Energy Transfer & Work (WJEC GCSE Science (Double Award)): Revision Note
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 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
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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.
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 Tips and Tricks
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
Use the formula triangle to help rearrange the equation. Cover up the quantity you need.
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