Superfreaks/ACRA: Superfreaks Season 3 #1

Martin phippsmartin at
Sat Oct 6 03:53:35 PDT 2007

On Oct 6, 6:54 am, Eagle <ea... at> wrote:
> Tom Russell <milos_par... at> writes:
> > 1. The bullet only weighed a few ounces and the head nearly fourteen
> > pounds.  REGARDLESS of speed, bullets DO NOT cause heads and bodies to
> > throw themselves backwards as we often see in movies.  The head would
> > offer too much resistance.  It's simple physics.
> Yup.  Just as an exercise, here's how I'd work through the problem.
> I don't feel like searching to see what type of rifle Oswald used, so
> let's assume the heaviest likely case, a .45 or .50 caliber rifle with an
> elephant cartridge.  That bullet would probably weigh around 500 grains,
> or 32 grams.
> Let's assume that your estimate of 14 pounds for the head is correct.
> That's 6350 grams, or 6.4 kg.
> The momentum of the bullet is given by mass times velocity.  Again, I
> don't feel like doing a lot of research, so let's assume that the muzzle
> velocity of the rifle is somewhere vaguely in the range of what you'd get
> from a Barrett M95, since that's what turned up in a Google search.  It
> has a muzzle velocity of 2800 feet per second, or 850 m/s.
> That gives a bullet momentum of about 27 kg * m/s.
> Assuming the bullet does not add appreciably to the mass of the head, the
> worst-case for head movement would be a complete momentum transfer (no
> exit wound), which would result in a head speed immediately after
> inelastic collision of 4.2 m/s, or 9 mph.  That means that in this worst
> case (which isn't correct, since we know there was an exit wound and
> therefore the bullet didn't transfer all of its momentum to the head), you
> would expect as much head movement as you'd get from a sudden decrease in
> the speed of the car of about 10 mph.  That's some, but not much, and the
> neck is likely to absorb a lot of that momentum.

Actually, no.  When a car decreases suddenly by about 10 mph, the
entire body moves forward a bit so you wouldn't notice any movement of
the head compared to the rest of the body.  Plus, even if the car
stops suddenly, your seatbelt would slowly absorb the shock.  In
practice, cars do not slow down quite so suddenly and your body has
time to absorb the shock.


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