GCSE Combined Science revision · Physics: forces, waves and magnetism

Work done

The idea

When a force causes an object to move through a distance, work is done on the object and energy is transferred: W = Fs, where s is the distance moved along the line of action of the force. One joule of work is done when a force of one newton causes a displacement of one metre (1 J = 1 N m). Work done against friction causes a rise in temperature.

Find the force and the distance in its direction.
Use W = Fs.
Give the answer in joules.

Watch out If the object does not move, no work is done, even if a force is applied.

See it worked

Worked example

A person pushes a trolley with a force of 40 N for 15 m. Calculate the work done.

W = Fs = 40 × 15.
= 600 J.

Answer 600 J

Your turn

Question 1Calculator allowed2 marks

A crane lifts a 5000 N load through 12 m. How much work does it do, in joules?

Question 2Calculator allowed2 marks

800 J of work is done pushing a box 20 m. What force was used, in newtons?

Question 3Calculator allowed1 mark

What happens to a bike's brakes when work is done against friction?

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