AQA GCSE Physics Physics Paper 2 (Higher), June 2025: Question 6

13 marks · Standard Demand difficulty · Short Answer

Compare car accelerations, explain how air bags reduce injury, calculate braking force using kinematics or work-energy, and explain the effects of large deceleration.

Practise this question

Question

Question 6 consists of five parts: 06.1 asks how the maximum acceleration of car X compares with car Y given identical cars except car X has greater mass (1 mark). 06.2 asks to explain how air bags reduce the chance of injury to the driver when a car stops suddenly (3 marks). 06.3 provides car X's mass of 1400 kg travelling at 18 m/s, stopping with constant deceleration in 24 m, and asks to calculate the resultant force using the equations sheet (5 marks). 06.4 asks to explain why braking causes an increase in brake temperature (2 marks). 06.5 asks for two possible risks of a large deceleration (2 marks).

Mark scheme

Show the mark scheme Mark scheme for Question 6 detailing answers: 06.1 awards 1 mark for stating car X has a smaller maximum acceleration. 06.2 awards 3 marks for increasing stopping time, reducing the rate of change of momentum (or deceleration), and reducing force on the driver. 06.3 gives 5 marks for substituting into v^2 - u^2 = 2as to find a = -6.75 m/s^2 and calculating F = ma = 9450 N (or alternative methods using kinetic energy/work done or average velocity). 06.4 awards 2 marks for work done by friction transferring kinetic energy to thermal energy. 06.5 awards 2 marks for brakes overheating and driver losing control of the car.

How to answer it

Forces, Motion, and Vehicle Safety

What this question tests

This question evaluates your understanding of Newton's Laws of Motion, vehicle safety devices, multi-step kinematic calculations, and thermal energy dissipation during braking:

  • Newton’s Second Law: The relationship between resultant force, mass, and acceleration ( F = ma ).
  • Car Safety & Momentum: How airbags reduce impact forces by increasing impact time ( F = Δp / Δt ).
  • Multi-Step Problem Solving: Selecting appropriate equations ( v² - u² = 2as and F = ma or work done W = Fs ) to determine braking force.
  • Energy Transfers & Road Safety: Work done by friction, transfer from kinetic to thermal energy, and consequences of large decelerations.
Question 06.1 • 1 Mark

Comparing Acceleration of Different Masses

Relationship between mass and acceleration for identical engine forces

✅ Correct Answer

Car X has a smaller maximum acceleration (than car Y).

1 Mark: Explicitly state car X has smaller / lower acceleration.

💡 Key Knowledge

Rearranging Newton's Second Law: a = F / m

Since the cars are identical except for mass, the maximum forward force F generated is the same. Acceleration is inversely proportional to mass: greater mass means smaller acceleration.

Question 06.2 • 3 Marks

How Airbags Prevent Injury

Explaining safety devices using momentum and impact forces

✅ Correct Answer (3-Point Structure)

  1. The airbag increases the time taken for the driver to stop. [1]
  2. This decreases the rate of change of momentum (or reduces the driver's deceleration). [1]
  3. Therefore, the force exerted on the driver is reduced. [1]
Note: Writing "the momentum change is the same but over a longer time" satisfies marking points 1 and 2 together.

🧠 Exam Technique: The Golden Rule of Safety Devices

Whenever an exam asks about seatbelts, airbags, crumple zones, or helmets, always follow this exact 3-step sequence:

Time increases → Rate of change of momentum decreases → Force decreases ( F = Δp / Δt ).

❌ Common Errors

  • Saying the airbag "absorbs the force" or "reduces the momentum change" (the driver still comes to a complete stop, so total change in momentum is unchanged!).
  • Failing to mention time and jumping straight to "it softens the blow".
Question 06.3 • 5 Marks

Calculating the Braking Force

Multi-step calculation using uniform acceleration and force equations

📐 Method 1: Using Kinematics & Newton's 2nd Law (Recommended)

Step 1: Identify the known values
m = 1400 kg , u = 18 m/s , v = 0 m/s , s = 24 m

Step 2: Choose equation to find acceleration (a)
v² - u² = 2as
0² - 18² = 2 × a × 24 [1 mark]
-324 = 48a [1 mark]
a = -324 / 48 = -6.75 m/s² [1 mark]

Step 3: Calculate resultant force (F)
F = m × a
F = 1400 × (-)6.75 [1 mark]
Resultant force = 9450 N [1 mark]

📐 Method 2: Using Work Done & Kinetic Energy

Step 1: Calculate initial Kinetic Energy
Ek = ½mv²
Ek = ½ × 1400 × 18² [1 mark]
Ek = 226 800 J [1 mark]

Step 2: Relate Work Done to kinetic energy loss
Work Done = Braking Force × distance ( W = F × s )
226 800 = F × 24 [1 mark]
F = 226 800 / 24 [1 mark]

Step 3: State final value
Resultant force = 9450 N [1 mark]

❌ Common Calculation Traps

  • Forgetting to square: Forgetting to square 18 (calculating 18 × 2 instead of 18² = 324 ).
  • Sign confusion: Acceleration is negative (-6.75 m/s²) because it is deceleration. The resultant force acts opposite to the direction of motion. Either 9450 N or -9450 N is awarded full marks.
Question 06.4 • 2 Marks

Temperature Rise During Braking

Work done and mechanical energy dissipation

✅ Correct Answer

  • Work is done by friction between the brake pads and the wheels. [1]
  • This causes (kinetic) energy of the car to be transferred to thermal energy in the brakes. [1]

❌ Examiner Warning

Do not simply write "because of friction". The mark scheme specifically states ignore friction alone. You must state that work is done by friction to earn the first mark.

Question 06.5 • 2 Marks

Risks of Large Deceleration

Real-world hazards of emergency stops

✅ Any Two Valid Risks (1 mark each)

  • The brakes will overheat (which can cause brake fade or failure). [1]
  • The driver may lose control of the vehicle / car skids. [1]

🧠 Exam Tip

Keep your points specific to the physics of the vehicle. Avoid vague statements like "there might be an accident" or "the driver gets hurt" unless you explicitly link them to injury caused by large seatbelt forces or skidding into another vehicle.

Topics

Physics · P1: Energy · P5: Forces

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