AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
The stopping distance of a vehicle is the sum of the distance the vehicle…
Full specification wording
Stopping distance: The stopping distance of a vehicle is the sum of the distance the vehicle travels during the driver’s reaction time (thinking distance) and the distance it travels under the braking force (braking distance). For a given braking force the greater the speed of the vehicle, the greater the stopping distance.
Stopping distance is the total distance a vehicle travels from the moment a driver sees a hazard until the vehicle comes to rest.
Checked against the AQA 8464 specification (opens in a new tab) on .
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Stopping distance is the total distance a vehicle travels from the moment a driver sees a hazard until the vehicle comes to rest. 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.
What earns the marks
- 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.
Common mistakes and how to put them right
Confusing thinking distance with braking distance.
Put it right 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.
Put it right by adding thinking distance to braking distance.
Thinking that a greater speed only increases braking distance.
Put it right by noting that thinking distance also increases because the vehicle travels faster during the same reaction time.
Exam 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.
Try the lesson
The start of the Stopping distance: The stopping distance of a vehicle is the sum of the distance the vehicle travels during the driver’s reaction time (thinking distance) and the distance it travels under the braking force (braking distance). For a given braking force the greater the speed of the vehicle, the greater the stopping distance. lesson, made from checked teaching notes for this specification point.
Have a go first
A car has a thinking distance of 9 m and a braking distance of 21 m. What is the stopping distance of the car?
Listen
Stopping distance is the total distance a vehicle travels from the moment a driver sees a hazard until the vehicle comes to rest. 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. A strong answer earns marks for these 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. A common slip: Confusing thinking distance with braking distance. Instead, linking thinking distance to reaction time before braking and braking distance to the distance covered while the brakes act. Exam tip: Write the equation stopping distance = thinking distance + braking distance before substituting values.
See it
Key words
Say what each word means before you turn the card.
Stopping distance
Try answering aloud or in your head before turning the card.
Thinking distance
Try answering aloud or in your head before turning the card.
Braking distance
Try answering aloud or in your head before turning the card.
See every definition
- Stopping distance
- The sum of the distance the vehicle travels during the driver's reaction time and the distance it travels under the braking force.
- Thinking distance
- The distance the vehicle travels during the driver's reaction time, before the brakes are applied.
- Braking distance
- The distance the vehicle travels while the braking force acts on it.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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Test your understanding of Stopping distance: The stopping distance of a vehicle is the sum of the distance the vehicle travels during the driver’s reaction time (thinking distance) and the distance it travels under the braking force (braking distance). For a given braking force the greater the speed of the vehicle, the greater the stopping distance.
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