Find the gravitational potential energy of the stone. A stone weighing 1.5 kilograms is resting on a rock at a height of 20 meters above the ground. The stone rolls down 10 meters and comes to rest on a patch of moss. The gravitational potential energy of the stone on the moss is joules. (Use PE = m * g * h, where g = 9.8 N/kg.)

We can ignore all that business about resting on the rock and

rolling down part of the way and then resting on the moss.

Its potential energy right now doesn't depend on what happened

to it yesterday. We don't care.

All we care about is that we're walking along in the park and we

notice a 1.5kg rock lying in moss 10 meters above the ground.

Gravitational potential energy

= (mass) · (gravity) · (height)

= (1.5 kg) · (9.8 N/kg) · (10 m)

= 147 (kg · N · m / kg)

= 147 joules