5.20 Stopping distance and reaction time
9 exam questions worth 20 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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Which of these increases only the thinking distance?
Choose one answer.
Correct Not quite: the answer is Tiredness of the driver
Mark scheme
C: Tiredness of the driver
Model answer
Tiredness of the driver (C).
State the equation that links stopping distance, thinking distance and braking distance.
Mark scheme
stopping distance = thinking distance + braking distance
Model answer
Stopping distance = thinking distance + braking distance.
A driver's reaction time is 0.7 s and the car is travelling at 25 m/s. Calculate the thinking distance.
Mark scheme
distance = speed × time = 25 × 0.7 (1); 17.5 m (1)
Model answer
Thinking distance = 25 × 0.7 = 17.5 m.
A car has a thinking distance of 12 m and a braking distance of 30 m. Calculate the stopping distance.
Mark scheme
12 + 30 (1); 42 m (1)
Model answer
Stopping distance = 12 + 30 = 42 m.
State the typical range of human reaction times.
Mark scheme
0.2 s to 0.9 s
Model answer
Between 0.2 s and 0.9 s.
Give three factors that can increase a driver's reaction time.
Mark scheme
any three from: tiredness (1); alcohol (1); drugs / some medicines (1); distractions such as a mobile phone / passengers (1); age (1)
Model answer
Tiredness, alcohol and being distracted by a mobile phone.
Explain what happens to the thinking distance when the speed of the car doubles and the driver's reaction time stays the same.
Mark scheme
thinking distance doubles (1); distance = speed × time and time is the same (so distance is directly proportional to speed) (1)
Model answer
It doubles, because the thinking distance is the speed multiplied by the reaction time.
A student catches a ruler after it has fallen 20 cm (0.20 m). Calculate their reaction time. (g = 9.8 m/s²)
Mark scheme
t = √(2d ÷ g) (1); √(2 × 0.20 ÷ 9.8) (1); 0.20 s (1)
Model answer
t = √(2 × 0.20 / 9.8) = √0.0408 = 0.20 s.
Describe how you could use a ruler to investigate whether using a mobile phone affects reaction time. Include how to make the test fair.
Mark scheme
partner drops the ruler and you catch it (1); read the distance fallen and calculate the reaction time (1); repeat with and without the phone (the independent variable) (1); keep other variables the same, e.g. the same person, the same hand, the same ruler (1); repeat several times and calculate a mean (1)
Model answer
A partner drops a ruler without warning and the student catches it, and the distance fallen is used to calculate the reaction time. The test is done with and without a phone conversation. The same person, hand and ruler are used, and each test is repeated several times to find a mean.
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