a fifth of a second. But until such a time, the "Neurological Spam' theory is the one I am going to go with.
Also, it is not proper science, when looking into a problem to declare some theories are 'unnecessary contrivances' and should not be considered.
Hi Joe, I'm certainly not suggesting these things shouldn't be considered and I accept the term "contrivance" might appear a little harsh. What I meant by this was that when the "back and to the left" movement came into the public sphere there was a need, for those who were putting forward a shot from behind, to come up with an explanation for how a shot from behind could cause such a movement.
It seemed very intuitive to accept that such a movement could only have been caused by a shot from the right front, which screamed CONSPIRACY, and an answer needed to be found quickly.
"Neurological spasm" and the "Jet Effect" were born out of this need for an explanation.
How to you explain the motion of JFK's head, during z312-z318. This motion is detailed in Josiah Thompson's book "Six Seconds in Dallas", not by Josiah Thompson but by Physics graduate student William Hoffman. In Hoffman's data:
from z312-z313: The head moves forward at 2 mph.
from z313-z318: The head starts to move backwards, gradually moving faster and faster, reaching a maximum speed of 1.9 mph at z318.
How does a frontal shot explain this?
Why would it cause an initial movement of the head forward?
And when the backward movement starts, why does the speed gradually accelerated? Why wouldn't the bullet passing through the head transfer all it's momentum with 1 to 2 milliseconds, but instead transfer it's momentum over the course of 200 milliseconds?
How does a frontal shot explain this?
It doesn't.
Why would it cause an initial movement of the head forward?
It wouldn't
In my opinion, the backwards head movement isn't caused by a bullet from the front passing through his head.
1. A shot from the front, is an unnecessary contrivance to explain the movement of JFK's head.
2. The 'Jet Effect', is an unnecessary contrivance to explain the movement of JFK's head.
3. The 'Neurological Spam', is an unnecessary contrivance to explain the movement of JFK's head.
All three theories must be considered. And since only the "Neurological Spam' theory explains the movement of JFK's head, it is the theory that should be accepted as the one most probably true.
It is only "probably true" if these are the only possible options.
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In his calculations, Alvarez omitted the most significant force acting on JFK's head at the time - the initial impact of the bullet on the back of the skull. The omission of this most fundamental force in his calculations renders his results invalid.
Alvarez did NOT ignore the impact of the bullet. He showed that the momentum ejected matter can exceed the momentum of the incoming bullet and drive the head backward (from his article: 44 Am. J. Phys. Vol 814 (http://dufourlaw.com/JFK/Alvarez.pdf), at page 819):
- I concluded that the retrograde motion of the President's head, in response to the rifle bullet shot, is consistent with the law of conservation of momentum, if one pays attention to the law of conservation of energy as well, and includes the momentum of all the material in the problem. The simplest way to see where I differ from most of the critics is to note that they treat the problem as though it involved only two interacting masses: the bullet and the head. My analysis involves three interacting masses, the bullet, the jet of brain matter observable in frame 313, and the remaining part of the head. It will turn out that the jet can carry forward more momentum than was brought in by the bullet, and the head recoils backward, as a rocket recoils when its jet fuel is ejected.
Wecht and Aguilar point out the following in an article entitled, "NOVA’s Cold Case: JFK - the Junk Science Behind PBS’s Recent Foray into the Crime of the Century", from 2016
Josiah Thompson, Ph.D. recently got the photo file of Alvarez’s shooting tests from a former Berkeley grad student who had participated in the tests, Paul Hoch, Ph.D. When he reviewed the images, Thompson discovered, as we describe, that the Nobel Laureate had misrepresented his own results: virtually all the objects he fired at flew away from the shooter, not toward him, except for the ones he reported in the AJP. Alvarez not only neglected to mention his inconvenient results, in the AJP he clearly implied there were none. (Paul Hoch never told anyone about his former professor’s contradictory results, despite having been asked about the tests for decades.)
The deliberate omission of these results renders his whole theory, as a scientific examination, invalid
It is important to use something that resembles a human skull. The skull does two things that cause the jet effect that a melon cannot do: 1. the hard bone of the back of the skull flattens the bullet on entry so that it pushes material in its path in passing through the soft interior part of the skull and 2. the skull is a rigid enclosure for the brain so the pressure builds up in the skull as the bullet passes through. The melon does not replicate the skull.
The jet effect is real. The best demonstration of the jet effect was done several years ago by Chad Zimmerman. Chad fired a 6.5 mm jacketed WC bullet from his Mannlicher-Carcano rifle into a suspended turkey. He strapped pork ribs to the entry side of the turkey (the left side) to simulate the skull bone.
Now, it was a big turkey much heavier than a human head and it did not move forward noticeably from the impact of the bullet, possibly due to the mass of the turkey and due to the shot being off-centre causing rotation of the turkey. But the rearward motion, due to the massive explosion of matter, is rapid and obvious. I have taken his video frames and slowed down the first 4 frames (2 sec. per frame) and the final frames at .5 seconds per frame so you can see the direction that the turkey moves from the explosive ejection of matter:
(http://dufourlaw.com/JFK/Chad_Zimmerman_Turkey_Shoot_Jeteffect.gif)
The original video is here:
http://dufourlaw.com/JFK/turkeyribshot1a.mpg (http://dufourlaw.com/JFK/turkeyribshot1a.mpg)
Another problem for the Jet Effect theory is that the Z-film actually did record a couple of "jets" of material exiting the top of JFK's head at the moment of the head-shot. The problem is that these jets were not travelling in a direction that would have thrown JFK's head back and to the left.
In the Z-frame below I have picked out these two "jets" of material with arrows:
(https://i.postimg.cc/qq1bNBdL/z313-4.jpg) (https://postimages.org/)
In the frame below, the yellow line represents the line running through the top of his head. This is my own rough estimation and is made to give a general idea of the direction of the "Jets" (marked in red).
(https://i.postimg.cc/xCwxHpkk/z313-3.jpg) (https://postimages.org/)
Any Jet Effect would push JFK's head downwards rather than backwards.
That is not a problem at all. The leftward-rearward momentum imparted to the head is equal and opposite to the rightward/forward component of momentum of the ejected matter. Almost all of that matter goes forward and it exits outward from the right side of his head. The only matter that does not impart a rearward/leftward impulse to the head is matter travelling at right angles to the rearward/leftward direction. A body ejected with momentum p at a direction 45 degrees to horizontal imparts a horizontal component of momentum equal to .707p (cosine of 45 degrees).
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The forward bullet momentum is imparted to the head before the head explodes so the head is driven forward before it is driven backward. One has to take into account that the rearward momentum imparted by the exploding matter from the head first had to stop the head from going forward. It is already accelerating rearward in z313.
There are two problems I have.
One. As I understand it, the Law on the Conservation of Momentum is an absolute law. It must be adhered to millisecond to millisecond. Instant to instant. It's not like a checking account with overdraft protection. It can never be, even temporarily, even for just 55 millisecond, or 1 millisecond, "Out of balance".
Two. During z312-z313, there was (according to you, if I understand you correctly) the momentum of:
1. The head moving forward.
2. The forward momentum of the bullet fragments, which all three fragments together still have about half the momentum of the pristine bullet.
3. The forward momentum of organic material flying forward which we can see in z313.
You seem to imply that this would put the momentum out of balance. And it would take time for the head to stop it's forward movement and start moving backwards. Only after the head started moving backwards, would the overall momentum of the head, bullet fragments and organic material get back in balance, that is be equal to the momentum of the pristine bullet.
My 'High School' understanding of Classical Newtonian Physics (my knowledge of Physics only comes from a course in high school from an excellent teacher) is that this is in error. Conservation of Momentum must be maintained millisecond to millisecond. Instant to Instant. It can never be temporarily out of balance. And so "It takes time for the forward motion to slow down and stop", "It takes time for the backwards momentum to reverse" cannot be true.
If the 'Jet Effect' is true, JFK's head would have moved forward, at most, about 0.4 inches (1 cm) during the first 10 mm, the longest Dr. Ken Rahn thought the explosion of the head could be delayed. At that point, the head would explode and organic material would be moving forward. Requiring the head to start moving backwards, immediately. But instead of seeing this, frames z312 and z313 shows that the head moved forward a full 2 inches (5 cm). Consistent with the organic material having a small amount of forward momentum (it clearly had some) but not enough to reverse the direction of movement or to even slow down the forward movement very much. Only when the muscles of JFK's body started to contract would this backwards movement of the head start.
Note: Regardless of how long Dr. Ken Rahn thought the head explosion could be delayed, z313 shows the head explosion occurred very early. The 'Harper fragment' being seen as a series of 'dots' two to four feet from JFK's head shows the head exploded very early on, just after the shutter closed on z312. The head should have been moving backwards at the time the shutter opened for z313 if the 'Jet Effect' was true.
A melon is not a good model for a human skull. The bullet does not impart much forward momentum to the melon in penetrating the melon. Also the melon is not free to move forward. A melon sitting on a wet level ice surface with hard bone strapped to it for the bullet to pass through on entry would provide a better model.
Then I would like to see a film of a better model of a human head being shot, moving forward two inches, and then reversing direction starting 55 milliseconds after the bullet strikes. Some good experiment that can lead me into believing the 'Jet Effect' theory might be true in the case of the JFK assassination.
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The video posted in the OP has no bearing on JFK's head-shot.
JFK's head explodes as a result of the shot. Pieces of his skull are blown in various directions. Jets of material, possibly brain matter and skull, are seen emanating from the top of his head. The top of his head literally blows off as a result of the shot.
To imagine there is no significant transfer of momentum from the bullet to the head in this instance is ludicrous.
The force required to achieve this incredible amount of damage would surely be reflected in how JFK's head moves as a result of this impact.
Neurological spasm and the jet effect are unnecessary contrivances when coming to explain the "back and to the left" movement of JFK as a result of the head-shot.
Good, old-fashioned physics is more than sufficient.
Good, old-fashioned physics is more than sufficient.
The jet-effect thingy is quite the good ol' physics that great grandpa had to beat out of rocks with other rocks back in the day. It's the kind of simple conservation of momentum problem handled in first semester freshman classical mechanics classes.
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There are two problems I have.
One. As I understand it, the Law on the Conservation of Momentum is an absolute law. It must be adhered to millisecond to millisecond. Instant to instant. It's not like a checking account with overdraft protection. It can never be, even temporarily, even for just 55 millisecond, or 1 millisecond, "Out of balance".
Two. During z312-z313, there was (according to you, if I understand you correctly) the momentum of:
1. The head moving forward.
2. The forward momentum of the bullet fragments, which all three fragments together still have about half the momentum of the pristine bullet.
3. The forward momentum of organic material flying forward which we can see in z313.
You seem to imply that this would put the momentum out of balance. And it would take time for the head to stop it's forward movement and start moving backwards. Only after the head started moving backwards, would the overall momentum of the head, bullet fragments and organic material get back in balance, that is be equal to the momentum of the pristine bullet.
My 'High School' understanding of Classical Newtonian Physics (my knowledge of Physics only comes from a course in high school from an excellent teacher) is that this is in error. Conservation of Momentum must be maintained millisecond to millisecond. Instant to Instant. It can never be temporarily out of balance. And so "It takes time for the forward motion to slow down and stop", "It takes time for the backwards momentum to reverse" cannot be true.
If the 'Jet Effect' is true, JFK's head would have moved forward, at most, about 0.4 inches (1 cm) during the first 10 mm, the longest Dr. Ken Rahn thought the explosion of the head could be delayed. At that point, the head would explode and organic material would be moving forward. Requiring the head to start moving backwards, immediately. But instead of seeing this, frames z312 and z313 shows that the head moved forward a full 2 inches (5 cm). Consistent with the organic material having a small amount of forward momentum (it clearly had some) but not enough to reverse the direction of movement or to even slow down the forward movement very much. Only when the muscles of JFK's body started to contract would this backwards movement of the head start.
Note: Regardless of how long Dr. Ken Rahn thought the head explosion could be delayed, z313 shows the head explosion occurred very early. The 'Harper fragment' being seen as a series of 'dots' two to four feet from JFK's head shows the head exploded very early on, just after the shutter closed on z312. The head should have been moving backwards at the time the shutter opened for z313 if the 'Jet Effect' was true.
Then I would like to see a film of a better model of a human head being shot, moving forward two inches, and then reversing direction starting 55 milliseconds after the bullet strikes. Some good experiment that can lead me into believing the 'Jet Effect' theory might be true in the case of the JFK assassination.
Actually, Joe, you are exactly correct about the jet effect's inapplicability in this case, and for the reasons you've mentioned.
There are two issues that never get mentioned on the subject of JFK's movement post-312.
First is gravity. That may seem like a ridiculous thing to bring up, but it's an ever-present force. One of considerable magnitude. A number of witnesses described JFK as "slumping" to his left. The Muchmore and Bronson films show that JFK was leaning well over to his left at the time he was hit in the head. Just considering gravity, the left part of "back and to the left" makes perfect sense.
The second comes in the form of Jacqueline Kennedy, who is holding on to JFKs left arm at 312. She's also moving her head forward around his elbow, as if the left arm is in her way and she's trying to see her husband's face. Given that she's already got a grip on his arm, it's a natural expectation that she would be pulling his elbow back to facilitate her view. So that when bullet struck and the lights went out, JFK would have been pulled by his wife back and to the left.
Tying these two together, if you look carefully at the z-film, you can see where JFK starts to shift to the left. It starts just after frame 255. Maybe this is just a coincidence, but Jackie grabs JFK's upper arm with her right hand at z245 and his left elbow with her left hand at z255. JFK's movement after the last shot may simply be the result of his wife trying to pull her towards him.
It's obvious once you look, but I never see this get brought up.
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Actually, Joe, you are exactly correct about the jet effect's inapplicability in this case, and for the reasons you've mentioned.
There are two issues that never get mentioned on the subject of JFK's movement post-312.
First is gravity. That may seem like a ridiculous thing to bring up, but it's an ever-present force. One of considerable magnitude. A number of witnesses described JFK as "slumping" to his left. The Muchmore and Bronson films show that JFK was leaning well over to his left at the time he was hit in the head. Just considering gravity, the left part of "back and to the left" makes perfect sense.
The second comes in the form of Jacqueline Kennedy, who is holding on to JFKs left arm at 312. She's also moving her head forward around his elbow, as if the left arm is in her way and she's trying to see her husband's face. Given that she's already got a grip on his arm, it's a natural expectation that she would be pulling his elbow back to facilitate her view. So that when bullet struck and the lights went out, JFK would have been pulled by his wife back and to the left.
Tying these two together, if you look carefully at the z-film, you can see where JFK starts to shift to the left. It starts just after frame 255. Maybe this is just a coincidence, but Jackie grabs JFK's upper arm with her right hand at z245 and his left elbow with her left hand at z255. JFK's movement after the last shot may simply be the result of his wife trying to pull her towards him.
It's obvious once you look, but I never see this get brought up.
Mitch
I agree. I think JFK was leaning to the left. It appears Jackie was pushing Jack's left elbow down, to get a better view of his face to see what was the matter. With his arms being fairly rigid due to the neck wound, that would rotate the torso some to the left.
We don't know how Jackie affected JFK's movement during z312-z318.
JFK was sitting pretty upright. So gravity wouldn't have had much of an effect, at least before z317. Before z317, the acceleration of JFK's head was up to 0.25 G's. JFK would have to be tilted back by around 15 degrees to get that amount of acceleration ( 1 G * sin(15) ). I don't think he was tilted back nearly that much. If anything, he was leaning forward some at z312. JFK's backwards acceleration was not caused by gravity. Nor by the way too small acceleration of the limousine during that time, that was practically moving at a steady speed.
But we know that not all of JFK's post z312 movement was caused by Jackie. At z-316 through z-318, JFK's right elbow suddenly j-e-r-k-s up 6 inches, than falls limply down. That is clearly caused by a neurological spasm.
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Mitch
I agree. I think JFK was leaning to the left. It appears Jackie was pushing Jack's left elbow down, to get a better view of his face to see what was the matter. With his arms being fairly rigid due to the neck wound, that would rotate the torso some to the left.
We don't know how Jackie affected JFK's movement during z312-z318.
JFK was sitting pretty upright. So gravity wouldn't have had much of an effect, at least before z317. Before z317, the acceleration of JFK's head was up to 0.25 G's. JFK would have to be tilted back by around 15 degrees to get that amount of acceleration ( 1 G * sin(15) ). I don't think he was tilted back nearly that much. If anything, he was leaning forward some at z312. JFK's backwards acceleration was not caused by gravity. Nor by the way too small acceleration of the limousine during that time, that was practically moving at a steady speed.
But we know that not all of JFK's post z312 movement was caused by Jackie. At z-316 through z-318, JFK's right elbow suddenly j-e-r-k-s up 6 inches, than falls limply down. That is clearly caused by a neurological spasm.
Look at the Muchmore film, which shows the amount of lean most clearly. JFK is leaning to the left much more than you think. And yes, I just had to say it that way. This is about five frames before the last shot:
(http://i.ytimg.com/vi/yKqWozXc4KY/maxresdefault.jpg)
BTW, I'm not putting the whole kitty on one cause or another. Just that there are forces acting on JFK that ought to be considered, but never seem to be.
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Look at the Muchmore film, which shows the amount of lean most clearly. JFK is leaning to the left much more than you think. And yes, I just had to say it that way. This is about five frames before the last shot:
(http://i.ytimg.com/vi/yKqWozXc4KY/maxresdefault.jpg)
BTW, I'm not putting the whole kitty on one cause or another. Just that there are forces acting on JFK that ought to be considered, but never seem to be.
My impression from the Zapruder film alone, which is mostly the film I look at, gave me the impression that JFK was leaning to the left before z312. The Muchmore frame that you provides proves that JFK was leaning to the left, even more than I realized.
I now think that gravity could have been an important part of JFK's movement during z312-z316. But not backwards. JFK was sitting too upright for that. If anything he was leaning forward during z312-z316. But definitely, gravity could have caused him to start falling to the left during that time period. The lean to the left was pretty pronounced. But that has little impact on the Hoffman data and shows that something was continuously accelerating JFK's head backwards from z313-z318. It wasn't gravity, it wasn't the very small acceleration of the limousine during this period. These accelerations were too small to cause the amount of backwards acceleration of JFK's head, around a quarter of a G. It could only be caused by JFK's muscles. Which is also the only cause of JFK's elbow jerking up during z316-z318.
The Muchmore frame you provided is very helpful in establishing the pronounced lean of JFK to the left just before z312. Much more :) than the Zapruder film alone provides.
Note: I first typed in the previous line in full, except for the smiley face, before realizing it makes for a pretty good pun.
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There are two problems I have.
One. As I understand it, the Law on the Conservation of Momentum is an absolute law. It must be adhered to millisecond to millisecond. Instant to instant. It's not like a checking account with overdraft protection. It can never be, even temporarily, even for just 55 millisecond, or 1 millisecond, "Out of balance".
Two. During z312-z313, there was (according to you, if I understand you correctly) the momentum of:
1. The head moving forward.
2. The forward momentum of the bullet fragments, which all three fragments together still have about half the momentum of the pristine bullet.
3. The forward momentum of organic material flying forward which we can see in z313.
It is not a simple physics problem to analyze. The impulse from the bullet and the impulse from the exploding exit wound are not in directly opposite directions. And the impulses occur at slightly different times (the time between the impact to the back of the head and the time the head opens up to release the pressure). We don't know how much time that took. In order to release that matter, the skull has to start moving out of the way. And the release of pressure/explosion is not instantaneous. It continues as the skull opens up. The different directions of these impulses affect the body differently.
In any event, we are only seeing a 25 ms. window every 55 ms. In z313 the head is certainly experiencing a force from the exploding exit wound but not from the bullet. It is, therefore, accelerating in the direction of the force imparted by that exiting matter.
Different directions: The bullet momentum imparted to the head is in the direction of the original bullet direction. But the impulse from the explosive exit wound is opposite to the direction of the exploding matter, which is not the original direction of the bullet. Brain matter explodes generally to the right and forward so the impulse will be in the leftward and rearward direction. It looks to me like the right side of his skull opens, not the forehead, so possibly the component of leftward force due to the explosive exit wound is greater than the rearward component.
Different response of body to forces in different directions: To complicate matters even further, the President was leaning forward and left and was turned to the left. The head is not equally free to move in all directions. It is easier to move the head forward than to move it sideways.
As the head moves sideways left from the explosion impulse it is going to take the body with it. The bullet impact causes the head pivot forward without taking the body. So it will take more time to see the head and body move in response to the explosive exit of matter from the head than to see head move in response to the bullet impact.
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Alvarez did NOT ignore the impact of the bullet. He showed that the momentum ejected matter can exceed the momentum of the incoming bullet and drive the head backward (from his article: 44 Am. J. Phys. Vol 814 (http://dufourlaw.com/JFK/Alvarez.pdf), at page 819):
- I concluded that the retrograde motion of the President's head, in response to the rifle bullet shot, is consistent with the law of conservation of momentum, if one pays attention to the law of conservation of energy as well, and includes the momentum of all the material in the problem. The simplest way to see where I differ from most of the critics is to note that they treat the problem as though it involved only two interacting masses: the bullet and the head. My analysis involves three interacting masses, the bullet, the jet of brain matter observable in frame 313, and the remaining part of the head. It will turn out that the jet can carry forward more momentum than was brought in by the bullet, and the head recoils backward, as a rocket recoils when its jet fuel is ejected.
It is a fact that Alvarez omitted the interaction of the incoming bullet with the skull, forcing JFK's head forward.
Not only that, as the fragments of bullet traveled through the brain tissue they eventually encountered the skull a second time - as the fragments exited the skull. This interaction also forced JFK's head forwards and this interaction is completely ignored in both Alvarez's experiments and calculations.
Both of the most significant transfer of momentum interactions are nowhere to be seen in the calculations.
Alvarez starts with a 10kg ballistic pendulum into which is fired a 10 gram bullet. From this he concludes that only 0.01% of the kinetic energy of the bullet is converted into mechanical energy upon striking the pendulum. The remaining 99.99% of the incoming kinetic energy is converted into heat.
This is easily calculated because the bullet remains in the wooden block, therefore all of it's kinetic energy is transmitted into the block in one form of energy or another.
What does this have to do with JFK's head-shot?
The answer is - absolutely nothing
It hardly needs pointing out that JFK's head is not a 10kg block of wood but that is not the real issue. When the bullet strikes JFK's head it breaks up, these fragments pass through the brain and exit the head. The majority of the bullet exits the head and is no longer a part of the head/bullet system. These fragments still have plenty of kinetic energy - one fragment cracks the windshield, one dents the chrome trim and others may have left the limo completely. All of this kinetic energy is lost to the head/bullet system whereas in the pendulum/bullet system all the kinetic energy is kept within the system because the bullet is retained in the block.
Alvarez's calculations are meaningless.
The thing is, Alvarez is aware of this discrepancy when he writes:
Ballistic pendulums are designed so that they contain the inelastically dissipated energy. Unfortunately, the human head is not able to contain the major fraction of the energy carried in.by the bullet. This tragic aspect of the assassination is clearly visible in frame 313 of the Zapruder film, and is discussed in detail in the reports of the autopsy surgeons.
However, in the very next sentence he makes it clear he is still applying his meaningless ballistic calculations to JFK's head-shot:
The mechanism of the retrograde recoil turns out to be rather simple, if one remembers that 99.9% of the incoming energy must be accounted for.
It is true Alvarez demonstrated that the momentum of the ejected matter could exceed the momentum of the bullet.
But he then concludes, for no given reason, that this ejected matter "gives the melon an equal and opposite momentum".
It's as though he assumes it is opposite because that is what he has already concluded. He seems to be saying that IF the jet of material provided opposite momentum, it could move JFK's head in the opposite direction to the that of the bullet simply because the momentum of the ejected matter is greater than the momentum of the bullet.
But the ejected matter is not competing with the momentum of the bullet, it is competing with the momentum of JFK's head.
Also, he provides no mechanism for why the matter is ejecting in the first place [in the case of any "jet effect" this has nothing to do with the transit of the bullet]. Nor does he allow for any of the ejected matter to be a result of the transit of the bullet.
His incredibly strained attempts to justify his thought process lead to bizarre statements such as this:
The melon would then recoil backward with about twice the velocity it would have been expected to go forward, assuming it were made of wood.
A melon made of wood??
It is important to use something that resembles a human skull. The skull does two things that cause the jet effect that a melon cannot do: 1. the hard bone of the back of the skull flattens the bullet on entry so that it pushes material in its path in passing through the soft interior part of the skull and 2. the skull is a rigid enclosure for the brain so the pressure builds up in the skull as the bullet passes through. The melon does not replicate the skull.
The jet effect is real. The best demonstration of the jet effect was done several years ago by Chad Zimmerman. Chad fired a 6.5 mm jacketed WC bullet from his Mannlicher-Carcano rifle into a suspended turkey. He strapped pork ribs to the entry side of the turkey (the left side) to simulate the skull bone.
Now, it was a big turkey much heavier than a human head and it did not move forward noticeably from the impact of the bullet, possibly due to the mass of the turkey and due to the shot being off-centre causing rotation of the turkey. But the rearward motion, due to the massive explosion of matter, is rapid and obvious. I have taken his video frames and slowed down the first 4 frames (2 sec. per frame) and the final frames at .5 seconds per frame so you can see the direction that the turkey moves from the explosive ejection of matter:
(http://dufourlaw.com/JFK/Chad_Zimmerman_Turkey_Shoot_Jeteffect.gif)
The original video is here:
http://dufourlaw.com/JFK/turkeyribshot1a.mpg (http://dufourlaw.com/JFK/turkeyribshot1a.mpg)
That is not a problem at all. The leftward-rearward momentum imparted to the head is equal and opposite to the rightward/forward component of momentum of the ejected matter. Almost all of that matter goes forward and it exits outward from the right side of his head. The only matter that does not impart a rearward/leftward impulse to the head is matter travelling at right angles to the rearward/leftward direction. A body ejected with momentum p at a direction 45 degrees to horizontal imparts a horizontal component of momentum equal to .707p (cosine of 45 degrees).
Almost all of that matter goes forward
In the graphic I posted the main "jet" of ejected matter goes backwards relative to the position of JFK's head, which would force JFK's head forwards and downwards. If it was part of the "jet effect". Which it isn't.
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Neurological Spasm and why I don't buy it.
As JFK passes behind the Stemmons sign his left arm is down by his side.
As he emerges from behind the sign his left arm is in the same position.
Suddenly, it rockets up from his side until both his arms are in this extreme position;
(https://i.postimg.cc/qv9T9cV2/z232-MPI-3.jpg) (https://postimg.cc/NK7SXH00)
It takes less than half a second to achieve this extreme posture, it is an incredibly rapid movement.
Both elbows appear to extended fully upwards in an extraordinary manner, his hands clench shut apart from the index finger of his left hand which points rigidly, his fists are balled up near his chin and he seems to sit bolt upright.
For the briefest moment he is held in this rigid, extreme posture before relaxing and slumping towards Jackie.
I believe this incredibly rapid movement and extreme posture are a reflex reaction, a neurological spasm, if you will, a feature of which is the stiffening of JFK's upper body.
However, when we examine the head-shot there appears to be no such rigidity present, JFK seems to flop around, his head and arm movement appear completely loose.
There are 16 neck muscles - 4 Suboccipital, 4 Suprahyoid, 4 Infrahyoid and 3 paired sets of Scalene muscles.
These control the various movements of the head - side to side, backwards/forwards and swiveling.
It is an incredibly complex part of the body.
If Neurological Spasm is present during the head-shot, I see no reason why, out of all the neck muscles, only the muscles involving the backwards movement of the head should be involved.
Also, going back to the first point, if these neck muscles were involved why wouldn't they hold the head in the backwards position. This is not shown in the Z-film.
You seem to be proposing a very brief triggering of some very specific muscles, which I, personally, don't buy.
Particularly when there is a far more straight-forward [IMO] explanation.
(https://i.postimg.cc/tJF858sd/Head-Shot-close.gif) (https://postimages.org/)
Different people see different things when analyzing the clip above.
I can only say what I see.
At the moment of the head-shot, the very first movement is forward.
JFK's head seems to nod forward and downward incredibly quickly and then rebound upwards and backwards.
At the moment of the head-shot JFK's head seems to be slumped forward, his chin resting against his body. The massive blow to the back of his head forces his head forwards and downwards, but, because it is already resting on his upper torso/lower neck, his head has nowhere to go and simply rebounds upwards.
No jet effect.
No neurological spasm.
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It is a fact that Alvarez omitted the interaction of the incoming bullet with the skull, forcing JFK's head forward.
Not only that, as the fragments of bullet traveled through the brain tissue they eventually encountered the skull a second time - as the fragments exited the skull. This interaction also forced JFK's head forwards and this interaction is completely ignored in both Alvarez's experiments and calculations.
Both of the most significant transfer of momentum interactions are nowhere to be seen in the calculations.
I am not sure why you think he did not take it into account. If the bullet imparted momentum to the skull on exit, it had to have imparted less than its total momentum on entry and while plowing through the head. It doesn't matter when during the interaction of bullet and head when momentum was transferred. His whole point was that the momentum from the explosion can easily exceed the total momentum of the incoming bullet so that the net movement is toward the shooter.
Alvarez states at p. 820 that the target moves toward the shooter if pj (momentum of the jet) exceeds pb (momentum of the bullet). He shows how he determined that 10% of the mass ejected at 10% of the bullet speed carries momentum that exceeds the bullet momentum.
Alvarez starts with a 10kg ballistic pendulum into which is fired a 10 gram bullet. From this he concludes that only 0.01% of the kinetic energy of the bullet is converted into mechanical energy upon striking the pendulum. The remaining 99.99% of the incoming kinetic energy is converted into heat.
This is easily calculated because the bullet remains in the wooden block, therefore all of it's kinetic energy is transmitted into the block in one form of energy or another.
What does this have to do with JFK's head-shot?
The answer is - absolutely nothing
Alvarez is using the example where there is no exploding exit wound to show that the momentum of the ballistic pendulum is, initially, in the direction of the bullet. That is how the bullet speed is determined: vbullet=vblock+bullet x Mblock+bullet/mbullet. The initial speed of the block + bullet is determined by measuring the height reached by the pendulum swing. He then compares that to a situation when the target explodes sending matter forward.
It hardly needs pointing out that JFK's head is not a 10kg block of wood but that is not the real issue. When the bullet strikes JFK's head it breaks up, these fragments pass through the brain and exit the head. The majority of the bullet exits the head and is no longer a part of the head/bullet system. These fragments still have plenty of kinetic energy - one fragment cracks the windshield, one dents the chrome trim and others may have left the limo completely. All of this kinetic energy is lost to the head/bullet system whereas in the pendulum/bullet system all the kinetic energy is kept within the system because the bullet is retained in the block.
The fragments do not carry much kinetic energy. If the bullet exited travelling at 400 fps it would have 1/25th of the original bullet energy, meaning 96% of the bullet energy was transferred to the head.
Alvarez's calculations are meaningless.
Alvarez took this all into account. In fact, he noted that even if you assume only 10% of the incoming kinetic energy is used to propel 10% of the mass of the target, the momentum of the expelled jet is 101/2 or over 3 times the momentum of the incoming bullet (p. 820):
"For example, if the bullet weighed 0.1 % of the melon weight, and if 10% of the incoming kinetic energy was used to propel 10% of the mass of the melon forward, then the momentum of the jet expelled forward would be (10)1/2 times that of the incoming bullet."
The thing is, Alvarez is aware of this discrepancy when he writes:
Ballistic pendulums are designed so that they contain the inelastically dissipated energy. Unfortunately, the human head is not able to contain the major fraction of the energy carried in.by the bullet. This tragic aspect of the assassination is clearly visible in frame 313 of the Zapruder film, and is discussed in detail in the reports of the autopsy surgeons.
However, in the very next sentence he makes it clear he is still applying his meaningless ballistic calculations to JFK's head-shot:
The mechanism of the retrograde recoil turns out to be rather simple, if one remembers that 99.9% of the incoming energy must be accounted for.
It is true Alvarez demonstrated that the momentum of the ejected matter could exceed the momentum of the bullet.
But he then concludes, for no given reason, that this ejected matter "gives the melon an equal and opposite momentum".
It's as though he assumes it is opposite because that is what he has already concluded. He seems to be saying that IF the jet of material provided opposite momentum, it could move JFK's head in the opposite direction to the that of the bullet simply because the momentum of the ejected matter is greater than the momentum of the bullet.
But the ejected matter is not competing with the momentum of the bullet, it is competing with the momentum of JFK's head.
That is a fair point. He is assuming that the ejected matter from the melon or head was in the direction of the incoming bullet. That is how he set up his melons. I agree that the situation with JFK was a bit different. Since the matter explodes out of the right side of his head in many directions, the directions of ejecta and incoming bullet are not quite the same.
Also, he provides no mechanism for why the matter is ejecting in the first place [in the case of any "jet effect" this has nothing to do with the transit of the bullet]. Nor does he allow for any of the ejected matter to be a result of the transit of the bullet.
It doesn't matter what the mechanism is. We can see the exploding exit wound. It is obvious that it is caused by energy imparted to the head by the bullet. All that matters is the direction it is moving, how fast it is moving and its mass. This is about physics, not biology.
His incredibly strained attempts to justify his thought process lead to bizarre statements such as this:
The melon would then recoil backward with about twice the velocity it would have been expected to go forward, assuming it were made of wood.
A melon made of wood??
You are not interpreting it correctly. Instead of "assuming" read "if". He is comparing the movement of the melon after the explosive exit of matter in the direction of the bullet and comparing it to how a wooden object of the same size and mass would move (ie. with no jet of matter being ejected).
In the graphic I posted the main "jet" of ejected matter goes backwards relative to the position of JFK's head, which would force JFK's head forwards and downwards. If it was part of the "jet effect". Which it isn't.
Was JFK exempt from the laws of physics?
We can see the matter exploding from his head. There is a visible piece of matter seen in z313 with a streak from above the head to a point that is at least a metre from the starting point. (Note: the fine spray did not penetrate into the air mass above the car as rapidly. But the initial acceleration and its velocity coming out of the head would have been similar, and it is that velocity immediately on leaving the head that provides the impulse).
Since we can see that streak is at least 1 m long and was created during the exposure of 25 ms. (the frame exposure time determined by Zavada), the jet travelled away from the head at a speed of about 1 m in 25 ms. That is a speed of 40 m/s. And that assumes that the streak is not angled toward or away from the camera.
Only 150 grams of matter at that speed carries the same momentum as the maximum momentum carried by the bullet (and we know that the bullet did not impart all its momentum to the head because the bulk of it exited).
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I am not sure why you think he did not take it into account. If the bullet imparted momentum to the skull on exit, it had to have imparted less than its total momentum on entry and while plowing through the head. It doesn't matter when during the interaction of bullet and head when momentum was transferred. His whole point was that the momentum from the explosion can easily exceed the total momentum of the incoming bullet so that the net movement is toward the shooter.
Alvarez states at p. 820 that the target moves toward the shooter if pj (momentum of the jet) exceeds pb (momentum of the bullet). He shows how he determined that 10% of the mass ejected at 10% of the bullet speed carries momentum that exceeds the bullet momentum.
Alvarez is using the example where there is no exploding exit wound to show that the momentum of the ballistic pendulum is, initially, in the direction of the bullet. That is how the bullet speed is determined: vbullet=vblock+bullet x Mblock+bullet/mbullet. The initial speed of the block + bullet is determined by measuring the height reached by the pendulum swing. He then compares that to a situation when the target explodes sending matter forward.
The fragments do not carry much kinetic energy. If the bullet exited travelling at 400 fps it would have 1/25th of the original bullet energy, meaning 96% of the bullet energy was transferred to the head.
Alvarez took this all into account. In fact, he noted that even if you assume only 10% of the incoming kinetic energy is used to propel 10% of the mass of the target, the momentum of the expelled jet is 101/2 or over 3 times the momentum of the incoming bullet (p. 820):
"For example, if the bullet weighed 0.1 % of the melon weight, and if 10% of the incoming kinetic energy was used to propel 10% of the mass of the melon forward, then the momentum of the jet expelled forward would be (10)1/2 times that of the incoming bullet."
That is a fair point. He is assuming that the ejected matter from the melon or head was in the direction of the incoming bullet. That is how he set up his melons. I agree that the situation with JFK was a bit different. Since the matter explodes out of the right side of his head in many directions, the directions of ejecta and incoming bullet are not quite the same.
It doesn't matter what the mechanism is. We can see the exploding exit wound. It is obvious that it is caused by energy imparted to the head by the bullet. All that matters is the direction it is moving, how fast it is moving and its mass. This is about physics, not biology.
You are not interpreting it correctly. Instead of "assuming" read "if". He is comparing the movement of the melon after the explosive exit of matter in the direction of the bullet and comparing it to how a wooden object of the same size and mass would move (ie. with no jet of matter being ejected).
Was JFK exempt from the laws of physics?
We can see the matter exploding from his head. There is a visible piece of matter seen in z313 with a streak from above the head to a point that is at least a metre from the starting point. (Note: the fine spray did not penetrate into the air mass above the car as rapidly. But the initial acceleration and its velocity coming out of the head would have been similar, and it is that velocity immediately on leaving the head that provides the impulse).
Since we can see that streak is at least 1 m long and was created during the exposure of 25 ms. (the frame exposure time determined by Zavada), the jet travelled away from the head at a speed of about 1 m in 25 ms. That is a speed of 40 m/s. And that assumes that the streak is not angled toward or away from the camera.
Only 150 grams of matter at that speed carries the same momentum as the maximum momentum carried by the bullet (and we know that the bullet did not impart all its momentum to the head because the bulk of it exited).
His whole point was that the momentum from the explosion
Explosion?
Where does he mention an explosion?
It doesn't matter what the mechanism is.
How so?
It's the fundamental point Alvarez is supposedly demonstrating.
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His whole point was that the momentum from the explosion
Explosion?
Where does he mention an explosion?
He refers to the release of matter from the head as a "jet" or "explosive jet effect". See his footnote 13 where he states:
"13 The fact that the bullets were soft nosed, rather than fully jacketed (as the Mannlicher-Carcano bullets were), was apparently important in intensifying the explosive jet effect."
. We can see that it is more of an explosion in a wide range of directions rather than a directed jet. But the effect is the same: the head recoils with momentum equal in magnitude and opposite in direction to the total momentum of the ejected matter.
It doesn't matter what the mechanism is.
How so?
It's the fundamental point Alvarez is supposedly demonstrating.
I am not sure why you think that the mechanism is important. We can see the explosive exit wound. Alvarez was trying to compare the momentum of the "jet" to the momentum of the bullet. All he needs to know is how much momentum the bullet transferred to the head.
The bullet is transferring momentum when it slows down. The amount of momentum transferred is: bullet mass x change in bullet velocity from the entry to the exit of the bullet. Alvarez just assumed the maximum (ie. all) bullet momentum was transferred to the head. Using a estimates of velocity and mass of the ejecta, he showed that the momentum of the ejected matter (which is equal to the impulse to the head in the opposite direction) could easily exceed the maximum bullet momentum.
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Neurological Spasm and why I don't buy it.
As JFK passes behind the Stemmons sign his left arm is down by his side.
As he emerges from behind the sign his left arm is in the same position.
Suddenly, it rockets up from his side until both his arms are in this extreme position;
(https://i.postimg.cc/qv9T9cV2/z232-MPI-3.jpg) (https://postimg.cc/NK7SXH00)
It takes less than half a second to achieve this extreme posture, it is an incredibly rapid movement.
Both elbows appear to extended fully upwards in an extraordinary manner, his hands clench shut apart from the index finger of his left hand which points rigidly, his fists are balled up near his chin and he seems to sit bolt upright.
For the briefest moment he is held in this rigid, extreme posture before relaxing and slumping towards Jackie.
I believe this incredibly rapid movement and extreme posture are a reflex reaction, a neurological spasm, if you will, a feature of which is the stiffening of JFK's upper body.
However, when we examine the head-shot there appears to be no such rigidity present, JFK seems to flop around, his head and arm movement appear completely loose.
There are 16 neck muscles - 4 Suboccipital, 4 Suprahyoid, 4 Infrahyoid and 3 paired sets of Scalene muscles.
These control the various movements of the head - side to side, backwards/forwards and swiveling.
It is an incredibly complex part of the body.
If Neurological Spasm is present during the head-shot, I see no reason why, out of all the neck muscles, only the muscles involving the backwards movement of the head should be involved.
Also, going back to the first point, if these neck muscles were involved why wouldn't they hold the head in the backwards position. This is not shown in the Z-film.
You seem to be proposing a very brief triggering of some very specific muscles, which I, personally, don't buy.
Particularly when there is a far more straight-forward [IMO] explanation.
(https://i.postimg.cc/tJF858sd/Head-Shot-close.gif) (https://postimages.org/)
Different people see different things when analyzing the clip above.
I can only say what I see.
At the moment of the head-shot, the very first movement is forward.
JFK's head seems to nod forward and downward incredibly quickly and then rebound upwards and backwards.
At the moment of the head-shot JFK's head seems to be slumped forward, his chin resting against his body. The massive blow to the back of his head forces his head forwards and downwards, but, because it is already resting on his upper torso/lower neck, his head has nowhere to go and simply rebounds upwards.
No jet effect.
No neurological spasm.
Hi Dan. I totally agree that there's no jet effect, but I do believe that
JFK convulsed when the fatal shot was fired.
In 1978, during an interview with the HSCA, SS Agent Sam Kinney said that when they were trying to remove JFK from the limousine, JFK's feet were "locked under (Governor Connally's) jump seat".
To me, this indicates that JFK convulsed as soon as his brain was destroyed.
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Hi Dan. I totally agree that there's no jet effect, but I do believe that
JFK convulsed when the fatal shot was fired.
You cannot conclude that the explosion of matter from the head (some of which landed on the hood of the car and pieces of which landed on the street) did not result in an equal and opposite impulse to the head. So the question I would have is: how did you determine that the impulse from the ejection of matter from the head was not sufficient to cause the body to move left and to the rear?
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You cannot conclude that the explosion of matter from the head (some of which landed on the hood of the car and pieces of which landed on the street) did not result in an equal and opposite impulse to the head. So the question I would have is: how did you determine that the impulse from the ejection of matter from the head was not sufficient to cause the body to move left and to the rear?
Perhaps I'm in error. Perhaps the matter being ejected from the top of the head did contribute to the backward movement. Not being an expert in the field of what our brain is capable of doing when severely damaged as in this case, however, it makes more sense that the convulsion JFK obviously suffered is the main contributor of the upper body suddenly going backwards during the fatal shot to the head. Furthermore, There is absolutely no proof that JFK's body moved to the left as a result of the bullet striking his head. He was already "leaning noticeably to his left".
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Perhaps I'm in error. Perhaps the matter being ejected from the top of the head did contribute to the backward movement. Not being an expert in the field of what our brain is capable of doing when severely damaged as in this case, however, it makes more sense that the convulsion JFK obviously suffered is the main contributor of the upper body suddenly going backwards during the fatal shot to the head. Furthermore, There is absolutely no proof that JFK's body moved to the left as a result of the bullet striking his head. He was already "leaning noticeably to his left".
It is a reasonable inference that his body moved as it did because he had been shot. The evidence shows that a bullet entered the back of the head and exited as we see in the film. There is no evidence of any other impact. So there is no need to prove "jet effect" or "neurological spasm" or a combination of both as the cause of that movement. But if is definitely because he was hit by a bullet from the rear.
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It is a reasonable inference that his body moved as it did because he had been shot. The evidence shows that a bullet entered the back of the head and exited as we see in the film. There is no evidence of any other impact. So there is no need to prove "jet effect" or "neurological spasm" or a combination of both as the cause of that movement. But if is definitely because he was hit by a bullet from the rear.
Correct. He was struck in the back of the head by a singular bullet. I've been saying it for years, and years.
The one and only reason for there being any argument about the bullet coming from above and behind is due to the conspiracy theorists whom, since 1964, have argued that the bullet or a second bullet struck him in the head from the front, from the direction of the knoll. Therefore, this-and this alone--is the reason for discussing the "Jet Effect" and/or the Neuro-muscular reaction. Those of us who accept the work by the experts in forensics and ballistics, plus using common sense see no need to argue that a singular bullet killed JFK. With the addition of a document of the 1978 interview Sam Kinney stating that JFK's feet were locked under Connally's jump seat, this only adds further proof that as the fatal bullet struck JFK in the brain, he convulsed, causing his legs to also convulse and move forward, which caused his feet to go completely under Connally's jump seat to the point that they were "locked" under. This is the first bit of information regarding the body of JFK as the bullets struck, that prove that it was a convulsion that caused his upper body to move backwards against the seat at an estimated 103.3 MPH, not a bullet fired from the front or right side of the limousine.
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Correct. He was struck in the back of the head by a singular bullet. I've been saying it for years, and years.
The one and only reason for there being any argument about the bullet coming from above and behind is due to the conspiracy theorists whom, since 1964, have argued that the bullet or a second bullet struck him in the head from the front, from the direction of the knoll. Therefore, this-and this alone--is the reason for discussing the "Jet Effect" and/or the Neuro-muscular reaction. Those of us who accept the work by the experts in forensics and ballistics, plus using common sense see no need to argue that a singular bullet killed JFK. With the addition of a document of the 1978 interview Sam Kinney stating that JFK's feet were locked under Connally's jump seat, this only adds further proof that as the fatal bullet struck JFK in the brain, he convulsed, causing his legs to also convulse and move forward, which caused his feet to go completely under Connally's jump seat to the point that they were "locked" under. This is the first bit of information regarding the body of JFK as the bullets struck, that prove that it was a convulsion that caused his upper body to move backwards against the seat at an estimated 103.3 MPH, not a bullet fired from the front or right side of the limousine.
So long as one offers a plausible mechanism to explain the body's motion and so long as there is no evidence at all of a shot from the front right, that is all one needs. Introducing an uncertain mechanism to explain the body's motion is just giving fuel to the conspiracy fanatics.
I don't see how the feet being jammed under the front seat helps prove that there was a neuromuscular spasm. There is nothing to show that JFK did not put his feet there before the shot. There was not a lot of room between the seats. That would be especially so with Connally in front because he was quite tall and he would likely have pushed the seat back as far as it would go. Besides, wouldn't a push of the body upward from the feet push the feet down?
The recoil from the exploding head provides a mechanism based on the evidence of what we can actually observe (matter driven out of the head at high speed). The mechanism of a neuromuscular spasm due to catastrophic loss of brain matter from the right side (which controls the left side of the body) does not have sufficient basis in fact. It may be possible but we really can't say it occurred. We can, however, say based on what is observed in the zfilm, that the head received a left-rearward impulse from the matter exploding out of the front right side of his head.
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So long as one offers a plausible mechanism to explain the body's motion and so long as there is no evidence at all of a shot from the front right, introducing an uncertain mechanism to explain the body's motion is just giving fuel to the conspiracy fanatics.
I don't see how the feet being jammed under the front seat helps prove that there was a neuromuscular spasm. There is nothing to show that JFK did not put his feet there before the shot. There was not a lot of room between the seats. That would be especially so with Connally in front because he was quite tall and he would likely have pushed the seat back as far as it would go.
The recoil from the exploding head provides a mechanism based on the evidence of what we can actually observe (matter driven out of the head at high speed). The mechanism of a neuromuscular spasm due to catastrophic loss of brain matter from the right side (which controls the left side of the body) does not have sufficient basis in fact. It may be possible but we really can't say it occurred. We can, however, say based on what is observed in the zfilm, that the head received a left-rearward impulse from the matter exploding out of the front left side of his head.
I can! According to Kinney the feet were "locked". The only way JFK's feet could've been considered "locked" under that seat was if he'd shoved them up and under the seat, and locked them into that position himself, which I highly doubt that he did. And the jump seats were not capable of being moved by Connally any further than where they clicked into place once put into place. They were connected onto a track, and once locked into place, they could no further to the rear. You are correct that there wasn't much room between where JFK's feet could be situated and the jump seat. At least one photograph shows how tight of a squeeze there is between JFK's knees and the back rest of Connally' jump seat. One photograph during the motorcade shows JFK's knees about an inch away-if that- from the top of Connally's seat.
The explosion of head matter exited from TOP of the head--not the "left side"-- but the top. The left side of the skull was basically undamaged same as the brain-and only a fraction of the right top side of the skull was missing. Nearly the whole top of his head was gone, according to the top of the head autopsy photos. Not only can the top of JFK's head be seen flying through the air at a speed of around 80MPH (calculated by Dr. John Lattimer in his book) we can see the skull fragments in the Zapruder film in motion, and a large skull fragment can be seen in both Z 314 between JFK and the Connally's, but the same fragment is captured in later frames bouncing off the top rest of Nellie Connally's seat and tumbling towards the floor of the car.
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I can! According to Kinney the feet were "locked". The only way JFK's feet could've been considered "locked" under that seat was if he'd shoved them up and under the seat, and locked them into that position himself, which I highly doubt that he did. And the jump seats were not capable of being moved by Connally any further than where they clicked into place once put into place. They were connected onto a track, and once locked into place, they could no further to the rear. You are correct that there wasn't much room between where JFK's feet could be situated and the jump seat. At least one photograph shows how tight of a squeeze there is between JFK's knees and the back rest of Connally' jump seat. One photograph during the motorcade shows JFK's knees about an inch away-if that- from the top of Connally's seat.
Connally was removed first. The jump seat lifted up so I expect that they would have lifted the seat up to remove JFK. In any event, we don't really know how JFK's feet were 25 ms after the head shot. But if you are basing your conclusion of a neuromuscular reaction causing the rear-left motion, it was not because his feet were pinned. I expect the movement of feet takes significantly longer than 25 ms.
The explosion of head matter exited from TOP of the head--not the "left side"-- but the top.
I corrected my post shortly afterward to "right side". You can see the opening up of the right side of his head and you can see a burst of matter over a hemispheric cloud from his head, generally to the right and forward. That creates an impulse (force x time) in the rear-left direction (ie. opposite to the direction of the matter in the cloud).
The left side of the skull was basically undamaged same as the brain-and only a fraction of the right top side of the skull was missing. Nearly the whole top of his head was gone, according to the top of the head autopsy photos. Not only can the top of JFK's head be seen flying through the air at a speed of around 80MPH (calculated by Dr. John Lattimer in his book) we can see the skull fragments in the Zapruder film in motion, and a large skull fragment can be seen in both Z 314 between JFK and the Connallys, but the same fragment is captured in later frames bouncing off the top rest of Nellie Connally's seat and tumbling towards the floor of the car.
There is one large fragment that goes up at about a 65 degree angle to the horizontal in the forward direction. It appears to travel about a metre in 25 ms which is 40 m/sec (89 mph), so Lattimer's estimate is about right. The rearward momentum from that is 42% of its total momentum (cos 65°=.42). If it weighed 100 grams, that piece alone would carry 4 kg m/sec of momentum. So the rear-leftward kick from that would be almost 1/3 of the bullet's incoming momentum. And that is just one piece of the skull.
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So long as one offers a plausible mechanism to explain the body's motion and so long as there is no evidence at all of a shot from the front right, that is all one needs. Introducing an uncertain mechanism to explain the body's motion is just giving fuel to the conspiracy fanatics.
I don't see how the feet being jammed under the front seat helps prove that there was a neuromuscular spasm. There is nothing to show that JFK did not put his feet there before the shot. There was not a lot of room between the seats. That would be especially so with Connally in front because he was quite tall and he would likely have pushed the seat back as far as it would go. Besides, wouldn't a push of the body upward from the feet push the feet down?
The recoil from the exploding head provides a mechanism based on the evidence of what we can actually observe (matter driven out of the head at high speed). The mechanism of a neuromuscular spasm due to catastrophic loss of brain matter from the right side (which controls the left side of the body) does not have sufficient basis in fact. It may be possible but we really can't say it occurred. We can, however, say based on what is observed in the zfilm, that the head received a left-rearward impulse from the matter exploding out of the front right side of his head.
The recoil from the exploding head provides a mechanism based on the evidence of what we can actually observe (matter driven out of the head at high speed).
I don't think you understand what the so-called "jet effect" entails.
Do you believe that the momentum of any matter traveling away from the head has an equal and opposite impulse on the head?
Do you believe that when the bullet fragments exit the head they have a recoil effect on the head?
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The recoil from the exploding head provides a mechanism based on the evidence of what we can actually observe (matter driven out of the head at high speed).
I don't think you understand what the so-called "jet effect" entails.
Do you believe that the momentum of any matter traveling away from the head has an equal and opposite impulse on the head?
First of all, it is not about belief. This is demonstrated, repeatable, measurable, physical science: Newton's laws of motion.
If matter experiences a change in motion, there must be a force acting on it for a period of time (Newton 1). That force multiplied by time integrated over the period of its duration is the impulse or change in momentum it experiences.(Newton 2).
But forces are always paired (Newton 3). So if matter changes its momentum by experiencing forces for a period of time, another body must experience an equal but opposite force for the same period of time and, therefore, an equal and opposite change in momentum.(Newton 3).
So it is not about matter travelling away from the head. It is about matter experiencing a change in motion. The matter ejected from the head experienced a change in its motion due to a force supplied by other matter in the head from which it was ejected. Therefore, that other matter-the remaining head - experienced an equal and opposite change in momentum.
Do you believe that when the bullet fragments exit the head they have a recoil effect on the head?
The laws of physics apply. If the bullet experiences a change of momentum while in contact with matter, that matter experiences an equal and opposite change in momentum. If the matter was the head, the head experiences a momentum change that is equal in magnitude and opposite in direction to the change in momentum of the bullet.
If the bullet experienced an increase in its forward momentum in passing through the head, which seems unlikely, but possible, it would impart some recoil momentum to the head. For example, if the bullet came to a stop in the head and then exploded out of the head due to the built-up pressure in the head and the skull opening up, this would occur.
If the bullet passed through the head and just slowed down, the change in momentum of the bullet is opposite to its direction of travel (ie. toward the shooter). So the head would experience a change in momentum that is equal and opposite to the change in bullet momentum (ie. forward, away from the shooter). In that case, the bullet fragments do not experience any increase in forward momentum on leaving the head so the head does not experience any increase in rearward momentum (recoil). This is, perhaps, the more likely of the two possible scenarios.
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First of all, it is not about belief. This is demonstrated, repeatable, measurable, physical science: Newton's laws of motion.
If matter experiences a change in motion, there must be a force acting on it for a period of time (Newton 1). That force multiplied by time integrated over the period of its duration is the impulse or change in momentum it experiences.(Newton 2).
But forces are always paired (Newton 3). So if matter changes its momentum by experiencing forces for a period of time, another body must experience an equal but opposite force for the same period of time and, therefore, an equal and opposite change in momentum.(Newton 3).
So it is not about matter travelling away from the head. It is about matter experiencing a change in motion. The matter ejected from the head experienced a change in its motion due to a force supplied by other matter in the head from which it was ejected. Therefore, that other matter-the remaining head - experienced an equal and opposite change in momentum.
The laws of physics apply. If the bullet experiences a change of momentum while in contact with matter, that matter experiences an equal and opposite change in momentum. If the matter was the head, the head experiences a momentum change that is equal in magnitude and opposite in direction to the change in momentum of the bullet.
If the bullet experienced an increase in its forward momentum in passing through the head, which seems unlikely, but possible, it would impart some recoil momentum to the head. For example, if the bullet came to a stop in the head and then exploded out of the head due to the built-up pressure in the head and the skull opening up, this would occur.
If the bullet passed through the head and just slowed down, the change in momentum of the bullet is opposite to its direction of travel (ie. toward the shooter). So the head would experience a change in momentum that is equal and opposite to the change in bullet momentum (ie. forward, away from the shooter). In that case, the bullet fragments do not experience any increase in forward momentum on leaving the head so the head does not experience any increase in rearward momentum (recoil). This is, perhaps, the more likely of the two possible scenarios.
The matter ejected from the head experienced a change in its motion due to a force supplied by other matter in the head from which it was ejected. Therefore, that other matter-the remaining head - experienced an equal and opposite change in momentum.
What was the "force supplied by other matter in the head"?
What force did the remaining head use to eject matter?
Where did this force come from?
Because it's not the bullet.
You are saying the remaining head provided a force that ejected the jet of material.
How was this force provided?
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The matter ejected from the head experienced a change in its motion due to a force supplied by other matter in the head from which it was ejected. Therefore, that other matter-the remaining head - experienced an equal and opposite change in momentum.
What was the "force supplied by other matter in the head"?
What force did the remaining head use to eject matter?
Where did this force come from?
Because it's not the bullet.
You are saying the remaining head provided a force that ejected the jet of material.
How was this force provided?
The force was provided by pressure that was built up inside the head by the bullet and suddenly released.
We know that there was pressure built up because the skull opened up and matter exploded out of the head in wide directions. We can see that in the zfilm.
As you know, the bullet passing through tissue creates a temporary cavity around it. But in a head, there is no ability to expand the volume. The brain, like water, is almost incompressible so a very small compression of volume increases the pressure tremendously. So the energy deposited in the head builds up pressure. When that pressure is released by the rupturing of the skull (likely initiated by the bullet exiting through the front of the head) matter is propelled out of the opening from the tremendous force (pressure x area).
If the pressure increase was just one atmosphere (1 bar or just over 100 kPa or 100,000 N/m^2) and the area of the skull that opened up was (estimating the size of the opening) was, say, 10 cm x 10 cm (4"x4") or .01 m^2, the total force on the matter expelled (force=Pressure x area) would have been 1000 N. if the matter expelled was 400 grams or .4 kg, then the acceleration would have been:
a=F/m=1000/.4= 2500 m/s2.
So in 10 ms. or 1/100th of a second, the speed would have been v=at=2500/100=25m/s That represents a momentum change of .4 x25 = 10 kg m/s and an equal and opposite momentum change to the head. Since the total incoming bullet momentum was .01g x 610 m/s =6.1 k m/s, the momentum of the recoiling head exceeds the maximum forward momentum imparted by the bullet. So head goes backward.
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I think it was a combination of elements that created the back and to the left motion.
Kennedy's back brace stopped him from falling forward.
(https://assets1.cbsnewsstatic.com/hub/i/r/2013/11/19/27243793-d84f-4aa7-b0f3-2af4222459ab/thumbnail/640x480/ef69636ca98dc3a5270f08d76dbda49e/kennedybrace.jpg)
(https://www.cbsnews.com/news/jfks-back-brace-may-have-cost-him-his-life-doctor-says/)
The jet effect drove him backwards.
(https://i.postimg.cc/Gh4cpkRv/jet-effect.gif)
And I also agree with Joe's thread opener that a penetrating bullet simply lacks the kinetic energy to throw anyone anywhere.
Mythbusters fired a 50 cal bullet into a steel plated dummy with no penetration and it barely moved.
Also in the following video, a firing squad shoots multiple men and they just drop down and virtually all of them fall back towards the shooters.
@ 0.37
JohnM
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I think it was a combination of elements that created the back and to the left motion.
Kennedy's back brace stopped him from falling forward.
(https://www.cbsnews.com/news/jfks-back-brace-may-have-cost-him-his-life-doctor-says/)
The jet effect drove him backwards.
(https://i.postimg.cc/Gh4cpkRv/jet-effect.gif)
Great clips of jet-effect. I will add Chad Zimmerman's turkey shoot:
(https://i.ibb.co/jRZmQZw/Chad-Zimmerman-Turkey-Shoot-Jeteffect.gif)
And I also agree with Joe's thread opener that a penetrating bullet simply lacks the kinetic energy to throw anyone anywhere.
Again it is not about insufficient kinetic energy. The bullet has more than enough kinetic energy to throw a body. A .01 kg bullet at 610 m/s has kinetic energy of .005 x (610)^2 Joules = 1860 Joules. A 100 kg body recoiling at 1 m/s has only 50 Joules of kinetic energy (mv^2/2) or only about 2.5% of the bullet energy.. What is lacking is the mechanism to convert bullet energy into motion of the body. Jet effect is a rather crude energy converter and uses a small fraction of the bullet kinetic energy. But the jet effect can impart significant momentum as your clips show - more than the incoming bullet if enough matter explodes from the body.
Suppose a 1800 Joule bullet could be "caught" by a mechanism that compresses a spring in a 100 kg body as the bullet slows down so that the kinetic energy of is all transferred to the spring. The release of that spring against a fixed wall, say, would cause the 100 kg body to be thrown at a speed of: v= √{2E/m}= √36=6 m/s
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Great clips of jet-effect. I will add Chad Zimmerman's turkey shoot:
(https://i.ibb.co/jRZmQZw/Chad-Zimmerman-Turkey-Shoot-Jeteffect.gif)
Again it is not about insufficient kinetic energy. The bullet has more than enough kinetic energy to throw a body. A .01 kg bullet at 610 m/s has kinetic energy of .005 x (610)^2 Joules = 1860 Joules. A 100 kg body recoiling at 1 m/s has only 50 Joules of kinetic energy (mv^2/2) or only about 2.5% of the bullet energy.. What is lacking is the mechanism to convert bullet energy into motion of the body. Jet effect is a rather crude energy converter and uses a small fraction of the bullet kinetic energy. But the jet effect can impart significant momentum as your clips show - more than the incoming bullet if enough matter explodes from the body.
Suppose a 1800 Joule bullet could be "caught" by a mechanism that compresses a spring in a 100 kg body as the bullet slows down so that the kinetic energy of is all transferred to the spring. The release of that spring against a fixed wall, say, would cause the 100 kg body to be thrown at a speed of: v= √{2E/m}= √36=6 m/s
The bullet has more than enough kinetic energy to throw a body.
Of course you are right, I should have said that the amount of movement would be limited to an inch or two, just like we see in the Zapruder film and the Mythbusters clip.
JohnM
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The force was provided by pressure that was built up inside the head by the bullet and suddenly released.
We know that there was pressure built up because the skull opened up and matter exploded out of the head in wide directions. We can see that in the zfilm.
As you know, the bullet passing through tissue creates a temporary cavity around it. But in a head, there is no ability to expand the volume. The brain, like water, is almost incompressible so a very small compression of volume increases the pressure tremendously. So the energy deposited in the head builds up pressure. When that pressure is released by the rupturing of the skull (likely initiated by the bullet exiting through the front of the head) matter is propelled out of the opening from the tremendous force (pressure x area).
If the pressure increase was just one atmosphere (1 bar or just over 100 kPa or 100,000 N/m^2) and the area of the skull that opened up was (estimating the size of the opening) was, say, 10 cm x 10 cm (4"x4") or .01 m^2, the total force on the matter expelled (force=Pressure x area) would have been 1000 N. if the matter expelled was 400 grams or .4 kg, then the acceleration would have been:
a=F/m=1000/.4= 2500 m/s2.
So in 10 ms. or 1/100th of a second, the speed would have been v=at=2500/100=25m/s That represents a momentum change of .4 x25 = 10 kg m/s and an equal and opposite momentum change to the head. Since the total incoming bullet momentum was .01g x 610 m/s =6.1 k m/s, the momentum of the recoiling head exceeds the maximum forward momentum imparted by the bullet. So head goes backward.
I'm not certain I agree with these calculations. But putting this aside, you say that after 10 ms, the head started to move backwards. If so, how is it, that according to the study by Physics Graduate Student William Hoffman, in his work for Josiah Thompson for the book "Six Seconds in Dallas" measured JFK's head at frame 313, two inches, or 5 cm, forward of the 312 position, by frame 313?
Why did the head immediately, or almost immediately (after just 10 ms) start moving backwards, and yet ended up 2 inches forward?
Provide me with a possible scenario. Don't use the excuse "Well, we can't tell exactly what happened". Just give us a possible scenario. That would be good enough.
We can use the following time system. z312.0 is when the shutter opens on frame 312. z312.5 is when the shutter closed on frame 312.
So, I need to see something like the following:
z312.5 - the bullet strikes.
during z312.5-z312.7, the head moves forward 2.5 inches, or 6.25 cm, at a rate of 12.5 mph.
z312.7 - the head explodes and the head starts moving backwards, at a rate of 0.6 inches per frame, or about 0.6 mph.
z313.5 - the head has moved back to a position where the head is 2.0 inches ahead of the position in frame 312.
This scenario is clearly impossible, for the bullet to push the head forward at 12.5 mph.
But what possible scenario, not a scenario you can 'prove', but a possible scenario, that would allow the head to start moving backwards after 10 ms, and still have the head 2 inches ahead of it's frame 312 position by the time the shutter closed at frame z313.
So, to summarize:
Questions:
Is there a possible scenario that fits the William Hoffman data?
Is this scenario in accordance with Classical Physics?
Is so, what is that scenario?
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Why did the head immediately, or almost immediately (after just 10 ms) start moving backwards, and yet ended up 2 inches forward?
The impulses to the head are not in opposite directions. And they do not start at the same time.
The impulse to the head from the bullet is opposite to the direction of the bullet's change in momentum ie the impulse to the head from the bullet is forward. The impulse to the head from the jet effect is opposite to the direction of the ejection of matter. The matter from the head explodes out of the right front upper part of his head. This pushes the head to the left side and down and to the rear.
The different directions of these impulses also affect the body differently. The sideways impulse takes the body with it whereas the forward impulse causes the head mainly to pivot forward.
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The impulses to the head are not in opposite directions. And they do not start at the same time.
The impulse to the head from the bullet is opposite to the direction of the bullet's change in momentum ie the impulse to the head from the bullet is forward. The impulse to the head from the jet effect is opposite to the direction of the ejection of matter. The matter from the head explodes out of the right front upper part of his head. This pushes the head to the left side and down and to the rear.
The different directions of these impulses also affect the body differently. The sideways impulse takes the body with it whereas the forward impulse causes the head mainly to pivot forward.
It is true, the ‘Jet Effect’ does not have to push the head straight back. With the side of the head exploding outwards, the ‘Jet Effect’ would push the head to the left. But what I am interested in the effect it would have on pushing the head to the rear. The ‘Jet Effect’ theory was developed to come up with a possible reason why the head started moving backwards.
Question: What was the change of speed, and the resulting speed of the head, rearward, as a result of the ‘Jet Effect’?
For instant, you could say:
+ The initial speed of the head forward was: 2.0 mph
+ When the head exploded, it added 2.5 mph motion to the rear
+ Resulting in a motion to the rear of 2.5 – 2.0 or 0.5 mph to the rear
Basically, I am interested in your estimate of the rearward component of the velocity vector.
For instant, the shot from Oswald’s position was coming down at an angle of ‘b’, 16 degrees, relative to the horizon.
It was moving at an angle of ‘a’, 3 degrees, to the left, relative to the limousine. On the horizontal plane, the shot came almost directly from behind.
So, the ‘x’ component of the velocity of the bullet, the ‘forward’ component, was cos (16) * cos (3) = 0.96 % of the scalar velocity. If the scalar velocity of the resulting head movement was 2.00 mph, the forward velocity was 1.92 mph. For all practicable purposes, this forward component of the velocity is the same as the scalar velocity.
The ‘y’ component of the velocity of the bullet, the ‘leftward’ component was, cos (16) * sin (3) = 0.05. If the scalar velocity of the resulting head movement was 2.00 mph, the leftward velocity was 0.05 mph, not significant.
The ‘z’ component of the velocity of the bullet, the ‘downward’ component was, sin (16) = 0.28. If the scalar velocity was the resulting head movement was 2.00 mph, the downward velocity would be 0.55 mph. If the head was able to move downward freely. Which it was not.
Question: Can you come up with a possible velocity (not a proven, but possible) of the head, rearward, immediately after the effect of the ‘Jet Effect’ takes place, that:
+ Takes place 10 ms after the bullet strikes.
+ That ends up with the head at frame 313 two inches ahead of the frame 312 position, as William Hoffman’s data indicates?
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It is true, the ‘Jet Effect’ does not have to push the head straight back. With the side of the head exploding outwards, the ‘Jet Effect’ would push the head to the left. But what I am interested in the effect it would have on pushing the head to the rear. The ‘Jet Effect’ theory was developed to come up with a possible reason why the head started moving backwards.
Question: What was the change of speed, and the resulting speed of the head, rearward, as a result of the ‘Jet Effect’?
For instant, you could say:
+ The initial speed of the head forward was: 2.0 mph
+ When the head exploded, it added 2.5 mph motion to the rear
+ Resulting in a motion to the rear of 2.5 – 2.0 or 0.5 mph to the rear
Basically, I am interested in your estimate of the rearward component of the velocity vector.
Do you mean rearward momentum of the head and body relative to the body or to the car? There is a difference because JFK was turned to the left and leaning to his left and forward. Also, the head was leaning forward more than the body. I don't see the head being driven back relative to the body. It was driven to the body left which was to the car rear-left and this caused the whole body to move rear-left.
This is going to be a rough estimate, but here goes:
The head and body pivot. The head pivots on the neck. The upper body, being seated, pivots from the seat. So we really need to find the angular speed imparted to the head by the bullet and the angular speed of the head and body from the jet effect. The angular speed (ω) of a body can be determined from the angular impulse or angular momentum (L) and moment of inertia (I) of the body by:
L=Iω. We are going to use the moment of inertia of a sphere for the head pivoting about the neck and the moment of inertia of a cylinder pivoting on the seat for the head/torso.
My estimates of the motion of the head due to the bullet imparting momentum due to its impact to the head:
1. JFK was turned 15 degrees to the left. He was leaning left at an angle of 10 degrees and his head was leaning forward 40 degrees. I will assume the head mass is 5 kg. which appears to be the average mass of a human head (google).
2. The bullet was travelling at a right to left angle of 5 degrees and a downward angle of arctan(60/275)=12 degrees relative to the horizontal. The car was on a downward 3 degree slope. So the downward angle relative to the car was 9 degrees.
3. The 10 gram bullet entered the head travelling 1900 fps or 580 m/s, passed through the head and exited at 360 fps or 110 m/s and did not change direction. So the change in momentum was .01 x 470 =4.7 kg m/s which imparted a forward momentum of 4.7 kg m/s to the head at an angle of 5 degrees right to left and 9 degrees down.
4. The bullet struck above the centre of mass of the head. I would put the centre of mass of the head halfway between the ears, so the bullet path was about and inch or 2.5 cm above the centre of mass.
5. The bullet struck JFK just before z313 was exposed but after the end of exposure of z312. There is 30 ms. between frames where film is not being exposed. I will assume that it struck 30 ms. before the exposure of z313 began.
6. So 4.7 kg m/s impulse to the 5 kg head would result in a 5 degree right to left and 9 degree downward velocity of just under 1 m/s: 940 mm/s or .94 mm/ms. So in the 30 ms before exposure of z313 began, the centre of mass of the head would have moved 30x.94= 28 mm or just over an inch in a direction 5 degrees to the right and 9 degrees down, assuming it was free to pivot from the neck.
7. Average speed through the head would have been (580+110)/2=345 m/s. Assuming a path of 20 cm or .2 m, the transit time through the head, assuming uniform stopping force was applied to the head would have been t=d/v=.2/345=.0006 s = .6 ms. So we don't really have to take into account the fact that this impulse took some time to impart momentum.
8. Since the head pivots from the neck and since the bullet struck above the centre of mass, one has to determine the angular impulse to the head. The head centre of mass (middle of the ear to base of the neck) is about 17 cm above the neck, so the angular impulse is r x p=.17 x 4.7= .8 kg m^2/sec which is the angular momentum of the head. To determine the angular speed, we divide by the moment of inertia of the head. Assuming it to be approximately a 5 kg sphere of radius 10 cm rotating about a pivot 17 cm. from the centre of mass, the moment of inertia is .02 + 5x(.17)^2=.16 kg m^2. So the angular speed would be .8/.16=5 radians/sec or about 280 degrees per second or .28 degrees per millisecond. In the space of 30 ms (the time between end of frame 312 and beginning of frame 313) the head would pivot 9 degrees forward.
9. There is a limit to how far forward the head can move because the chin cannot go past the chest.
Here are my estimates of the motion of the head and body due to the jet-effect:
1. The jet effect did not begin until the bullet exited the head. At that point there was no longer any forward momentum being transferred to the head from the bullet.
2. Frame z313 appears to show a streak from the motion of a piece of matter, possibly a skull fragment moving at an upward angle of about 65 degrees above car horizontal. It appears to be about 1 metre long and it starts about a metre from the head. This gives us information not only about the speed of the ejected matter but also the timing of when it started. Since the exposure is 25 ms duration, 1 m of travel in 25 ms is 40 m/s. Since it had already travelled 1 m before z313 began to be exposed, this means that the head erupted about 25 ms. before z313 was exposed or about 5 ms. after the end of exposure of z312. Since z312 does not provide any indication of the head being hit, this suggests that the bullet hit less than 5 ms after the exposure of z312 ended.
3. There appears to be a substantial amount of brain, skull bone and blood erupting from the head wound. Doctors reported that a substantial portion of the brain was missing. If the mass of matter exploding from the head was only 300 g, travelling initially at 40 m/s, the total momentum would be 12 kg m/s or almost 3 times the momentum of the incoming bullet. But it does not all explode in the same direction. It forms what appears to be a hemispheric cloud around the exit wound. So the average would be about cos 45 x total momentum = 70% of 12 kg m/s = 8.4 kg m/s/
4. So the head and the body to which it is attached would, under those assumptions, recoil to the body left with 8.4 kg m/s of momentum. Unlike the forward momentum imparted by the bullet, however, there is nothing really to stop the upper body from moving to the left so it keeps going.
5. If the torso received an impulse of 8.4 kg m/s applied to the right side of the upper skull, which would be a distance of approximately 90 cm above the seat or pivot point of the torso, the angular impulse, r x p would be .9 x 8.4 kg m^2/s = 7.5 kg m^2/s.
[Correction: I was using the wrong axis of rotation for the torso. The moment of inertia of a cylinder of length Len, mass M and radius R about an axis at one end is: MR^2/4 + M(Len)^2/3. If the centre of mass of the torso is midway, 45 cm above the seat (Len=.9), and the torso is approximately a solid cylinder of mass=40 kg and radius 20 cm (moment of inertia, I = MR^2/4+M(Len)^2/3= 40x(.2)^2/4+40x(.9)^2/3=.4+10.8=11.2 kg m^2/s). So the angular speed of the torso would be: L/I=7.5/11.2=.7 radians/sec or 40 degrees/second In 55 ms or one frame, it would rotate a bit more than 2 degrees to the body left.
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Do you mean rearward momentum of the head and body relative to the body or to the car? There is a difference because JFK was turned to the left and leaning to his left and forward. Also, the head was leaning forward more than the body. I don't see the head being driven back relative to the body. It was driven to the body left which was to the car rear-left and this caused the whole body to move rear-left.
This is going to be a rough estimate, but here goes:
The head and body pivot. The head pivots on the neck. The upper body, being seated, pivots from the seat. So we really need to find the angular speed imparted to the head by the bullet and the angular speed of the head and body from the jet effect. The angular speed (ω) of a body can be determined from the angular impulse or angular momentum (L) and moment of inertia (I) of the body by:
L=Iω. We are going to use the moment of inertia of a sphere for the head pivoting about the neck and the moment of inertia of a cylinder pivoting on the seat for the head/torso.
My estimates of the motion of the head due to the bullet imparting momentum due to its impact to the head:
1. JFK was turned 15 degrees to the left. He was leaning left at an angle of 10 degrees and his head was leaning forward 40 degrees. I will assume the head mass is 5 kg. which appears to be the average mass of a human head (google).
2. The bullet was travelling at a right to left angle of 5 degrees and a downward angle of arctan(60/275)=12 degrees relative to the horizontal. The car was on a downward 3 degree slope. So the downward angle relative to the car was 9 degrees.
3. The 10 gram bullet entered the head travelling 1900 fps or 580 m/s, passed through the head and exited at 360 fps or 110 m/s and did not change direction. So the change in momentum was .01 x 470 =4.7 kg m/s which imparted a forward momentum of 4.7 kg m/s to the head at an angle of 5 degrees right to left and 9 degrees down.
4. The bullet struck above the centre of mass of the head. I would put the centre of mass of the head halfway between the ears, so the bullet path was about and inch or 2.5 cm above the centre of mass.
5. The bullet struck JFK just before z313 was exposed but after the end of exposure of z312. There is 30 ms. between frames where film is not being exposed. I will assume that it struck 30 ms. before the exposure of z313 began.
6. So 4.7 kg m/s impulse to the 5 kg head would result in a 5 degree right to left and 9 degree downward velocity of just under 1 m/s: 940 mm/s or .94 mm/ms. So in the 30 ms before exposure of z313 began, the centre of mass of the head would have moved 30x.94= 28 mm or just over an inch in a direction 5 degrees to the right and 9 degrees down, assuming it was free to pivot from the neck.
7. Average speed through the head would have been (580+110)/2=345 m/s. Assuming a path of 20 cm or .2 m, the transit time through the head, assuming uniform stopping force was applied to the head would have been t=d/v=.2/345=.0006 s = .6 ms. So we don't really have to take into account the fact that this impulse took some time to impart momentum.
8. Since the head pivots from the neck and since the bullet struck above the centre of mass, one has to determine the angular impulse to the head. The head centre of mass (middle of the ear to base of the neck) is about 17 cm above the neck, so the angular impulse is r x p=.17 x 4.7= .8 kg m^2/sec which is the angular momentum of the head. To determine the angular speed, we divide by the moment of inertia of the head. Assuming it to be approximately a 5 kg sphere of radius 10 cm rotating about a pivot 17 cm. from the centre of mass, the moment of inertia is .02 + 5x(.17)^2=.16 kg m^2. So the angular speed would be .8/.16=5 radians/sec or about 280 degrees per second or .28 degrees per millisecond. In the space of 30 ms (the time between end of frame 312 and beginning of frame 313) the head would pivot 9 degrees forward.
9. There is a limit to how far forward the head can move because the chin cannot go past the chest.
Here are my estimates of the motion of the head and body due to the jet-effect:
1. The jet effect did not begin until the bullet exited the head. At that point there was no longer any forward momentum being transferred to the head from the bullet.
2. Frame z313 appears to show a streak from the motion of a piece of matter, possibly a skull fragment moving at an upward angle of about 65 degrees above car horizontal. It appears to be about 1 metre long and it starts about a metre from the head. This gives us information not only about the speed of the ejected matter but also the timing of when it started. Since the exposure is 25 ms duration, 1 m of travel in 25 ms is 40 m/s. Since it had already travelled 1 m before z313 began to be exposed, this means that the head erupted about 25 ms. before z313 was exposed or about 5 ms. after the end of exposure of z312. Since z312 does not provide any indication of the head being hit, this suggests that the bullet hit less than 5 ms after the exposure of z312 ended.
3. There appears to be a substantial amount of brain, skull bone and blood erupting from the head wound. Doctors reported that a substantial portion of the brain was missing. If the mass of matter exploding from the head was only 300 g, travelling initially at 40 m/s, the total momentum would be 12 kg m/s or almost 3 times the momentum of the incoming bullet. But it does not all explode in the same direction. It forms what appears to be a hemispheric cloud around the exit wound. So the average would be about cos 45 x total momentum = 70% of 12 kg m/s = 8.4 kg m/s/
4. So the head and the body to which it is attached would, under those assumptions, recoil to the body left with 8.4 kg m/s of momentum. Unlike the forward momentum imparted by the bullet, however, there is nothing really to stop the upper body from moving to the left so it keeps going.
5. If the torso received an impulse of 8.4 kg m/s applied to the right side of the upper skull, which would be a distance of approximately 90 cm above the seat or pivot point of the torso, the angular impulse, r x p would be .9 x 8.4 kg m^2/s = 7.5 kg m^2/s. If the centre of mass of the torso is midway, 45 cm above the seat, and the torso is approximately a solid cylinder of mass=40 kg and radius 20 cm (moment of inertia = MR^2/2= 40x(.2)^2/2=.8 kg m^2/s), the angular speed would be angular momentum/moment of inertia = L/I=7.5/.8=9.3 radians/sec or 530 degrees/second or .53 deg/ms. In 55 ms or one frame, it would rotate about 25 degrees to the body left.
We are in agreement on a lot of issues.
The bullet struck at about the time the shutter closed on z312.
I believe the common belief among LNers, that the 'Jet Effect' caused JFK's head to move backwards is false. Because the head moved forward by two inches between frames 312 and 313.
The expected momentum the head should receive from a WCC/MC bullet fired from behind is 2 mph, or 2 inches per Zapruder frame.
The two inches of forward movement means:
a. The bullet struck around z312.5, just as the shutter closed. Because we need a full Zapruder frame, 55 ms, for the head to reach two inches forward by the time the shutter closes at z313.5.
b. The is no strong 'Jet Effect' pushing the head back, because the head would not have reached anything close to two inches ahead of the z312 position, with a full 45 ms of time for this alleged momentum change to affect the movement of the head.
The one disagreement is that you seem to claim the 'Jet Effect' definitely pushed JFK's head to the left.
I say, this may be true. Or might not be true. It may be the head was pushed strongly to the left. As you pointed out, a 'Jet effect' does not have to be related to the original direction of the bullet. It mainly has to do with the direction organic material erupted towards, which may be in almost any direction. If there was a strong 'Jet effect' push to the left, it is hard to see, but it would be hard to see, because Zapruder was filming from the side so we can easily see and measure movement that is forward, or backward, or upward, or downward, but not to the left or the right.
But is equally possible, in my view, that the 'Jet Effect', while it did push the head in some direction, might not have pushed the head very much. Unlike taped melons. Possibly because too much energy is used to break apart a human skull and the is not enough energy left over to propel organic material at a high enough velocity to affect the movement of the head very much.
Without a film view from a different direction, like from behind, like from David Powers position, we will never know if there was an immediate move of the head to the left, in the next frame after the bullet struck.
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We are in agreement on a lot of issues.
The bullet struck at about the time the shutter closed on z312.
I believe the common belief among LNers, that the 'Jet Effect' caused JFK's head to move backwards is false. Because the head moved forward by two inches between frames 312 and 313.
The expected momentum the head should receive from a WCC/MC bullet fired from behind is 2 mph, or 2 inches per Zapruder frame.
The bullet, although moving right to left relative to the car by about 5 degrees, passed from the middle of the back of he skull to the right side of the head. This means that JFK was turned to the left so that his head was 30 degrees to the car direction. A leftward impulse from the explosive ejection of matter from the head will move the head to the car left and car rear. That is exactly what we see.
Also, please note that I corrected my calculation of the movement of the body. I did this late yesterday and as I was looking at it this morning I immediately saw that my figure of 25 degrees in one frame for the body made no sense. I quickly realized that I used the moment of inertia of a cylinder (torso) about its long axis when I should have used the moment about an axis at its end.
The moment of inertia of a cylinder of length Len, mass M and radius R about an axis at one end is: MR^2/4 + M(Len)^2/3. If the centre of mass of the torso is midway, 45 cm above the seat (Len=.9), and the torso is approximately a solid cylinder of mass=40 kg and radius 20 cm (moment of inertia, I = MR^2/4+M(Len)^2/3= 40x(.2)^2/4+40x(.9)^2/3=.4+10.8=11.2 kg m^2/s). So the angular speed of the torso would be: L/I=7.5/11.2=.7 radians/sec or 40 degrees/second In 55 ms or one frame, it would rotate a bit more than 2 degrees to the body left, which is about 1/4 of the rate of rotation of the head from the incoming bullet. This is a left and rearward rotation of the body including head, so there will not be much change in the position of the head for several frames.
The two inches of forward movement means:
a. The bullet struck around z312.5, just as the shutter closed. Because we need a full Zapruder frame, 55 ms, for the head to reach two inches forward by the time the shutter closes at z313.5.
b. The is no strong 'Jet Effect' pushing the head back, because the head would not have reached anything close to two inches ahead of the z312 position, with a full 45 ms of time for this alleged momentum change to affect the movement of the head.
The one disagreement is that you seem to claim the 'Jet Effect' definitely pushed JFK's head to the left.
You cannot ignore the different directions of the forces. We can see that a huge flap of skull on the right temple opens up but the forehead remains intact.
I say, this may be true. Or might not be true. It may be the head was pushed strongly to the left. As you pointed out, a 'Jet effect' does not have to be related to the original direction of the bullet. It mainly has to do with the direction organic material erupted towards, which may be in almost any direction. If there was a strong 'Jet effect' push to the left, it is hard to see, but it would be hard to see, because Zapruder was filming from the side so we can easily see and measure movement that is forward, or backward, or upward, or downward, but not to the left or the right.
But is equally possible, in my view, that the 'Jet Effect', while it did push the head in some direction, might not have pushed the head very much. Unlike taped melons. Possibly because too much energy is used to break apart a human skull and the is not enough energy left over to propel organic material at a high enough velocity to affect the movement of the head very much.
Energy is used when work is done. Work is Force x distance. Breaking a skull requires a huge force but it is not applied over much distance - a few molecular diameters to break molecular bonds. The work required to break apart a skull is also made easier after the bullet has already penetrated the skull and caused fractures. Ejection of 400 grams of matter at 40 m/s only requires .4x(40^2)/2=320 Joules or only about 1/6th of the total bullet energy.
Without a film view from a different direction, like from behind, like from David Powers position, we will never know if there was an immediate move of the head to the left, in the next frame after the bullet struck.
Because the body-leftward rotation of the body is only 2 degrees/frame where as the car-forward rotation of the head would be 9 degrees/frame, one does not see an immediately reversal of the head movement despite the greater impulse from the head explosion. The different directions have a completely different effect upon the motion of the body.
We know that jet effect occurs because of the explosive nature of the exit wound. The only disagreement should be over its magnitude and direction and its effect on the body, not whether it occurred.
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. . .
We know that jet effect occurs because of the explosive nature of the exit wound. The only disagreement should be over its magnitude and direction and its effect on the body, not whether it occurred.
Agreed. The Jet Effect is real. The Jet Effect did occur. But I suspect it was of weak magnitude. It did not seem to effect the motion of JFK's head, either forward or backwards, a significant amount.
But it is possible the Jet Effect was stronger than I suspect. If the jet of material just happened to erupted to JFK's right, it would push the head to the left. This would be hard to measure in the Zapruder film, since that motion would be directly away from the camera.
When I state the 'Jet Effect' is a false explanation, the 'Neurological Spasm' is the true explanation of JFK's backwards motion, I am only referring to the effect on the backwards motion, which leads many people to think the shot had to have come from the front. The Jet Effect clearly had minimum effect on the backwards motion. The effect of the Jet Effect on motion to the left is unknown, since it cannot be easily measured. Although Dale Myers may have some information on that.
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The “neuromuscular spasm” isn’t a great explanation either, but it’s all they have in order to preserve the narrative.
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The “neuromuscular spasm” isn’t a great explanation either, but it’s all they have in order to preserve the narrative.
It is a very good explanation. Because it is the only explanation that explains JFK's head continuous acceleration backwards from z313 through z317. The only other explanation, which no one believes, is that there was a series of bullets during z313 through z317, each striking the head in at least 4 consecutive frames, striking at the same rate the Zapruder film was made, one bullet every 55 milliseconds. Plus another bullet fired from under the street, through the asphalt, through the bottom of the limousine and into JFK's right elbow.
The "neurological spasm" or the "neuromuscular spasm" is also a good theory because it has been demonstrated with animals. It has not been demonstrated with humans. It cannot be demonstrated with humans. Not because it has been tried and tried again and shown that it just doesn't happen. It's because this experiment is forbidden, even for condemned criminals because it is an afront to human dignity. Even film of murders, which I understand seem to show a neurological spam in humans, like the murder of a reporter in Nicaragua in 1979 cannot be shown as an afront to human dignity.
Any explanation that can be shown to occur in animals, and is the only plausible explanation, is a good explanation, except to the hopelessly biased.
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Agreed. The Jet Effect is real. The Jet Effect did occur. But I suspect it was of weak magnitude. It did not seem to effect the motion of JFK's head, either forward or backwards, a significant amount.
But it is possible the Jet Effect was stronger than I suspect. If the jet of material just happened to erupted to JFK's right, it would push the head to the left. This would be hard to measure in the Zapruder film, since that motion would be directly away from the camera.
When I state the 'Jet Effect' is a false explanation, the 'Neurological Spasm' is the true explanation of JFK's backwards motion, I am only referring to the effect on the backwards motion, which leads many people to think the shot had to have come from the front. The Jet Effect clearly had minimum effect on the backwards motion. The effect of the Jet Effect on motion to the left is unknown, since it cannot be easily measured. Although Dale Myers may have some information on that.
Remember, the impulse from the head is to the direction of JFK's left which is not the car left since JFK is turned about 30 degrees. So JFK's left is about 30 degrees to the rear. [Note: If the head was as wide as it is long, a bullet entering the middle of the back of the head and exiting on the front right corner of the head would be 30 degrees to the direction the head is facing. Since the head is not that wide, I suggest the angle through the head was a bit less - say 25 degrees. But the bullet was already travelling 5 degrees right to left relative to the car, so that 25 degrees through the head was on top of a 5 degree angle to the car, meaning JFK's head was pointing about 30 degrees to the left of the car direction.]
With JFK turned 30 degrees to the left, an impulse of magnitude p to JFK's left will consist of a rearward impulse of .5p and a car left impulse of .867p (sin(30)= 1/2 and cos(30)=.866). That is consistent with what we see in frames z315-320.
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It is a very good explanation. Because it is the only explanation that explains JFK's head continuous acceleration backwards from z313 through z317. The only other explanation, which no one believes, is that there was a series of bullets during z313 through z317, each striking the head in at least 4 consecutive frames, striking at the same rate the Zapruder film was made, one bullet every 55 milliseconds. Plus another bullet fired from under the street, through the asphalt, through the bottom of the limousine and into JFK's right elbow.
The "neurological spasm" or the "neuromuscular spasm" is also a good theory because it has been demonstrated with animals. It has not been demonstrated with humans. It cannot be demonstrated with humans. Not because it has been tried and tried again and shown that it just doesn't happen. It's because this experiment is forbidden, even for condemned criminals because it is an afront to human dignity. Even film of murders, which I understand seem to show a neurological spam in humans, like the murder of a reporter in Nicaragua in 1979 cannot be shown as an afront to human dignity.
Any explanation that can be shown to occur in animals, and is the only plausible explanation, is a good explanation, except to the hopelessly biased.
Where has it been demonstrated in animals?
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Where has it been demonstrated in animals?
"The Army film taken in 1948 of the goat shooting episodes convincingly explained the rearward reaction of the president's head as seen in the Zapruder film and very convincingly demonstrates that it could not have been caused by the frontal impact of a bullet, and equally convincingly demonstrates that it was caused by the convulsion of upper dorsal musculature receiving false signals from an exploding brain."
https://www.archives.gov/research/jfk/select-committee-report/part-4.html
Charles Petty, from the HSCA.
JohnM
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The goat reaction looks nothing like the JFK reaction.
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"The Army film taken in 1948 of the goat shooting episodes convincingly explained the rearward reaction of the president's head as seen in the Zapruder film and very convincingly demonstrates that it could not have been caused by the frontal impact of a bullet, and equally convincingly demonstrates that it was caused by the convulsion of upper dorsal musculature receiving false signals from an exploding brain."
https://www.archives.gov/research/jfk/select-committee-report/part-4.html
Charles Petty, from the HSCA.
That was a statement of the HSCA committee. Petty does not refer to the sheep film. Has anyone actually seen the film and, if so, can someone provide a link?
I note that Petty made two serious errors, in my view (none of which relate the motion of JFK after the head shot).
First of all, to the question posed by Mr. Bugliosi at 4:15 about a 1 second delay of Connally after being struck in the back, Petty suggests that can occur because people react differently and people sometimes don't even know they have been struck. Obviously, that does not fit Connally's evidence, which was that he felt the impact and that that forceful impact like a punch to the back occurred after he had heard the first shot, recognized it as a rifle shot and, fearing an assassination attempt, had turned around to check on JFK.
The second error, at 5:50 where he says that the bullet never penetrated the rib bone or the radius bone. I am not sure how he concludes that it did not penetrate the rib. While it "circled around the outside of the chest" (4:00) initially, it blasted through the last 10 cm of rib. The bullet also caused a comminuted fracture of the radius. While I agree that this does not require penetrating the wrist if it merely deflected on impact, the SBT says that it penetrated the radius in order to enter the left thigh.