The principle of conservation of energy states that energy is neither created nor destroyed, it is just transformed from some types of energy into others. The following visual will help you to understand what is meant by the principle of conservation of energy when a body falls.

The theorem of conservation of mechanical energy states that the work carried out on a body is invested exactly in increasing some type of energy. The visual simulates a moving train.

The educational resource shows a visual about the conservation of energy: the sum of the kinetic energy and the potential energy of a body (mechanical energy) remains constant, provided there are no forces of friction.