Energy
Energy, capacity of matter to perform work as the result of its motion or its position in relation to forces acting on it. Energy associated with motion is known as kinetic energy , and energy related to position is called potential energy . Thus, a swinging pendulum has maximum potential energy at the terminal points; at all intermediate positions it has both kinetic and potential energy in varying proportions. Energy exists in various forms, including mechanical (see Mechanics ), thermal (see Thermodynamics ), chemical (see Chemical Reaction ), electrical (see Electricity ), radiant (see Radiation ), and atomic (see Nuclear Energy ). All forms of energy are interconvertible by appropriate processes. In the process of transformation either kinetic or potential energy may be lost or gained, but the sum total of the two remains always the same. A weight suspended from a cord has potential energy due to its position, inasmuch as it can perform work in the process of falling. An electric...