physics
posted by dave .
An object is dropped from a height of 12m.At what height is the rock kinetic energy and its potential energy be equal?

assume potential energy = 0 when h = 0
U = m g h
U top = total energy = m (9.8 * 12)
=
U + Ke = U top
so
if U = Ke then
U = U top /2 = m (9.8 * 6)
so
at h = 6 meters
In other words, when it loses half its original potential energy, the Ke = U and that is halfway down.