AQA GCSE Combined Science: Trilogy Physics Paper 2 (Higher), 2022: Question 7

✅ Correct answer

• Draw two vertical arrows in opposite directions away from point X.
• One arrow points downwards from X for the weight.
• One arrow points upwards for the tension/support force.
• The two arrows must be the same length because the apple is stationary, so the forces are balanced.

💡 Key knowledge

• A stationary object has balanced forces.
• Balanced forces mean resultant force = 0 N.
• If resultant force is zero, the object does not accelerate.
• The mark scheme allows the upward arrow to start from the stem.
• Labels are not essential here because the mark scheme says to ignore labels.

🧠 Exam technique

• Because the question says the apple is stationary, immediately think: forces are equal and opposite.
• In a force diagram, arrow direction and length matter.
• For full marks, don’t just draw two arrows — make sure they are the same size.

❌ Common errors

• Drawing arrows of different lengths even though the apple is stationary.
• Drawing arrows that are not vertical.
• Forgetting that the downward force should act from the centre of mass (X).
• Adding extra forces that do not act directly on the apple.

✅ Correct answer

Distance = 1.2 m

📐 Calculations

1. Use acceleration equation:
   a = Δv / t
2. Substitute values:
   9.8 = Δv / 0.5
3. Find the change in velocity:
   Δv = 9.8 × 0.5 = 4.9 m/s
4. Since the initial velocity is 0 m/s, the final velocity is:
   v = 4.9 m/s
5. Now use:
   v² − u² = 2as
6. Substitute values:
   4.9² − 0² = 2 × 9.8 × s
7. Rearrange:
   s = 4.9² / (2 × 9.8)
8. Calculate:
   s = 24.01 / 19.6 = 1.225...
9. Give the final answer as:
   s = 1.2 m

💡 Key knowledge

• u = initial velocity
• v = final velocity
• a = acceleration
• t = time
• s = distance moved
• This question expects you to use equations from the Physics Equations Sheet in a logical sequence.
• The method in the mark scheme finds final velocity first, then uses it to find distance.

🧠 Exam technique

• Show every stage clearly — this question is worth 6 marks, so method marks matter.
• Even if you make an earlier mistake, you can still get later marks by using your value correctly. This is called error carried forward.
• Write units clearly: m/s, m/s², and m.
• Use the exact calculator value until the end, then round your final answer.

❌ Common errors

• Using the wrong equation straight away without finding v.
• Forgetting that u = 0 m/s.
• Writing v = 9.8 / 0.5 instead of v = 9.8 × 0.5 .
• Not squaring v in v² − u² = 2as .
• Giving the answer as 1.22 m — the mark scheme specifically says this should not be accepted.

✅ Correct answers

Best full-mark evaluation:

• As the apple falls, air resistance increases.
• So the resultant force decreases.
• So the acceleration decreases.
• Therefore the acceleration is not constant, so this is not a good assumption.

Alternative full-mark evaluation also allowed:

• The apple only falls for a short time/distance.
• So air resistance is negligible.
• Therefore the resultant force is approximately constant.
• So the acceleration is approximately constant, making it a good assumption.

💡 Key knowledge

• Weight acts downward and is roughly constant.
• Air resistance acts upward and increases as speed increases.
• Resultant force = weight − air resistance.
• If resultant force changes, acceleration changes because of F = ma.
• This means falling objects do not always accelerate at exactly 9.8 m/s² once air resistance matters.

🧠 Exam technique

• This is an evaluate question, so do more than state one fact.
• Link ideas in a chain:
  air resistance increases → resultant force decreases → acceleration decreases
• End with a judgement such as:
  “so it is not a good assumption”
  or
  “so it is a reasonable assumption for a short fall”
• Top responses clearly explain why acceleration changes, not just that “air resistance exists”.

❌ Common errors

• Saying only “there is air resistance” without explaining the effect on resultant force or acceleration.
• Forgetting to make a final judgement about whether the assumption is good or not good.
• Confusing weight with resultant force.
• Saying the acceleration stays 9.8 m/s² no matter what, even when air resistance increases.

✅ 07.1

Two equal-length vertical arrows in opposite directions away from X.

✅ 07.2

v = 9.8 × 0.5 = 4.9 m/s

s = 4.9² / (2 × 9.8) = 1.2 m

✅ 07.3

As speed increases, air resistance increases, so resultant force and acceleration decrease. Therefore acceleration is not truly constant.