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GCSE Questions: Forces

Q24. The driver of a vehicle sees a hazard on the road.

(a) The driver uses the brakes to stop the vehicle. Explain the factors that affect the distance needed to stop a vehicle in an emergency.

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:

Relevant points (reasons / causes) are identified, given in detail and logically linked to form a clear account.

The answer would list at least three factors

with

at least two linked but different explanations
5 - 6 marks
Level 2:

Relevant points (reasons / causes) are identified, and there are attempts at logical linking but the resulting account is not fully clear.

The answer would list at least three factors with one linked explanation

or

two factors with two linked but different explanations.
3 - 4 marks
Level 1:

Points are identified and stated simply, but their relevance is not clear and there is no attempt at logical linking.

The answer would list factors only

or

have only one factor with one linked explanation
1 - 2 marks
Level 0:

No relevant information
0 marks

 

Indicative content:

reaction time explained in terms of longer reaction times increasing thinking distance (from a given speed) because of:

• taking drugs

• drinking alcohol

• tiredness

• age

• distractions

speed the vehicle is travelling at - explained in terms of the faster the vehicle the greater the distance travelled in the driver's reaction time (or converse) OR explained in terms of increased speed increases KE so increases work done to stop the vehicle,

the efficiency of the braking system on the car explained in terms of effect on braking force (applied to the wheels) or reduced friction - which is affected by:

• condition of the tyres

• condition of road surface

• wet/icy roads explained in terms of condition of tyres and road surface (including weather considerations) affecting friction (between tyres and road)

• condition of brakes

mass / weight of vehicle explained in terms of deceleration force or kinetic energy or change in momentum.

[6 marks]

(b) Write down the equation which links distance, force and work done.

Work done = farce x distance moved in the direction of the application of the force.

W = Fs

[1 mark]

(c) The work done by the braking force to stop a vehicle was 900,000 J.

The braking force was 60,000 N

Calculate the braking distance of the vehicle.

W = Fs

s = W/F

s = 900,000/60,000

s = 15 m

[3 marks]

(d) The greater the braking force, the greater the deceleration of a vehicle. Explain the possible dangers caused by a vehicle having a large deceleration when it is braking.

There is a danger of the brakes overheating, or the brakes locking causing a loss of control of the vehicle or a skid.

Any answer referring to the effects on passengers or possible accidents was ignored by the examiners - they wanted you to discuss what happens to the vehicle.

[2 marks]

[12 Marks TOTAL]