Factors Affecting Braking Distance
Build confidence in Factors Affecting Braking Distance for GCSE Physics with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Braking distance increases with speed and with poor road or vehicle conditions, and large braking forces can cause skidding.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
Braking distance is affected by the condition of the road, the condition of the vehicle, and the size of the braking force applied.
Wet or icy roads reduce the friction between the tyres and the road surface, so the braking force is smaller and the braking distance is longer. Worn tyres and worn brakes have the same effect.
When a force is applied to the brakes, work done by friction between the brakes and the wheels reduces the kinetic energy of the vehicle, and the temperature of the brakes increases. Large decelerations require large braking forces, which may cause the brakes to overheat or the driver to lose control of the vehicle.
Revision notes
Factors affecting braking distance
Road conditions: wet or icy roads reduce friction between tyres and road, lengthening the braking distance.
Vehicle condition: worn tyres or worn brakes reduce the braking force available. A greater braking force gives a shorter braking distance.
The energy transfer
When the brakes are applied, work is done by friction between the brakes and the wheels.
This reduces the kinetic energy of the vehicle and increases the temperature of the brakes. All the kinetic energy must be transferred before the vehicle stops.
Dangers of large decelerations
Stopping in a short distance requires a large deceleration and therefore a large braking force.
Large braking forces may cause the brakes to overheat, or the driver to lose control of the vehicle if the wheels lock and skid.
Key points
- Wet or icy roads lengthen braking distance.
- Worn tyres and brakes lengthen braking distance.
- A greater braking force shortens braking distance.
- Work done by friction reduces kinetic energy.
- The temperature of the brakes increases.
- Large braking forces risk overheating and skidding.
Worked examples
Example 1
Explain why braking distance is longer on an icy road. [2 marks]
Model answer
Ice reduces the friction between the tyres and the road surface (1 mark), so a smaller braking force can be applied and the vehicle takes a greater distance to stop (1 mark).
Example 2
Describe the energy transfer that occurs when a car brakes. [3 marks]
Model answer
Work is done by the friction between the brakes and the wheels (1 mark). This reduces the kinetic energy store of the car (1 mark) and increases the thermal energy store of the brakes, so their temperature rises (1 mark).
Example 3
Explain two dangers associated with large decelerations. [2 marks]
Model answer
The brakes may overheat because a large amount of energy is transferred to them very quickly (1 mark). The driver may also lose control of the vehicle if the wheels lock and it skids (1 mark).
Common mistakes
Saying ice increases friction.
Ice reduces friction, which is why braking distance increases.
Confusing braking and thinking distance factors.
Road and vehicle condition affect braking; tiredness and alcohol affect thinking.
Not naming the energy stores.
Say kinetic energy store and thermal energy store explicitly.
Giving only one danger of large decelerations.
Overheating brakes and loss of control are both examinable.
Exam tips
- Separate the factors affecting thinking and braking distance.
- Name both energy stores in the transfer.
- Give both dangers of large decelerations.
- Link reduced friction to a smaller braking force.
Key terms
- Braking distance
- The distance travelled while the brakes slow the vehicle.
- Friction
- The force between tyres and road, and between brakes and wheels.
- Deceleration
- Negative acceleration when slowing down.
- Kinetic energy store
- The energy store reduced by braking.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.