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Now that we are finally trying to deal with the type of physics intendedcut
by the original post, I can tell you the results of some experiments my
friends and I did when I was in grad school. We were not working with
the bullet fired in the air problem; rather, we were working with the
penny dropped off the Empire State Building problem. It is still
commonly stated that if a penny were dropped from the Empire State
Building and it were to land on a person's head, it would kill the
person. Sometimes the myth even states the penny will penetrate clear
through the person.
The bullet and penny problem are essentially the same... What is the
likely terminal velocity of a falling penny (or bullet).
One source of this penny claim is when someone with a little physics
knowledge calculates the velocity at which a penny will land if it has
acceleration g all the way from release to landing. Of course this is
not true because of air friction. Some who try to include air friction
assume the penny falls edgewise because that presents the least air
friction and they assume the penny will assume that orientation as it
falls.
We were never able to get a penny to fall edgewise. It very quicklycut
tumbles, and it tumbles rapidly. It's terminal velocity is very slow,
about 15 mph, roughly 20 ft/s, roughly 6 m/s. I can ride my bike that
fast. At that time a penny was copper. Today with copper-coated zinc
pennies I presume the terminal velocity is lower yet. Anyway, a penny
dropped from a high place is not going to kill someone.