FRICTION AND BRAKING
4 marks · NormalA van is travelling along a dry road at 40 mph. The thinking distance is 12 m and the braking distance is 24 m.
Calculate the total stopping distance for the van.
If the driver was distracted, the reaction time would increase. Explain what would happen to the stopping distance.
The braking distance would remain the same. Explain why.
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(a) 36 m
(b) Stopping distance would increase because a longer reaction time increases thinking distance, so the van will travel further before braking begins.
(c) Because braking distance depends only on speed, road and tyres, not on reaction time.
Common mistakes: Confusing thinking and braking distances.
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Marking points
A1 (a) · 1 mark · Correct addition: 12 m + 24 m = 36 m
B1 (b) · 2 marks · Mentions and explains that increased reaction increases thinking distance and thus increases overall stopping distance.
B1 (c) · 1 mark · States braking distance is unaffected as it only depends on speed, vehicle, and road conditions.
Worked solution
a) Total stopping distance = thinking distance + braking distance = 12 m + 24 m = 36 m.
b) Stopping distance increases because a longer reaction time means the van travels further before braking starts (thinking distance increases).
c) Braking distance depends only on conditions and speed, not driver's reaction.