The physics of "back and to the left"

[Gerry Down]

Here's a nice little demonstration of why a bullet from the grassy knoll could not have flung JFK back into his seat. A bullet has just way too little mass to move an adults head so violently back and to the left. A bullet only has enough mass to move an adult head a little bit - which is why Oswalds bullet to JFKs head was only able to move JFKs head forward about 2 inches as seen in the Zapruder film when it is slowed down.

https://www.youtube.com/shorts/WvqTnqR2kn0

[Joe Elliott]

Here's a nice little demonstration of why a bullet from the grassy knoll could not have flung JFK back into his seat. A bullet has just way too little mass to move an adults head so violently back and to the left. A bullet only has enough mass to move an adult head a little bit - which is why Oswalds bullet to JFKs head was only able to move JFKs head forward about 2 inches as seen in the Zapruder film when it is slowed down.

https://www.youtube.com/shorts/WvqTnqR2kn0

And what is the maximum speed a Carcano bullet should push JFK’s head forward? Here are my calculations. Note, I don’t use the more scientific metric units but the physics still work using ‘pounds’ and ‘mph’ (miles per hour).

Mass of the bullet: About 10 grams, or about one third of an ounce, or about one fiftieth (1/50) of a pound.
Speed of the bullet: 1400 mph
Mass of JFK’s head, about 8 pounds.

Speed that the bullet could push JFK’s head:

N (momentum) = M (mass) * V (velocity)
V = N / M

Momentum of bullet = 1/50 * 1400 mph = 28 pounds * mph
Mass of JFK’s head = 7 pounds
Speed of JFK’s head if all the momentum of the bullet is received by the head = 28 pounds * mph / 7 pounds = 4 mph

The actual speed of JFK’s head moving forward between frames 312 and 313? 2 mph

Note, during z312 – z313, only JFK’s head moves forward. The torso does not. This was determined by Physics graduate student William Hoffman working with Josiah Thompson on the book ‘Six Seconds in Dallas’.

This accords well with Larry Sturdivan’s estimate who, based on his work with ballistics, judged that only half the momentum of the bullet would be absorbed by JFK’s head. The bullet fragments that exited from the head would have half the speed of the bullet at the initial strike, about 700 mph and these fragments would dent the windshield frame, crack the windshield and a third fragment slightly wounded James Tague.

A bullet from the front doesn’t work because:

•   Unlike the initial forward movement, both the head and the torso moved backwards during z313 – z318. This would require too much momentum from a single bullet, unless a highly implausible anti-tank weapon was used.
•   The speed of JFK’s head backwards is not constant but starts slowly, around 0.5 mph and over the next quarter of a second gradually builds up to 1.8 mph. This would be consistent not with one bullet, but a series of bullets, each striking the head, once every 1/18 th of second or once every Zapruder frame, adding more and more momentum with each frame. A single shot from a rifle can be fired accurately, but not a stream of bullets from a machine gun.
•   Also, one would expect the head to move backwards with a higher speed at first (with the bullet ‘pushing’ only the head), then at a lower speed (with the bullet ‘pushing’ both the head and the torso). This is the opposite of what is seen in the Zapruder film.

[Gerry Down]

These calculations are very useful. Are you getting them from any particular book or source?

[Robert Reeves]

So what are the physics of JFK's 'random' head snap from right to left shortly after appearing from behind the sign. Approx Z-228 onwards



The random head snap coincides with a white object/projectile appearing to strike his jaw-line.

JFK's left index finger pointing to the shooter. Clue

[Gerry Down]

So what are the physics of JFK's 'random' head snap from right to left shortly after appearing from behind the sign. Approx Z-228 onwards

A gulp of blood going down JFK's windpipe and him suddenly realizing he can't breath.

[Matt Grantham]

 I am thinking any photographic evidence that might exist is preferable My recollection is that bullets tend to move heads

[Steve Barber]

So what are the physics of JFK's 'random' head snap from right to left shortly after appearing from behind the sign. Approx Z-228 onwards



The random head snap coincides with a white object/projectile appearing to strike his jaw-line.

 It's not a "head snap". His entire torso moves from the waist up.  Why do you people continually call it a "head snap" when it isn't?

JFK's left index finger pointing to the shooter. Clue

    That's absurd! He didn't hear the shot that hit him, all he felt was the pain of something happening to him.  Furthermore, A reporter at the shooting of George Wallace was shot through the neck, and his hands are basically in the same position as JFK's, in front of--not "clutching"--his throat.  His left or right index finger extended. Assassin Bremer was in front of Wallace when he shot him, and so was the reporter, and he wasn't pointing at Bremer.

[Steve Barber]

I am thinking any photographic evidence that might exist is preferable My recollection is that bullets tend to move heads

 They can indeed move heads.  The bullet that struck JFK in the head moved his head noticeably forward--it's not an "Optical illusion" as Tink Thompson now says, and all one has to do to see the proof of this is look at a very clear copy of the Orville Nix film, which clearly shows the head moving forward.