Falling rocks from the top of a mountain possess gravitational potential energy when they are at rest at the top, and this energy transforms into kinetic energy as they fall.

Here's a breakdown:

* Gravitational Potential Energy: This energy is stored due to the rock's position in a gravitational field. The higher the rock is, the more potential energy it has.

* Kinetic Energy: This energy is the energy of motion. As the rock falls, its speed increases, and therefore, its kinetic energy increases.

The total energy of the rock (potential + kinetic) remains constant throughout the fall, assuming no air resistance. This is a classic example of the conservation of energy.