GCSE Questions: Forces

Q25. The table below shows thinking, braking and stopping distances for the same car travelling at different speeds.

 

(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.

[1 mark]

(b) Calculate the reaction time (in seconds) of the person driving the car.

(Reaction) time = (Thinking) distance ÷ Speed

6 ÷ 8 or 12 ÷ 16 or 24 ÷ 32

= 0.75 s

[3 marks]

(c) Explain why the stopping distances are different for each speed shown in the above table.

This type of question is marked in two ways:

- the examiner looks for relevant points

- but also for a logical sequence...

It is not just a 'tick fest' - but a marker does look to see how many relevant points you have made, then considers how you have strung them together to put your answer into a 'level'

Level 3:	Explains quantitatively why the stopping distances are different for each speed in the table in terms of braking distance and thinking distance. There is a well-developed line of reasoning which is clear and logically structured. The information presented is relevant and substantiated.	5 - 6 marks
Level 2:	Explains qualitatively why the stopping distances are different for each speed in the table in terms of braking distance or thinking distance increasing with speed from the table There is a line of reasoning presented with some structure. The information presented is relevant and supported by some evidence.	3 - 4 marks
Level 1:	States basic ideas about thinking distance /braking distance/stopping distance OR Identifies variation of thinking distance/braking distance/stopping distance with speed There is an attempt at a logical structure with a line of reasoning. The information is in the most part relevant.	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]