Pearson Edexcel · GCSE · Physics
Course version: 1PH0 · Version from Sept 2016
2.32P Estimate how the distance required for a road vehicle to stop in an…
Full specification wording
Topic 2 – Motion and forces: 2.32P Estimate how the distance required for a road vehicle to stop in an emergency varies over a range of typical speeds
Stopping distance is the thinking distance plus the braking distance.
Checked against the Pearson Edexcel 1PH0 specification (opens in a new tab) on .
- Point 31 of 32
Study notes
From the checked teaching notes for this specification point.
The idea
Stopping distance is the thinking distance plus the braking distance. Thinking distance equals speed multiplied by reaction time, so it grows in proportion to speed. Braking distance grows with the square of speed because the kinetic energy to remove, ½mv², rises with v². At 10 m/s a vehicle with a 0.7 s reaction time travels 7 m before braking; doubling speed to 20 m/s doubles thinking distance to 14 m and roughly quadruples braking distance. Estimate by choosing typical speeds, a reaction time and a deceleration, then compare results across the range to show the rapid increase at higher speed.
What earns the marks
- Defines stopping distance as thinking distance plus braking distance.
- Explains that thinking distance increases in proportion to speed for a fixed reaction time.
- Explains that braking distance increases with the square of speed.
- Estimates stopping distances at several typical speeds and shows they rise steeply as speed increases.
Common mistakes and how to put them right
Assumes stopping distance doubles when speed doubles.
Put it right: Recognise that braking distance rises with the square of speed.
Ignores reaction time when estimating thinking distance.
Put it right: Multiply speed by reaction time.
Adds only braking distance and forgets thinking distance.
Put it right: Total both parts for stopping distance.
Exam tips
- State the reaction time and deceleration you assume before estimating.
- Compare at least two speeds to show how stopping distance changes across the range.
- Keep units consistent, converting speeds to metres per second where needed.
Try the lesson
The start of the Topic 2 – Motion and forces: 2.32P Estimate how the distance required for a road vehicle to stop in an emergency varies over a range of typical speeds lesson, made from checked teaching notes for this specification point.
Have a go first
A car's braking distance at 20 m/s is 20 m. A second car of the same type travels at 40 m/s. Using the idea that braking distance increases with the square of the speed, estimate the second car's braking distance.
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Topic 2 – Motion and forces: 2.32P Estimate how the distance required for a road vehicle to stop in an emergency varies over a range of typical speeds
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge