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Work definition

Work $$(W)$$ is done by a force when a force moves an object.

More precisely, for work to be done, a force must be applied to an object and the object must move in the direction of the force.

$$$\begin{align*}\Tblue{\text{work done}} =& \Tred{\text{force}} \times \Tgreen{\text{distance moved in direction of force}} \\ \Tblue{W}=&\Tred{F}\times\Tgreen{d}\end{align*}$$$

  • If you lift a book from a table you apply a force on the book and it moves in the direction of the force. Work is done.
  • If you push against a wall, you exert a force on the wall but no movement occurs. There is no work done.
  • A ball continues to move after it has been kicked. It is still moving but there is no longer any force acting on it. No work is being done.

Work is a scalar quantity (it has no direction).

The definition in physics contrasts with the use in everyday English. Any sort of task undertaken for a salary is considered to be work.

A crane does work by lifting objects like this container.
A crane does work by lifting objects like this container.