Would A Bullet Really Knock You Backwards? DEBUNKED

[Mitch Todd]

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.

[Joe Elliott]

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.

[Mitch Todd]

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:



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.

[Joe Elliott]

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:



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.

[Andrew Mason]

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.

[Dan O'meara]

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, 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:


The original video is here:

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.

[Dan O'meara]

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;



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.



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.