Stopping distance — AQA GCSE Combined Science
Test yourself on Stopping distance with AQA GCSE practice questions.
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Stopping distance explained
Stopping distance is the total distance a vehicle travels from the moment a driver sees a hazard until the vehicle comes to rest.
Read the full explanation
It has two parts. Thinking distance is the distance travelled during the driver’s reaction time, before the brakes are applied. Braking distance is the distance travelled while the braking force acts. So stopping distance = thinking distance + braking distance. For a given braking force, a higher speed increases both parts: the vehicle travels further during the same reaction time, and it takes more distance to stop once braking begins. For example, at 30 mph a typical stopping distance is about 23 m, while at 60 mph it is much greater.
Your focus
- State the two components of stopping distance and how they combine.
- Explain how increasing speed affects thinking distance and braking distance for a given braking force.
- Apply the stopping distance relationship to compare or calculate distances in a road-safety context.
Stopping distance exam tips
Marking Points
- Define stopping distance as thinking distance plus braking distance.
- Describe thinking distance as the distance travelled during the driver’s reaction time before the brakes are applied.
- Describe braking distance as the distance travelled while the braking force acts on the vehicle.
- Explain that for a given braking force, increasing speed increases stopping distance.
- Use the relationship stopping distance = thinking distance + braking distance in a calculation or comparison.
- Recognise that reaction time and braking force are separate factors that affect the two parts of stopping distance.
Examiner Tips
- 💡Write the equation stopping distance = thinking distance + braking distance before substituting values.
- 💡When comparing speeds, state that both thinking distance and braking distance increase as speed increases for a given braking force.
- 💡Use the correct units, such as metres (m) for distance and seconds (s) for time, and keep them consistent throughout a calculation.
Common Mistakes
- Confusing thinking distance with braking distance; correct this by linking thinking distance to reaction time before braking and braking distance to the distance covered while the brakes act.
- Assuming stopping distance is only braking distance; correct this by adding thinking distance to braking distance.
- Thinking that a greater speed only increases braking distance; correct this by noting that thinking distance also increases because the vehicle travels faster during the same reaction time.