Energy Energy is the name given to the ability to do work. Work and energy are measured in the same units. People often confuse energy, power, and force. Force is a push or a pull on an object or body. The amount of work is determined by the strength of the force used and the distance through which it moves. Power measures the rate at which work is done.

There are 2 different kinds of energy. Potential energy is often called stored energy. It represents work that has already been done. A rock lying on the top of a cliff has potential energy and so does the cartridge in a loaded rifle. When the rock topples over the cliff or the gun fires, potential energy becomes kinetic energy. Kinetic energy is the energy of movement.

The rock on the edge of the cliff had to be placed in that position and the gun had to be loaded. If you stretch an elastic band between your fingers, it represents potential energy. Let the elastic band snap back into its normal position, and the potential energy is changed to kinetic energy as long as the band keeps moving. The word kinetic comes from a Greek word meaning to move.

A moving train or a high speed electron in a TV tube exhibits kinetic energy. Changes in energy. Energy is constantly changing from the potential to the kinetic state and back again. Every change in the universe represents the change of energy from one form into another. This process is called the transformation of energy.

For example, let us analyze what happens when a boy shoots a stone from a slingshot. When he pulls back the rubber band, the potential energy in the boy is changed to the potential energy in the stretched band. When he releases the band, the potential energy of the band is changed to kinetic energy of the thrown stone. When the stone strikes a target, the kinetic energy becomes heat energy..