AQA GCSE Physics

Revision Notes

5.8.4 Factors Affecting Thinking Distance & Reaction Time

Factors Affecting Reaction Time

  • Human reaction time can depend on a number of factors. It is increased by:
    • Tiredness
    • Distractions (e.g. using a mobile phone)
    • Intoxication (i.e. consumption of alcohol or drugs)
  • Since these factors can affect the reaction time of a human, they directly affect the thinking distance when travelling in a car
    • The main factor that affects the thinking distance is the car’s speed
    • Additional factors, like those given above, can affect the thinking distance

Worked Example

The graph below shows how the thinking distance of a driver depends on the speed of the car.

WE Thinking distance question graph, downloadable IGCSE & GCSE Physics revision notes

(a) Describe the connection between thinking distance and speed.

(b) Some people drive when they are tired, despite warnings against doing so. Draw a new line on the graph to show how thinking distance varies with speed for a tired driver.

Part (a)

Step 1: Check if the line is straight and if it goes through the origin

    • The graph shows a straight line through the origin
    • Therefore, the thinking distance is directly proportional to the speed of the car

Part (b)

Step 1: Recall the factors which affect the thinking distance

    • Three additional factors affect the thinking distance, because they affect human reaction time:
      • Tiredness
      • Distractions
      • Intoxication
    • Hence, a tired driver’s reaction time is greater (i.e. it takes longer for them to react)

Step 2: Draw a line that shows greater thinking distance for the same speed

    • At the same speed, a tired driver’s thinking distance will be greater than a driver who is alert
    • This means a line should be drawn with a steeper gradient, as shown below:

WE Thinking distance solution graph, downloadable IGCSE & GCSE Physics revision notes

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Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.
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