**Work** is done when a force acts over a distance. Its units are given in Newton-metres, or Joules (J). If force is variable and given as a function (with x being the position), and *b* - *a* is the interval over which the force acts, **work** is given by

or more generally (as a vector line integral)

If the force is constant and always parallel to the displacement vector, this simplifies to

- or

## Formulae for work[]

- , where
*U*is potential energy - where
*P*is power - where
*τ*is torque and*θ*is the angle across which torque is applied - (if
*τ*is constant) - for a spring obeying Hooke's law
- where
*P*is pressure and*a*and*b*are initial and final volumes