What physics reveals about the JFK event

[Andrew Mason]

Nope a car crash is a perfect example of how kinetic energy/force is transferred into damage to the vehicle and momentum is lost

Nope. Kinetic energy is transferred into damage to the vehicle but momentum cannot be lost.  Momentum is always conserved. Conservation of momentum is among the most fundamental laws of physics.  A car crash is an example of an inelastic collision where kinetic energy is lost due to the damage (but not momentum).  A collision of two billiard balls is an example of an (almost) elastic collision where kinetic energy is retained as is momentum.   Momentum is NEVER lost in any kind of collision. See: http://hyperphysics.phy-astr.gsu.edu/hbase/elacol.html

[Matt Grantham]

Nope. Kinetic energy is transferred into damage to the vehicle but momentum cannot be lost.  Momentum is always conserved. Conservation of momentum is among the most fundamental laws of physics.  A car crash is an example of an inelastic collision where kinetic energy is lost due to the damage (but not momentum).  A collision of two billiard balls is an example of an (almost) elastic collision where kinetic energy is retained as is momentum.   Momentum is NEVER lost in any kind of collision. See: http://hyperphysics.phy-astr.gsu.edu/hbase/elacol.html

 Likely there is a linguistic misunderstanding of some sort here but when a car hits a wall damage occurs and momentum is lost. Or momentum is transferred into the structures that are transformed into damage if you prefer

[Andrew Mason]

Likely there is a linguistic misunderstanding of some sort here but when a car hits a wall damage occurs and momentum is lost. Or momentum is transferred into the structures that are transformed into damage if you prefer

The wall is attached to the earth.  Although it is not perceptible due to enormous mass of the earth, the earth's momentum increases.  The total momentum of the car + wall/earth are the same before and after the collision.  Kinetic energy is generally not conserved in collisions but momentum is always conserved.  Momentum cannot disappear.  It does not matter how or how much energy disappears as heat in the collision. In fact, if it is a collision where one body collides with another and the two bodies end up being stuck together, we can use the conservation of momentum to determine the final speed of the bodies and, thereby, determine exactly how much kinetic energy was lost in the collision.

The bottom line: If the bullet strikes the head and matter is ejected from the head, that ejected matter carries momentum and the remaining part of the head must gain an opposite amount of momentum such that the total momenta of the head matter and bullet are the same before, during, and after the impact.

[Matt Grantham]

  Matt said

                          In such a situation we can conclude the force of the bullet has been absorbed,


   There is no mention of momentum in this statement. So lets talk in terms of kinetic energy and force unless there is a problem with that?

[Andrew Mason]

  Matt said

                          In such a situation we can conclude the force of the bullet has been absorbed,


   There is no mention of momentum in this statement. So lets talk in terms of kinetic energy and force unless there is a problem with that?

If you want to discuss physics you have to use terms that have clear physical meaning.  While force and kinetic energy are well understood terms (F = ma; KE = mv^2/2), the concept of "absorbing a force" is not at all clear. You will have to explain what that means.

[Matt Grantham]

If you want to discuss physics you have to use terms that have clear physical meaning.  While force and kinetic energy are well understood terms (F = ma; KE = mv^2/2), the concept of "absorbing a force" is not at all clear. You will have to explain what that means.

 Indeed and if you are to switch terms you too should be clear. I have already explained that absorbing force is simply the transference of kinetic energy into the damage of structures. Did you miss that? Or if you like it another way, the resistance a given substance has to a  force, in this case a projectile. The pedantic posturing here seems a bit hollow for anyone who is yet to cite anything concrete in terms of the jet theory

[Andrew Mason]

Indeed and if you are to switch terms you too should be clear. I have already explained that absorbing force is simply the transference of kinetic energy into the damage of structures. Did you miss that? Or if you like it another way, the resistance a given substance has to a  force, in this case a projectile. The pedantic posturing here seems a bit hollow for anyone who is yet to cite anything concrete in terms of the jet theory

So let's talk about transferring kinetic energy then rather than absorbing force.  What is your point?

Bullet Kinetic Energy is transferred to the bullet as heat (deforming the bullet) and to the damage to the head.  Some of that kinetic energy is transferred into pressure energy (pressure x volume = energy) of the head contents just before the skull ruptures.  When the skull ruptures, the brain and blood gain kinetic energy when the pressure is released and a small amount of kinetic energy is given to the recoiling head. 

[Matt Grantham]

 Szamboti's 2012 response pretty much puts and end to Alvarez. Shall we go through the details of all of Alvarez's mistakes in using a melon instead of  human head.

 From Szamboti

By using
the words “if 10% of the incoming kinetic energy were used to propel 10% of the mass of the
melon forward” Dr. Alvarez shows that he simply assumed the values he needed to make the
equation work in the direction he wanted it to go. If he had proof of what he was saying he
would have provided it. Since he did testing, which he says validated his theory, he could
have simply weighed the melon beforehand and the remaining melon after the shooting tests,
to find the actual mass of the jet displaced from the melon. He doesn’t mention anything of
the sort

The shear forces generated by the bullet penetrating through
the much higher shear strength of the President’s skull would have precluded the appearance
of a jet effect induced motion in the assassination. This was actually demonstrated in testing
at the U.S. Army's Edgewood Arsenal. Ten human skulls, filled with the same tissue
replicating material as that used by the Army Wound Ballistics Research program, were shot
with 6.5 millimeter ammunition. All ten skulls went forward, in the direction of the bullet,
with none moving backward towards the shooter.