What physics reveals about the JFK event

[Bill Chapman]

The jet effect IS all about conservation of momentum.  There was a spray of matter going forward out of the front right side of JFK's head.  The momentum of that matter could easily amount to several times the momentum of the incoming bullet, sending the head and body backward and to the left, overcoming and overwhelming the forward momentum imparted by the incoming bullet.  See: Alvarez's paper at 434:

• 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 tissue 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.

The exita fired upward at a steep vertical angle according to the film and subsequent tests
From what I've read and recall, without revisiting that information at this moment, Kennedy's feet where jammed tightly under the jump seat in front of him to the extent that it was very difficult to get him out of the car. This indicates a powerful neurological reaction according to the article.

'For every reaction there is an equal and opposite reaction' goes Newton's third law of momentum. Kennedy's head moves about 2.5" forward at the moment of impact, which roughly equals the recoil of a Carcano I've seen online.

[Michael O'Brian]

The exita fired upward at a steep vertical angle according to the film and subsequent tests
From what I've read and recall, without revisiting that information at this moment, Kennedy's feet where jammed tightly under the jump seat in front of him to the extent that it was very difficult to get him out of the car. This indicates a powerful neurological reaction according to the article.

'For every reaction there is an equal and opposite reaction' goes Newton's third law of momentum. Kennedy's head moves about 2.5" forward at the moment of impact, which roughly equals the recoil of a Carcano I've seen online.

Goway outta that ya dopey fool

[Andrew Mason]

The exita fired upward at a steep vertical angle according to the film and subsequent tests

While there is a piece that appears to go up at sharp angle, there is a much larger volume of ejected matter/blood right in front of the head.  There was matter spewed forward onto the Connallys and even onto the hood.  The direction was forward from the head.  The right side of his head was open and he was already leaning forward and to the left.  Matter ejected in a generally forward direction from the right side of his head would have pushed his head back and to the left.

From what I've read and recall, without revisiting that information at this moment, Kennedy's feet where jammed tightly under the jump seat in front of him to the extent that it was very difficult to get him out of the car. This indicates a powerful neurological reaction according to the article.

'For every reaction there is an equal and opposite reaction' goes Newton's third law of momentum. Kennedy's head moves about 2.5" forward at the moment of impact, which roughly equals the recoil of a Carcano I've seen online.

JFK's position in the car at Parkland would have been the result of everything that happened in the 5 minutes after the fatal shot.  Jackie leaned over and was on top of him during that time (she was not visible in a photograph taken when the car passed the Trade Mart). If you look at films of people being executed by a bullet to the head, they seem to just fall forward limply with no visible sign of neuromuscular spasm.  I am not saying it was not possible I am just saying that there would definitely have been jet effect pushing JFK's head to the back and to the left.  Whether there was anything additional is a matter of speculation. 

[Bill Chapman]

While there is a piece that appears to go up at sharp angle, there is a much larger volume of ejected matter/blood right in front of the head.  There was matter spewed forward onto the Connallys and even onto the hood.  The direction was forward from the head.  The right side of his head was open and he was already leaning forward and to the left.  Matter ejected in a generally forward direction from the right side of his head would have pushed his head back and to the left.JFK's position in the car at Parkland would have been the result of everything that happened in the 5 minutes after the fatal shot.  Jackie leaned over and was on top of him during that time (she was not visible in a photograph taken when the car passed the Trade Mart). If you look at films of people being executed by a bullet to the head, they seem to just fall forward limply with no visible sign of neuromuscular spasm.  I am not saying it was not possible I am just saying that there would definitely have been jet effect pushing JFK's head to the back and to the left.  Whether there was anything additional is a matter of speculation.

I suppose it has been calculated just how much jet-effect force would be required to cause Kennedy's movements backwards. Do you know if it has been shown that the explosive force reached a required standard?

[Jerry Freeman]

Witnesses reported that the final shot sounded like pa-pow. Possibility/probability...Kennedy was hit from behind as well as front right simultaneously. An autopsy revealing such events was scuttled courtesy of Lyndon Johnson.
https://www.wnd.com/2014/09/did-3-shooters-gun-down-jfk/

[Andrew Mason]

I suppose it has been calculated just how much jet-effect force would be required to cause Kennedy's movements backwards. Do you know if it has been shown that the explosive force reached a required standard?

The calculation is not difficult.  It all depends on how much mass is expelled from the head and what portion of the bullet energy it carries. 

The momentum is: p = square root of {2m(KE)} where m is the mass of the ejected matter and KE is the kinetic energy of that matter. 

Let's say the mass of ejected blood and brain matter was, conservatively, 100 g.  It was likely more.

The energy of that expelled mass can only make up a small fraction of the energy of the incoming bullet. This is because much of the bullet energy is used in deforming the bullet when penetrating the skull.  The energy of the deformed bullet plowing through the brain is converted into compression energy (pressure x volume of matter) of the brain material that is then converted to kinetic energy of the pressurized brain matter when the front of the skull ruptures. 

Conservatively, let's say only 10% of the bullet energy is converted into kinetic energy of the expelled brain matter.  A 10 g bullet moving at 1900 fps (580m/sec) carries kinetic energy (mv^2/2) of 1680 Joules.  This would mean that the 100 g. of ejected matter carried 168 J. of kinetic energy.  Using the formula for momentum, that means that the momentum imparted to the ejected matter was  p = sqrt{2 x .1 x 168) or about 6 kg m/sec of momentum.   This would propel the head (having a mass of, say, 13 lb or 6 kg)  back at a speed of about 1 m/sec.   

[Note: Another factor is gravity.  Once JFK's body was pushed far enough left, gravity would take effect.]

So even using these conservative estimates for the amount of matter ejected and its energy, there would be a significant momentum imparted to the head - enough to cause a visible rearward and leftward motion of the head.

[Bill Chapman]

Jackie Kennedy: "Top, behind the forehead"