A delivery van travels along a straight road at 20 m/s. The driver sees an obstacle ahead and reacts before applying the brakes. The van then decelerates uniformly and comes to a complete stop. Explain how the concepts of thinking distance, braking distance, and stopping distance are related to this journey, and describe one factor that would increase the thinking distance in this situation.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A delivery van travels along a straight road at 20 m/s. The driver sees an obstacle ahead and reacts before applying the brakes. The van then decelerates uniformly and comes to a complete stop.
Model answer (5 marks)
Thinking distance is the distance the van travels while the driver is reacting to the obstacle, before the brakes are applied.
Braking distance is the distance the van travels after the brakes are applied until it comes to a complete stop.
Stopping distance is the total distance travelled from the moment the driver sees the obstacle until the van stops, so it equals thinking distance plus braking distance.
One factor that would increase the thinking distance is if the driver is tired. A tired driver has a longer reaction time, so the van travels a greater distance before the brakes are applied, increasing the thinking distance.
Braking distance is the distance the van travels after the brakes are applied until it comes to a complete stop.
Stopping distance is the total distance travelled from the moment the driver sees the obstacle until the van stops, so it equals thinking distance plus braking distance.
One factor that would increase the thinking distance is if the driver is tired. A tired driver has a longer reaction time, so the van travels a greater distance before the brakes are applied, increasing the thinking distance.
Examiner tips
- Define each distance clearly; show the relationship stopping = thinking + braking. Give a specific factor (e.g. tired, distracted, drunk) and explain it increases reaction time. Use correct terminology and UK spelling.
- common_mistakes
- :
- Confusing braking distance with stopping distance. Failing to link the factor to a longer reaction time. Using vague factors like "bad weather" without explaining the effect on reaction time.
Mark scheme (5 marks)
- Thinking distance is the distance the van travels during the driver's reaction time (before brakes are applied)
- Braking distance is the distance the van travels after the brakes are applied until it stops
- Stopping distance = thinking distance + braking distance
- One factor that increases thinking distance correctly identified (e.g. driver is tired / distracted / under the influence of alcohol or drugs)
- Correct explanation of why the identified factor increases thinking distance — links factor to a longer reaction time, meaning the van travels further before braking begins
Key terms in this question
thinking distance · braking distance · stopping distance
Related
- All Edexcel A-Level Physics (9PH0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More Motion questions
- A skateboarder starts from rest at the top of a slope. She rolls down the slope,…
- A cyclist is travelling along a straight, flat road at a constant velocity of 12…
- A sprinter starts from rest and accelerates along a straight track. After 4 seco…
- A car travels along a straight road. It starts from rest and accelerates uniform…