Work is the overcoming of a resisting force over a distance. The work performed when a force F overcomes an equal resisting force along a distance s in the same direction equals Fs, i.e., F times s.


If the force is not in the direction of the motion, only the vector component of F in that direction enters the calculation. Thus, If a force F acts on a body and the body moves a distance s at an angle θ to the line of action of the force then the work done W is defined as being the product of the force, distance, and the cosine of the angle, i.e.,

    W = Fs cosθ


The unit of work, or energy transfer, is the joule (J). One joule is the energy transferred when a force of 1 newton is applied over a distance of 1 meter in the direction of the force. This makes the joule the equivalent of kg m2 s-2 with dimensions of [M]1 [L]2 [T]-2.


Energy can be defined as the ability to perform work.