Energy Transfer & Work

When a force acts on an object causing it to move then energy is transferred
This energy transfer is known as the work done
- If a force is applied to an object but doesn’t result in any movement, no work is done
- Work done is measured in joules (J) or newton-metres
The total amount of energy remains constant, in the absence of thermal energy transfer
Energy cannot be created or destroyed
- This is known as the conservation of energy

Work Done to Move a Box

work-force-object, IGCSE & GCSE Physics revision notes

Work is done when a force is used to move an object in the same direction it is acting

The formula for work done is:

Work = force × distance moved in the direction of the force

$W = F d$

Where:
- W = work done in joules (J) or newton-metres (N m)
- F = force in newtons (N)
- d = distance in metres (m)

Worked example

A car moving at speed begins to apply the brakes. The brakes of the car apply a force of 500 N which brings it to a stop after 23 m.

braking-work, IGCSE & GCSE Physics revision notes

Calculate the work done by the brakes in stopping the car.

Answer:

Step 1: List the known quantities

Distance, d = 23 m
Force, F = 500 N

Step 2: Write out the equation relating work, force and distance

W = F × d

Step 3: Calculate the work done on the car by the brakes

W = 500 × 23

W = 11 500 J

Examiner Tip

Remember to always convert distance into metres and force into newtons so that the work done is calculated in the correct units (joules or newton metres)

Higher tier students can use this formula triangle to rearrange the work equation.

Work Formula Triangle

Work triangle (3), IGCSE & GCSE Physics revision notes

Use the formula triangle to help rearrange the equation. Cover up the quantity you need.

Energy Transfer & Work (WJEC GCSE Physics: Combined Science)

Revision Note