Factors affecting braking distance 1 — AQA GCSE Physics
Test yourself on Factors affecting braking distance 1 with AQA GCSE practice questions.
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Factors affecting braking distance 1 explained
The braking distance depends on the friction force available at the tyres and at the brakes.
Read the full explanation
On a wet or icy road, a film of water or ice between tyre and surface lowers the friction, so the maximum braking force is smaller. Worn tyres with shallow tread cannot clear water, and worn brake pads or discs grip the wheel less firmly. In each case the same kinetic energy, ½ m v², has to be removed by a smaller force. Since work done = braking force × braking distance, a smaller force means the distance must be larger. Greater mass works the same way, because more kinetic energy has to be removed in the first place. Worn pads also overheat and fade sooner, so the braking force can fall further part way through a long stop.
Your focus
- Explain why a wet road increases the braking distance, starting from the friction at the tyres.
- Link a reduced braking force to a longer braking distance using work done = force × distance.
- Give one road condition and one vehicle condition that lengthen the braking distance, and say why each does.
Factors affecting braking distance 1 exam tips
Marking Points
- one mark for naming wet or icy road conditions as an adverse condition
- one mark for naming worn brakes or worn tyres as poor vehicle condition
- one mark for stating that the friction force between the tyres and the road is reduced
- one mark for linking the smaller braking force to the longer distance needed to remove the kinetic energy
Examiner Tips
- 💡Build the chain: condition, then friction, then braking force, then distance.
- 💡Use the words 'friction between the tyres and the road' rather than just 'grip'.
- 💡If the question offers marks for an explanation, bring in work done = force × distance.
Common Mistakes
- answering 'bad weather' alone, which the mark scheme ignores
- saying ice makes the car heavier or the brakes colder
- explaining a braking factor through the driver's thinking distance
- claiming the brakes stop working altogether on an icy road