CL wrote:
> Simon wrote:
> 
>> The muzzle velocity isn't important, just the velocity of the bullet 
>> on it's way back down. 
> 
> 
> If I remember Mr. Science, correctly, the time / speed / distance thingy 
> plots out as a bell curve where the apex is zero speed, zero 
> acceleration.  If you draw a line parallel to the base through both legs 
> of the curve, the speed is the same and the acceleration is exactly the 
> opposite -- e.g. traveling at the same speed, but it is decelerating at 
> the same rate on the way up that it is accelerating on the way down.

This is true except for the effect of air resistance.  Air resistance is 
a force that always acts opposite to the direction of motion.  And it 
depends on speed.  Common models for air resistance assume that it is 
proportional to velocity.  Thus, the air resistance force acting on a 
body increases as it accelerates in free fall.  At a certain point, the 
two balance, and acceleration ceases.  This point is known as "terminal 
velocity".

Compare these two differential equations, where y is the vertical height 
of the object, and t is time, m is the object's mass, and g is 
acceleration due to gravity, and k is an air resistance coefficient 
which depends in a very complicated way on the shape of the object among 
other things.

y''(t) = -g/m

y''(t) = -g/m - k*y'(t)

The solution to the first is the parabola you describe; the solution to 
the second is more complicated, but is not a parabola.

> Then again, I have two liberal arts degrees and a non-science advanced 
> degree, too ... no one needs to go "engineer" or "physicist" on us ...

OK, if you say so.

-- 
Curt Fischer