Work, Energy and Power — Definition

Definition

Work is energy transferred by a force acting through a displacement. For a constant force on a particle, its value is the force magnitude multiplied by displacement and by the cosine of the angle between them.

Energy describes the capacity of a system to produce changes and includes kinetic, potential and internal forms. Power is the rate of energy transfer or work, rather than a separate store of energy. Work and energy use joules; power uses watts.

A useful analysis identifies the force, the displacement, the system boundary and the time interval before applying a formula or comparing machines.