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Q:
Getting Back to Bullets! If a bullet is shot into the air... and falls back down slower, could it still injur someone if it hits them falling back down?
- Roni
A:
Yes, a bullet shot up into the air will encounter air resistance on the
way up, which resists its upward motion. It also encounters resistance
on the way down, resisting its downward motion. Both of these effects
result in a slower bullet speed when it returns. Nonetheless, many of
these bullets are still traveling fast enough to kill. Each year,
people die on New Year's Eve because stray bullets from celebrants'
gunfire strike them.
The actual speed of the returning bullet depends on a lot of
things. In the absence of air resistance, the speed of the bullet out
of the gun will be the same as it is coming back down, and so the
muzzle velocity of the bullet affects its return speed. Also, the shape
of the bullet affects the air resistance. Winds may blow the bullet off
course but probably not change the speed noticeably. If the bullet is
very dense (and many are made of lead), the air resistance will change
its speed less than if it were less dense (as in a rubber bullet).
Tom
(published on 10/22/2007)
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