Work is done when energy is transferred from one store to another. Work is also done when a force causes an object to move. When work is done against frictional forces acting on an object, the object's temperature increases. For example, a person's hands warm up when they are rubbed together repeatedly.
To calculate the work done on an object when a force moves it, use the equation:
work done = force × distance
This is when:
Note that one joule of work is done when a force of 1 N causes a movement of 1 m. This means that work done can also be measured in newton-metres (Nm):
Take care not to confuse newton-metres (a unit of work done) with newton meters (calibrated spring balances used to measure weights).
A doctor weighs 600 N. A lift moves her 40 m to the top floor of a hospital. Calculate the work done on the doctor by the lift.
In a scrum, a rugby team pushes the other team backwards 5 m using a force of 1000 N. Calculate the work done moving the other team.