AQA GCSE Combined Science: Trilogy Physics Paper 2 (Higher), June 2025: Question 2
12 marks · Standard Demand difficulty · Extended Answer
Calculate the deceleration of a stopping car, explain factors affecting stopping distance and safety, and explain the effect of speed on brake overheating.
Practise this questionQuestion
Question text
02 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.
02.1 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]
7Deceleration = m/s2
02.2 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
02.3 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
Question 2
AO /
Question Answers Extra information Mark
Spec. Ref.
02.1 (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/P1/2H –
AO /
Question Answers Mark
Spec. Ref.
02.2 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 thinking / 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
8 • decreased speed decreases the chance of a collision
• 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.TRILOGY – 8464/P/2H –
AO /
Spec. Ref.
02.3 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 2 12
How to answer it
Forces, Deceleration & Stopping Distances
Key Skills & Knowledge Assessed:
- Equation recall & calculation: Applying the uniform acceleration equation ( v² - u² = 2as ) to determine deceleration.
- Stopping distance components: Understanding the clear physical differences between thinking distance, braking distance, and total stopping distance.
- 6-mark logical structuring: Linking vehicle condition (tyres/brakes) and road speed to driver reaction, friction, and passenger safety.
- Work done & thermal energy transfers: Explaining brake overheating using work done against friction ( W = F × s ) and kinetic energy conversion.
Question 02.1: Calculating Deceleration
Part (a) • 3 Marks • Physics Equation Sheet
📐 Step-by-Step Calculation
• Initial velocity, u = 18 m/s
• Final velocity, v = 0 m/s (the car stops)
• Distance, s = 24 m
• Formula: v² - u² = 2as
0² - 18² = 2 × a × 24
-324 = 48 × a (or 18² = 2 × a × 24 )
a = -324 / 48 = -18² / (2 × 24)
Deceleration = 6.75 m/s² (or -6.75 m/s² ; 6.8 m/s² is also accepted).
🧠 Exam Technique
Deceleration vs. Acceleration: Deceleration is negative acceleration. The mark scheme accepts either 6.75 or -6.75, but stating a positive value for "deceleration" is standard physical convention.
❌ Common Errors
- Forgetting to square the speed: using 18 instead of 18² (324) .
- Incorrect formula choice: trying to use a = (v - u) / t when time ( t ) is not given!
Question 02.2: Factors Affecting Stopping Distance & Safety
Part (b) • 6 Marks Extended Response • Level of Response
🧠 Examiner Strategy for Level 3 (5–6 Marks)
To reach Level 3, your answer must be logically linked and cover all five key themes prompted in the question:
Brakes & Tyres → Speed → Thinking Distance → Braking Distance → Safety
✅ Model 6-Mark Structure
1. Thinking Distance:
- Condition of brakes and tyres has no effect on thinking distance.
- Speed does not change driver reaction time, but a reduced speed reduces thinking distance (as distance = speed × reaction time ).
2. Braking Distance:
- Worn tyres/brakes reduce friction between tyres and the road surface, which increases braking distance.
- Reduced speed significantly decreases braking distance (because kinetic energy is proportional to speed² ).
3. Road User Safety:
- Stopping distance = thinking distance + braking distance .
- Reducing speed decreases overall stopping distance, which reduces the chance of collision and loss of vehicle control.
- Lower speed also reduces the severity of injuries if a collision does occur.
❌ Common Misconceptions
- Thinking Distance Trap: Many students claim that "poor brakes increase thinking distance". Incorrect! The car hasn't even begun braking during the driver's reaction time.
- Speed vs. Reaction Time: "Lower speed improves reaction time." Incorrect! Speed changes the distance you travel while reacting, not your brain's processing speed.
- Missing the Safety link: Listing points about stopping distance without explicitly stating the outcome on safety (e.g. chance of crashes, injury severity).
Question 02.3: Kinetic Energy, Work Done & Brake Overheating
Part (c) • 3 Marks • Explanation & Energy Stores
✅ Marking Points Breakdown
- Mark 1 Energy / Force comparison:
The faster car has more kinetic energy (or requires a greater braking/frictional force to stop over the same distance). - Mark 2 Work done / Energy transfer:
Therefore, more work is done by the brakes to stop the car (or more energy is transferred to the thermal store of the brakes). - Mark 3 Conclusion on overheating:
This causes a larger temperature increase, so the risk of the brakes overheating is greater for the faster car.
💡 Key Physics Concepts
Work Done Against Friction:
Work Done = Braking Force × Braking Distance
To bring a car to a stop, all kinetic energy ( ½mv² ) must be transferred into thermal energy via work done by the brakes.
Since braking distance was kept constant for both cars:
- Higher speed = much higher initial kinetic energy.
- All this extra energy is dissipated as heat in the exact same distance and in less time.
- Result: Rapid heat build-up leading to brake fade/overheating.
🧠 Examiner Insight
Mark 3 is directly dependent on earning Mark 1 or Mark 2. Simply stating "the brakes will overheat" without explaining the link to greater kinetic energy or work done scores 0 marks.
Topics
Physics · P5: Forces
Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Physics Paper 2 (Higher), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.