# physics

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

• physics -

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.

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