Energy is one of the central themes in science. There are many forms of energy, each with its own specific definition. Any form of energy can be converted into one of the other forms. This is the law of conservation of energy, which states that energy is conserved in any system. A general definition for energy is the ability to do work. This definition is oversimplified, for not all forms of energy can actually do work. It does, however, demonstrate the important relationship between energy and work.

Work is performed whenever a force moves an object. The amount of work done can be calculated by multiplying the magnitude of the force acting on an object by the distance the object moves. Using the English system of measurement, the force is measured in pounds (lb) and the distance is measured in feet (ft). The product of the...