AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
A driver’s reaction time can be affected by tiredness, drugs and alcohol.…
Full specification wording
Reaction time: A driver’s reaction time can be affected by tiredness, drugs and alcohol. Distractions may also affect a driver’s ability to react.
Tiredness, alcohol, other drugs and distractions such as a phone all lengthen a driver's reaction time.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 2 of 2
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Tiredness, alcohol, other drugs and distractions such as a phone all lengthen a driver's reaction time. The mechanism is the same in each case: the brain takes longer to process the hazard and send the signal to the muscles, so more time passes before the brakes are applied. Since thinking distance = speed × reaction time, the thinking distance grows, and because stopping distance is thinking plus braking distance, the whole stop lengthens. The brakes, tyres and road are untouched, so the braking distance itself is unchanged. Data on alcohol shows two things worth quoting: the mean reaction time rises after drinking, and the increase is not the same for every person. A phone call or a conversation acts in exactly the same way, adding time before the driver's foot reaches the brake pedal.
What earns the marks
- Naming a factor: tiredness, alcohol, another drug or a distraction.
- Stating that the reaction time increases.
- Linking that to a longer thinking distance.
- Concluding that the stopping distance increases.
- A data conclusion such as the mean reaction time increases after alcohol but not by the same amount for everyone.
Common mistakes and how to put them right
Listing wet or icy roads, which lengthen the braking distance rather than the reaction time.
Saying alcohol increases the braking distance.
Writing that the driver is 'slower' without naming reaction time or thinking distance.
Claiming every person's reaction time rises by the same amount after drinking, which the data does not support.
Exam tips
- Check whether the question asks about thinking or braking distance before you choose your factors.
- When a graph of individual results is given, comment on the spread as well as the mean.
- Say 'increases the reaction time' explicitly; naming the factor alone is usually only one of the marks.
Try the lesson
The start of the Reaction time: A driver’s reaction time can be affected by tiredness, drugs and alcohol. Distractions may also affect a driver’s ability to react. lesson, made from checked teaching notes for this specification point.
Have a go first
Which of these is a distraction that may increase a driver’s reaction time?
Listen
Tiredness, alcohol, other drugs and distractions such as a phone all lengthen a driver's reaction time. The mechanism is the same in each case: the brain takes longer to process the hazard and send the signal to the muscles, so more time passes before the brakes are applied. Since thinking distance = speed × reaction time, the thinking distance grows, and because stopping distance is thinking plus braking distance, the whole stop lengthens. The brakes, tyres and road are untouched, so the braking distance itself is unchanged. Data on alcohol shows two things worth quoting: the mean reaction time rises after drinking, and the increase is not the same for every person. A phone call or a conversation acts in exactly the same way, adding time before the driver's foot reaches the brake pedal. A strong answer earns marks for these points. naming a factor: tiredness, alcohol, another drug or a distraction. stating that the reaction time increases. linking that to a longer thinking distance. concluding that the stopping distance increases. Exam tip: Check whether the question asks about thinking or braking distance before you choose your factors.
Key words
Say what each word means before you turn the card.
tiredness
Try answering aloud or in your head before turning the card.
alcohol and drugs
Try answering aloud or in your head before turning the card.
distractions
Try answering aloud or in your head before turning the card.
thinking distance
Try answering aloud or in your head before turning the card.
See every definition
- tiredness
- One of the factors that can affect a driver's reaction time, making the brain take longer to process the hazard and send the signal to the muscles.
- alcohol and drugs
- Factors that can affect a driver's reaction time; data shows the mean reaction time rises after drinking but not by the same amount for everyone.
- distractions
- Things such as a phone that may affect a driver's ability to react, adding time before the driver's foot reaches the brake pedal.
- thinking distance
- Equal to speed multiplied by reaction time, so it grows when reaction time increases.
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