What physics reveals about the JFK event

[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"

[Andrew Mason]

Note: Detached skull fragments were drawn at a larger scale than the head.

I'm wondering if the bullet entered at the back of the skull and created a few linear fractures radiating from the impact point, that ran into the lower rear of the skull.

Some of the surface of the skull at the point of impact was pushed forward such that it jutted forward of the intact skull above (see lateral X-ray):



The bullet fragmented into multiple pieces at the entry point and may not have had enough energy to fracture the intact skull opposite the entry. Possibly it was the bullet pressure wave that caused the fragmentation of skull above the right ear, or the gaping wound.

It is hard to say exactly what happened but I expect that the copper jacket ruptured on impact and much of the lead in the front part of the bullet melted and became a lead spray.  The copper jacket and a bit of still solid lead at the base is probably what passed through the skull. 

As an aside, it would have been nice if the ballistics experts actually weighed the copper jacket part and lead part of the bullet fragments separately to determine how much copper was recovered from the fragments.  We could then determine with a bit better detail what likely happened.  It would also help determine whether the fragments were from only 1 or 2 bullets.  If the amount of copper recovered exceeded the amount of copper of a single bullet we would know that more than one bullet struck in the car.

Nalli writes:

    "It is noted that the massive “defect” was not the “exit wound”
     of the bullet (as is commonly misunderstood), but rather
     corresponded roughly to the area where the maximum
     explosive energy was deposited by the bullet during its passage "

    "Here the large wound inflicted on the President's head was not a
     bullet exit wound, but rather the region of maximum temporary
     cavitation associated with KE transfer. This KE deposit
     propagated radially outward in the form of an expanding pressure
     wave resulting in a rupture and explosion of the skull."
 
    "However, all this said, note well that because such explosions are
     not necessarily the bullet outshoots, the momentum directly carried
     forward by a given bullet during passage may not be the primary
     player in a recoil effect."

The HSCA drawing seems to imply the right-side gaping wound was caused by the path of a bullet, or more precisely, one of its fragments, that impacted the inside of the skull to fracture it.

The size of the exit wound and the ruptured skull was definitely caused by the explosive exit wound.  However, there had to have been a significant piece of the missile to compress the brain matter that exploded out of the front part of the skull. Whether the skull ruptured because of the pressure alone before the bullet struck the skull from the inside or whether it occurred with the exit of that fragment through the skull is probably not possible to determine.

[Andrew Mason]

How about this? 

• Bullet enters skull at rear, disintegrates by time it gets through the bone

What do you mean by disintegrate? The bullet will compress and the jacket will rupture and molten lead will spray out.
   

• Bullet hole at rear of skull, with a few fractures radiating downwards

If a bullet will just make a bullet sized hole in glass, why would it radiate cracks on the entrance to a skull?

[Matt Grantham]

 Ah yes the single frame of forward motion somehow takes precedence over the end result of the motion Lots of drawing from the review board folks and we all know how different those descriptions are than Parkland and Bethesda

 Where are all the nutters who believe that force in physics causes and equal and opposite reaction and like to show sheep falling towards the direction of the shot. They would of course say the initial forward motion is indicative of a shot from the front Such consistency from you folks