Re: Velocity of a falling bullet

On Wed, 03 Dec 2003 14:23:09 GMT, "Doug Kanter"
<[EMAIL PROTECTED]> wrote:

>"Don A. Gilmore" <[EMAIL PROTECTED]> wrote in message
>news:[EMAIL PROTECTED]
>
>>
>> Terminal velocity can only apply in a resisting medium.  A bullet
>travelling
>> upward in a vacuum will indeed come to a stop, but all of the energy will
>be
>> returned to it in its fall...every bit of it.  It will reach the ground at
>> exactly its muzzle velocity.  Perhaps your high school physics didn't
>cover
>> this.
>>
>> Don
>>
>>
>
>But muzzle velocity is assisted by the explosion of the gunpowder. How
>likely is it that on the way back down, other factors will influence the
>slug to have the same speed at which it left the gun?

---
In a vacuum the only force which needs to be considered is gravity.

Think about it like this:

Since gravity is always there, regardless of what caused the projectile
to accelerate to its muzzle velocity, once that accelerating source goes
away gravity takes over and starts decelerating the projectile.  In a
vacuum the shape or volume of the projectile will be unimportant, so the
only force acting on it will be gravity.  If the gun was pointed
"straight up" when the projectile was fired, then its path will lie on a
straight line going through the center of the earth.  When the
projectile eventually comes to a stop it will retrace its path back
toward the center of the earth and, because it experiences the same
force accelerating it that it did when it was being decelerated it will
be moving at precisely the same velocity when it goes the same distance
down that it went up.  Matter of fact, when it travels down as far as it
did when it started going up at the bottom of the gun barrel it will be
going faster than it was when it left the muzzle of the gun.
      
-- 
John Fields