[ALASKA]

You should have quit before you started. As I said, JFK's head (body) was ALREADY moving toward the front and downward at the time of impact. This was his reaction to the shot that transited his neck. The impact of the bullet to the head instantly and VIOLENTLY drives his head toward the left rear of the limo. The clip you posted is out of context; watch the entire Zapruder film.

[Shooter 2.5]

Bullsh!t with a capital B. YOU post the previous frames. Kennedy’s head moved 2.3 inches from one frame to the next. That’s moving 2.3 inches to the front in one eighth of a second.

Do your math.