work

In physics, a transfer of energy from one system to another, caused when the point of application of a force moves in the direction of the force. Work is done when, for example, a wire is stretched, or a gas is compressed, or a ball is thrown. No work is done when the point of application moves at right angles to the force; for example, when an object is whirled in a circle on the end of a piece of string (a centripetal force, or centre-seeking force, acts on the object, while its motion is always at right angles to the line connecting it to the centre of the circle). Although work is measured in joules, it should not be confused with energy (the capacity to do work, which is also measured in joules) or with power (the rate of doing work, measured in joules per second).

Work is equal to the product of the force used and the distance moved by the object in the direction of that force. If the force is F newtons and the distance moved is d metres, then the work W joules is given by: W = Fd. For example, the work done when a force of 10 newtons moves an object 5 m against resistance is 50 joules.