What happen to energy after it is used?
No matter how many times energy is changed, it can never be destroyed. But whenever it changes, some of it always escapes. For example, a car engine turns much of the potential energy in petrol into movement. But it also turns some of it into noise and heat, and this escapes as the car moves along. No matter how well machines are designed, they always waste some of the energy that they release.

A waste of energy
As a workman digs a hole with a pneumatic drill, energy escapes in the form of noise and heat, this energy cannot be used.

Energy in a raindrop
The amount of energy in a falling raindrop is about 175 thousand billion times less than the amount of energy of a cruising jumbo jet. But added together at any one time, the energy in all the raindrops falling on Earth is much greater than the energy of all the planes in the air.