You are trying to find out how high you have
to pitch a water balloon in order for it to burst
when it hits the ground. You discover that
the balloon bursts when you have pitched it
to a height of 18 m.
With what velocity did the balloon hit
the ground? The acceleration of gravity is
9.8 m/s^2. The positive direction is up, so the
velocity when it hits is negative.
Answer in units of m/s.
set PE at h=18 to KE at h=0
mgh = 1/2 mv^2
18*9.8 = 1/2 v^2
v = 18.78 m/s