35. Scenario 4Śrear hit provides only snap
Frontal scenario 4 is the long shot of the group. It is a modified James Files scenario where a first bullet, from the rear, creates only the snap and a second bullet, from the front, creates everything else. The difference from the Files scenario is that the frontal hit is here forced to create a forward-moving cloud and large fragments, because that is what happened.
The calculations and their problems
This scenario can be calculated with a modified scenario SL6L similar to that used in the last section, only with the function of the two bullets reversed. The first bullet (from the rear) was taken to be a Mannlicher-Carcano, with mbullet = 161 gr and vbullet = 1800 ft s-1. The second bullet (from the front) was taken to be a Remington .221 for the XP-100 Fireball, with mbullet2 = 50 gr, vbullet2 = 2650 ft s-1, and vbulletafter2 = -200 ft s-1.The other settings now become mhead = 6 lb, Θv = 12░, Θh = 9░, Θv2 = 9░, Θh2 = 118░, mcloud = 0.3 lb, dsnap = 2.4 in, and PE = 300 ft-lb.
The procedure is hard to implement, though, because the second bullet has to create its own snap as it moves through the head. This adds a fifth time interval to the sequence that must fit within a single Zapruder frame, and for all intents and purposes extends the total time to the point that there is no ore room for a lurch. The time extension is made worse by the fact that the second lurch is much slower than the first (other factors being equal) because the second shot has a smaller X-component of its velocity. For example, a test calculation gave 61 ms for the second snap, vs. 34 ms for the first. Obviously, things didn't happen this way, because there was time for a lurch. The total of the times can be reduced by allowing the first snap and the second to overlap. But this makes no sense physically, for the head clearly snapped forward by >2.2 in.
Another problem, likely insurmountable, is the distance of the snaps. With two snaps and the first part of the lurch now summing to the 2.2 in seen in the film, it is impossible to determine, even to estimate, each one separately. There are too many variables here. This complex, underdetermined scenario 4 collapses under its own weight, and will not be considered further here.
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