Problem 29                      Due on 4/19/00

	In this problem we integrate a
second order differential equation as
a system of first order equations.

	Consider the motion of a cannon ball
which is fired straight up into the air.
The initial velocity is given by Uo, the
mass is M, and the radius is R.  We want
to calculate how high the cannon ball gets,
and how long it takes before it hits the
ground again (e.g., how long do we have to
get out of the way).  The motion of the ball
is governed by Newton's equations of motion,
and in addition to the force of gravity we
also have an air drag.  This drag is given by:

F = - sign(U)*0.5*pi*R^2*U^2*dens_air

If the mass M is 3000g, the initial velocity
Uo is 2e4 cm/s, the density of air is 0.001 g/cm^3,
and the radius is 10cm, calculate the maximum
height and the time for the ball to hit the
ground again.