Falling rocks from a mountain top possess potential energy when they are at rest on the mountain top and kinetic energy as they fall.

Here's the breakdown:

* Potential Energy: This is stored energy due to an object's position or state. The rocks on the mountaintop have potential energy because of their height above the ground. The higher the rock, the more potential energy it has.

* Kinetic Energy: This is the energy of motion. As the rocks start to fall, they gain speed and therefore kinetic energy. The faster they fall, the more kinetic energy they have.

As the rocks fall, their potential energy is converted into kinetic energy. This is a classic example of the conservation of energy, where energy is transformed from one form to another, but never lost.