Physics  Free Fall
posted by Brianna on .
A stone was thrown into the air and returned after 4.2 seconds.
a) At what speed was the stone thrown? (20.6) < i got that right.
b) How high did the stone go? (21.6 m)
i don't know how to get b. what steps do i do?

The stone with an initial velocity, v, has a kinetic energy of (1/2)mv².
When at the top, velocity = 0, but the potential energy is mgh.
So equate energies to get
mgh = (1/2)mv²
Solve for h.