7forever his head snaped forward first if you look at the video
once again your are foolish:
Here is a broader and longer view of the forward snap and the beginning of the rearward lurch, also provided by Alexandre. He used better images for this work. The sequence starts at 311 and continues through 317. View it repeatedly, and you will see not only JFK's motions, but the lack of corresponding motions by any of the other passengers. This gives the lie to ideas that an deceleration of the car caused any of the motions
—it didn't happen that way.
I also think I see a quick little rearward snap in 314 (sort of a "pop-back") right after the forward snap. If so, it would likely be a visible manifestation of the jet effect. Comments by viewers would be appreciated.
Alexandre has also provided separate small-scale animations for 311
–316, 312
–313, 313
–314, and 314
–315. I encourage anyone who wants to focus on details (where the Devil is in this case) to study these little sequences. To my eye, they show even more strongly the snap in 313, a little pop-back at 314, and the beginning of the big lurch in 315.
311
–316
312
–313
313
–314
314
–315