AQA GCSE Combined Science: Trilogy Physics Paper 2 (Foundation), November 2021: Question 5

✅ Correct Answer

Increases (or goes up / gets bigger).

💡 Key Knowledge

Air resistance is a frictional drag force that increases as the speed of an object moving through a fluid increases.

✅ Correct Answer

less than

"As the rocket aeroplane starts to accelerate along the runway, the lift force on the wings will be less than the weight of the rocket aeroplane."

🧠 Exam Technique

• If lift were greater than weight, the plane would accelerate upwards into the air.
• If lift were equal to weight, the plane would be just on the verge of lifting off.
• As it starts to accelerate along the runway, it is firmly on the ground, so lift is still less than weight.

📐 Step-by-Step Calculation

Step 1: Identify values & equation

average speed (v) = 35 m/s
time (t) = 14 s
distance = average speed × time

Step 2: Substitute values

distance = 35 × 14

Step 3: Calculate final answer

Distance = 490 m

❌ Common Errors

• Dividing speed by time ( 35 ÷ 14 = 2.5 ) instead of multiplying. The formula was given directly in the question—always read carefully!
• Arithmetic slips when multiplying without a calculator.

✅ Correct Equation

work done = force × distance

or in symbols: W = Fs (or W = Fd )

🧠 Exam Technique

Any correct rearrangement is also accepted, e.g.:

force = work done ÷ distance ( F = W / s )

Warning: Do not write just letters without standard meaning. Stick to words or the standard spec symbols ( W, F, s ).

📐 Step-by-Step Calculation

Step 1: Write down values
s = 270 m
W = 54 000 000 J

Step 2: Substitute into formula
54 000 000 = F × 270

Step 3: Rearrange to solve for force (F)
F = 54 000 000 ÷ 270

Step 4: State final value with units
Average force = 200 000 N (or 2 × 10⁵ N / 200 kN )

❌ Common Calculation Traps

• Counting zeros incorrectly: 54 000 000 has six zeros. Double check when entering into your calculator.
• Multiplying instead of dividing: Calculating 54 000 000 × 270 gives a nonsensical massive number.

💡 The Key Scientific Paradox

At first glance, the rocket aeroplane seems more dangerous because its hourly radiation dose is double (0.006 vs 0.003 mSv/hr).

HOWEVER: The rocket travels 32 times faster, so it completes the journey in 1/32 of the time!

Therefore, the overall radiation dose received during the entire flight is significantly lower on the rocket aeroplane.

📐 Crucial Calculations (Required for Level 2 / 4–6 Marks)

1. Speed ratio:
8000 ÷ 250 = 32
The rocket is 32× faster (or jet takes 32× longer).

2. Dose rate ratio:
0.006 ÷ 0.003 = 2
Rocket has 2× higher hourly dose rate.

3. Overall total dose ratio:
Total dose = dose rate × time
Relative jet dose = 1 × 32 = 32
Relative rocket dose = 2 × 1 = 2
Jet passenger receives 32 ÷ 2 = 16 times greater total radiation dose!

✅ Model 6-Mark Structure

• Journey comparison: Since the journey distance is the same, journey time depends entirely on speed.
• Speed comparison: The rocket aeroplane travels at 8000 m/s compared to 250 m/s for the jet, making it 32 times faster. This means the jet spends 32 times longer in the air.
• Dose rate comparison: The rocket exposes passengers to 0.006 mSv/hour, which is twice (2×) the rate of the jet (0.003 mSv/hour).
• Total radiation dose: Overall dose is dose rate multiplied by time. Because the jet takes 32× longer but only has half the dose rate, the total dose received in the jet aeroplane is 16 times greater than in the rocket plane.
• Biological risks & consequences: Ionising radiation can cause gene mutations, DNA damage, and increase the risk of cancers (e.g. skin cancer).
• Conclusion: The risk of radiation damage is therefore significantly higher for a passenger in the jet aeroplane because of the much longer exposure time.

🧠 Level Descriptors & Examiner Notes

Level 2 (4–6 marks): Scientifically relevant features identified, differences made clear, magnitude of differences noted (e.g. 32× faster, 2× dose rate), links made to total exposure, and must include a calculation.

Level 1 (1–3 marks): Basic comparisons (e.g. rocket is faster, rocket has higher dose rate) but no quantification or fails to realise that shorter flight time reduces total dose.