GCSE Questions: Forces
Q25. The table below shows thinking, braking and stopping distances for the same car travelling at different speeds.
Speed (m/s) |
Thinking distance (m) |
Braking distance (m) |
Stopping distance (m) |
8 |
6 |
6 |
12 |
16 |
12 |
24 |
36 |
32 |
24 |
96 |
120 |
(a) Describe how the thinking distance changes when the speed doubles.
Use data from the table in your answer.
Thinking distance doubles when speed doubles. (For example it goes from 6m to 12 m when speed changes from 8 m/s to 16 m/s). This indicates they are directly proportional to each other. ![](../../../graphics/symbols/nuclides/ticksmall.png)
[1 mark]
(b) Calculate the reaction time (in seconds) of the person driving the car.
(Reaction) time = (Thinking) distance ÷ Speed ![](../../../graphics/symbols/nuclides/ticksmall.png)
6 ÷ 8 or 12 ÷ 16 or 24 ÷ 32 ![](../../../graphics/symbols/nuclides/ticksmall.png)
= 0.75 s ![](../../../graphics/symbols/nuclides/ticksmall.png)
[3 marks]
(c) Explain why the stopping distances are different for each speed shown in the above table.
![](../../../graphics/Bulletpoints/FuzzleGREEN.png)
5 - 6 marks |
3 - 4 marks |
1 - 2 marks |
Level 0: |
No relevant information |
0 marks |
Examples of physics points that should be made in the response:
Demonstrates knowledge and understanding of thinking, braking and stopping distance:
- Thinking distance is the distance the car travels while the driver reacts
- Braking distance is the distance travelled while the brakes are applied
- Stopping distance is thinking distance + braking distance
Applies knowledge and understanding of thinking, braking and stopping distance in relation to the details in the table
- Increasing the speed, increases the thinking distance
- Increasing the speed, increases the braking distance
- Increasing the speed, increases the stopping distance
Analyses information to make judgements and draw detailed conclusions from table
- Thinking distance is directly proportional to the speed
- When speed doubles, thinking distance doubles
- Braking distance is proportional to speed2
- When speed doubles, braking distance quadruples
[6 marks]
[10 Marks TOTAL]