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

✅ Correct answer

W = F × s

or written in words:

work done = force × distance

More precisely: distance is measured along the line of action of the force.

💡 Key knowledge

• Work done is the energy transferred by a force.
• Units: work done in joules (J), force in newtons (N), distance in metres (m).

🧠 Exam technique

This is a 1-mark recall question, so the exact equation must be correct. Do not invent a rearrangement unless asked.

❌ Common errors

• Writing F = W × s
• Mixing this up with power or speed equations
• Forgetting that distance must be in the direction of the force

✅ Correct answer

Average air resistance = 80 N

📐 Calculations

1. Use the equation W = F × s
2. Substitute the values:
   3 360 000 = F × 42 000
3. Rearrange:
   F = 3 360 000 ÷ 42 000
4. Calculate:
   F = 80 N

💡 Key knowledge

• Air resistance is a resistive force measured in newtons.
• Average force can be found from work done and distance travelled.
• The distance given is 42 000 m, so no unit conversion is needed.

🧠 Exam technique

For 3-mark calculations, examiners usually reward:

• correct substitution
• correct rearrangement
• correct final answer with unit

Even if you make an arithmetic slip, showing the method can still earn marks.

❌ Common errors

• Using the equation the wrong way round
• Multiplying instead of dividing by 42 000
• Leaving off the unit N
• Copying the work done value incorrectly

✅ Correct answer

Tick:

distance travelled = speed × time

💡 Key knowledge

This is the standard motion equation:

distance = speed × time

🧠 Exam technique

For multiple-choice or tick-box questions, read every option carefully. Wrong options are often common rearrangement mistakes.

❌ Common errors

• time = distance × speed is wrong
• speed = distance × time is wrong
• Forgetting that rearranging usually means dividing, not multiplying

✅ Correct answer

Average speed = 7.5 m/s

📐 Calculations

1. Start with:
   distance = speed × time
2. Substitute the values:
   42 000 = v × 5600
3. Rearrange:
   v = 42 000 ÷ 5600
4. Calculate:
   v = 7.5 m/s

💡 Key knowledge

• Average speed = total distance ÷ total time
• Distance must be in metres and time in seconds to give speed in m/s.
• Here the units already match, so no conversion is needed.

🧠 Exam technique

Use the symbol from the question if you want, but it is not essential. The key is clear method, correct calculator use, and the correct unit.

❌ Common errors

• Doing 5600 ÷ 42 000 instead of 42 000 ÷ 5600
• Writing the answer in the wrong unit
• Rounding badly or giving no final unit

✅ Correct answers

This is a level-of-response question. To reach the top level, you must give several valid reasons and clearly link each cause to what happens to speed.

A strong answer could be:

At the start of the race, the competitor accelerates, so their speed increases. The road is not flat, so speed increases downhill and decreases uphill. When going round a bend, the competitor may slow down. Towards the end of the race they may get tired, so the force they exert decreases and their speed decreases. If they sprint at some points, their speed increases. Changes in resistive forces such as air resistance can also make speed decrease or increase.

💡 Key knowledge

• Speed changes when forces change or conditions on the course change.
• Useful causes from the mark scheme include:
  • accelerating at the start
  • uphill or downhill sections
  • going round bends
  • tiring near the end
  • sprinting during the race
  • a puncture
  • changes in resistive forces
• The effect on speed must match the cause.

🧠 Exam technique

What gets into Level 2 (3–4 marks)?

• Give more than one reason.
• Explain the effect of each reason on speed.
• Link ideas logically, not as random bullet points.

Top answers were clear about cause → effect, for example:

the road is uphill → competitor slows down

competitor sprints → speed increases

❌ Common errors

• Listing causes but not saying what happens to speed
• Saying contradictory things, such as uphill makes speed increase
• Giving only one simple point, which limits the mark
• Being too vague, for example just saying “different forces act” with no explanation

Examiner insight: students often lost marks because they did not clearly link the reason to whether speed increases, decreases, or stops.

✅ Final answers

• 02.1 W = F × s
• 02.2 80 N
• 02.3 distance travelled = speed × time
• 02.4 7.5 m/s
• 02.5 Speed changes because of acceleration, hills, bends, tiredness, sprinting, punctures, and changing resistive forces.

💡 Final revision tip

In this question, most marks come from using the correct equation, rearranging carefully, and including units. For the longer explanation, link every cause directly to what happens to the competitor’s speed.