Question Constellation Sign up for free AQA · GCSE · Physics · Higher
Alcohol, Reaction Time and Stopping Distance
It is illegal for train drivers to drink alcohol before driving a train.
Explain how drinking alcohol would affect the stopping distance of a train.
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Marking points
- 1 States that stopping distance comprises thinking distance and braking distance.
- 2 States that alcohol increases reaction time.
- 3 Links the longer reaction time to greater thinking distance and hence greater stopping distance.
Full-mark answer
Stopping distance is the thinking distance plus the braking distance. Alcohol increases the driver's reaction time, so the train travels farther during the thinking time. The thinking distance and therefore the total stopping distance increase.
Why this answer loses marks
Alcohol makes the train’s brakes less effective.
The credited route is through increased reaction time and thinking distance, not a change to the mechanical braking force.