Work
Work is done when a force acts on a moving body. Work is done whenever a force moves something.
Everyday examples of work include walking up stairs, lifting heavy objects, pulling a sledge and pushing a shopping trolley.
Calculating work done
Here is the equation that relates to work done, force applied, and distance moved in the direction of the force.
\(\text{Work done} = {\text{Force}}\times{\text{Distance}}\)
\(\text{W} = {\text{F}}\times{\text{d}}\)
where
W is measured in joules, J
F is measured in newtons, N
d is measured in metres, m
In the example above, 10 N is applied to move the box 2 m.
Work done = 10 × 2 = 20 J
The triangle above will help you to rearrange the equation.
Work done has the same units as energy - joules. This is because energy is the ability to do work. You must have energy to do work. You do not have to do work if you have energy though - potential energy does not do work. Specifically, in the example above, a person could not push the box (and so do work) without energy. Work done is equal to energy transferred, ie work = energy transferred.
An object can possess energy as a result of its:
- position (potential energy)
- motion (kinetic energy)
- deformation (elastic energy)