AQA GCSE Combined Science: Trilogy Physics Paper 2 (Foundation), June 2025: Question 7

12 marks · Standard Demand difficulty · Extended Answer

Calculate the deceleration of a stopping car, explain how speed and vehicle condition affect road user safety, and explain the effect of higher speed on brake overheating.

Practise this question

Question

Question 7 contains three sub-questions about car braking and stopping distances. Sub-question 7.1 gives an initial velocity of 18 m/s, final velocity of 0 m/s, and distance of 24 m, asking to calculate the constant deceleration using the Physics Equations Sheet for 3 marks. Sub-question 7.2 is a 6-mark extended response asking to explain how road user safety is affected by the condition of brakes and tyres and reduced speed, with reference to thinking distance and braking distance. Sub-question 7.3 describes two identical cars travelling at different speeds that stop over the same braking distance, asking for a 3-mark explanation of how braking from a greater speed affects the risk of brake overheating.
Question text

07 The stopping distance of a car is affected by the condition of the brakes and tyres.

A car is being driven around a corner when the driver sees some roadworks.

07.1 The driver applies the brakes when the car is 24 m away from the roadworks.

The velocity of the car changes from 18 m/s to 0 m/s.

Calculate the constant deceleration needed to stop the car in a distance of 24 m.

Use the Physics Equations Sheet.

[3 marks]

31Deceleration = m/s2

07.2 As a safety measure, the speed limit on the road was reduced.

Explain how the safety of road users is affected by:

• the condition of the brakes and tyres

• reduced speed.

You should refer to thinking distance and braking distance.

[6 marks]

Extra space

07.3 Two identical cars were driven along a straight, level road.

One car had a greater speed than the other car.

The driver of each car applied the brakes until the cars stopped.

Both cars travelled the same distance while braking.

Explain how braking from a greater speed affected the risk of the brakes overheating.

[3 marks]

Mark scheme

Show the mark scheme Mark scheme for Question 7. 07.1 gives 1 mark for substitution into (0^2 -) 18^2 = 2 * a * 24, 1 mark for rearrangement a = (-)18^2 / (2 * 24), and 1 mark for the answer (-)6.75 m/s^2 (allow 6.8). 07.2 uses a 3-level response scheme (5-6, 3-4, 1-2 marks) with indicative content covering thinking distance, braking distance, and overall safety/stopping distance. 07.3 awards 3 marks: 1 mark for greater frictional braking force or faster car has more kinetic energy, 1 mark for more work done (or more energy transferred) by the brakes to stop the faster car, and 1 mark for greater risk of brakes overheating.

Question 7

AO /

Question Answers Extra information Mark

Spec. Ref.

07.1 (02–) 182 = 2 × a × 24 allow 182 = 2 × a × 24 1 AO2

6.5.4.1.5

(–)18

a =

2 × 24

a = (–) 6.75 (m/s2) – allow (–) 6.8 (m/s2) – 8464/P1/2F –

AO /

Question Answers Mark

Spec. Ref.

07.2 Level 3: Relevant points (reasons / causes) are identified, given in 5–6 AO2

detail and logically linked to form a clear account.

Level 2: Relevant points (reasons / causes) are identified, and 3–4 AO1

there are attempts at logical linking. The resulting account is not

fully clear.

Level 1: Points are identified and stated simply, but their relevance 1–2 AO1

is not clear and there is no attempt at logical linking.

6.5.4.2.2

No relevant content 0 6.5.4.3.1

6.5.4.3.3

6.5.4.3.4

Indicative Content

Thinking distance

• condition of brakes and tyres does not affect thinking distance

• speed does not affect reaction time

• decreased speed decreases thinking distance

Braking distance

• condition of tyres affects friction between tyres and road

• poor condition of tyres and brakes increases braking distance

• decreased speed decreases braking distance

Safety

• stopping distance = thinking distance + braking distance

• poor condition of brakes and tyres increases stopping distance

• decreased speed decreases stopping distance

• decreased speed decreases the chance of the driver losing

control of the vehicle

• decreased speed decreases the chance of a collision 17

• decreased speed decreases the risk of injury during a collision

for Level 3, answers must include references to brakes / tyres,

speed, thinking distance, braking distance, and safety.– – 8464/P/2F –

AO /

Spec. Ref.

07.3 frictional / braking force is 1 AO1

greater (for the faster car)

or

the faster car has more kinetic

energy

(so) more work done (by the allow so more energy is 1 AO3

brakes to stop the faster car) transferred (by the brakes to

stop the faster car)

ignore more heating

(so) the risk of the brakes allow (at greater speed) there is 1 AO3

overheating is greater (for the a risk of overheating 6.5.4.3.4

fast car)

MP3 dependent on MP1 or MP2

Total Question 7 12

How to answer it

Forces, Motion & Stopping Distances

📌 What this question tests

This question assesses key concepts from AQA GCSE Physics: Forces and Motion. You need to apply kinematic equations with constant acceleration ( v² - u² = 2as ), logically analyze the factors influencing thinking distance, braking distance, and overall road safety in an extended 6-mark response, and explain how kinetic energy and work done cause brake heating.

Question 07.1 • 3 Marks

Calculating Deceleration

Using kinematic equations for a stopping vehicle

📐 Step-by-Step Calculation

  1. Identify the given values:
    Initial velocity ( u ) = 18 m/s
    Final velocity ( v ) = 0 m/s (stopped)
    Distance ( s ) = 24 m
    Deceleration ( a ) = ?
  2. Select the correct formula:
    v² - u² = 2 × a × s
  3. Substitute the values:
    0² - 18² = 2 × a × 24
    -324 = 48a
    awarded [1 mark]
  4. Rearrange to solve for acceleration (a):
    a = -324 / 48
    awarded [1 mark]
  5. State the final value:
    a = 6.75 m/s² (or -6.75 m/s²; 6.8 m/s² is also accepted)
    awarded [1 mark]

✅ Correct Answer

6.75 m/s² (or 6.8 m/s²)

Note: The question asks for deceleration, so a positive or negative sign is accepted by the mark scheme.

❌ Common Errors

  • Wrong equation: Trying to use a = (v - u) / t when time ( t ) is not given. Always check your physics equations sheet for an equation matching the variables you have.
  • Squaring errors: Forgetting to square the velocity, writing 18 instead of 18² = 324 .
  • Division order: Dividing 48 / 324 instead of 324 / 48 .
Question 07.2 • 6 Marks

Extended Response: Speed, Condition of Car, and Road Safety

Explaining effects on thinking distance, braking distance, and overall safety

💡 Core Knowledge

Stopping Distance = Thinking Distance + Braking Distance

  • Thinking Distance: The distance travelled while the driver reacts. Affected by speed and reaction time (tiredness, alcohol, distractions).
  • Braking Distance: The distance travelled under the braking force. Affected by speed, road conditions (ice/wet), and vehicle condition (worn tyres, worn brakes).

🧠 Level 3 Marking Criteria Checklist

To reach Level 3 (5–6 marks), your answer must be a clear, logically structured account that explicitly mentions:

  • Tyre and brake conditions
  • Reduced speed
  • Thinking distance
  • Braking distance
  • Safety implications

✅ Model Answer (Level 3: Full 6 Marks)

1. Thinking Distance:

  • The condition of the brakes and tyres has no effect on thinking distance or reaction time.
  • A reduced speed does not change the driver's reaction time, but because the vehicle is travelling fewer metres per second ( distance = speed × time ), a lower speed decreases thinking distance.

2. Braking Distance:

  • Worn tyres reduce friction/grip between the tyre and the road surface, and worn brakes apply less braking force. Therefore, poor brakes and tyres increase braking distance.
  • Reducing speed significantly decreases braking distance because the car has much less kinetic energy to lose.

3. Safety of Road Users:

  • Since stopping distance = thinking distance + braking distance , reducing the speed decreases overall stopping distance, while poor brakes/tyres increase it.
  • A reduced speed lowers the likelihood of collisions, lowers the chance of losing control, and reduces the severity of injuries if a collision does occur because less kinetic energy is transferred upon impact.

❌ Common Misconceptions to Avoid

  • Confusing the two distances: Saying that worn tyres increase thinking distance. Drivers do not think slower because their tyres are bald! Tyres only affect braking distance.
  • Confusing reaction time and speed: Stating that speed changes a driver's reaction time. Speed changes the distance covered during the reaction time, not the reaction time itself.
  • Omitting safety: Forgetting to mention the actual impact on safety (e.g. less risk of collision, reduced severity of injury).
Question 07.3 • 3 Marks

Kinetic Energy, Work Done, and Overheating Brakes

Why braking from higher speed increases brake temperature

💡 Physics Principles at Play

  • Kinetic Energy: Ek = ½mv² . Because kinetic energy depends on speed squared, a faster car has significantly more kinetic energy.
  • Work Done: Work Done = Braking Force × Braking Distance . To stop a car, all kinetic energy must be transferred into thermal energy via work done by the friction between the brake pads and discs.

✅ Mark Scheme Breakdown

  1. Point 1 (Energy/Force): The faster car has more kinetic energy (OR the braking/frictional force is greater to stop in the same distance).
    Awarded [1 mark]
  2. Point 2 (Work Done / Energy Transfer): Therefore, more work is done by the brakes (OR more energy is transferred into the thermal store of the brakes).
    Awarded [1 mark]
  3. Point 3 (Conclusion): This causes a greater temperature rise, so the risk of the brakes overheating is increased.
    Awarded [1 mark] (dependent on Point 1 or 2)

❌ Examiner Trap

Do not simply write "there is more heat" or "more friction means it gets hot". Examiners specifically look for the physics terms more kinetic energy and more work done / energy transferred. Note that Point 3 cannot be awarded unless you successfully link it to either the higher kinetic energy or the greater work done.

Topics

Physics · P5: Forces

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Physics Paper 2 (Foundation), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.