AQA GCSE Combined Science: Trilogy Physics Paper 1 (Higher), 2021: Question 3

✅ Correct answer

Solar

Also accepted: biofuel, biodiesel, wave power.

💡 Key knowledge

• Renewable means the energy source is replaced naturally.
• On a boat, solar panels are a common valid example because they can generate electricity without fuel.

🧠 Exam technique

• Give a single clear example.
• Use the exact name of the energy resource.
• For 1 mark, no explanation is needed.

❌ Common errors

• Writing just renewable is too vague.
• Giving a non-renewable source like coal, oil or gas loses the mark.
• Writing sun instead of solar may be accepted in context, but solar is safer.

✅ Correct answers

Any two of the following:

• Sometimes there is no wind, so the battery can still be charged using the generator.
• When there is wind less fuel is burned, so the generator is used less often.
• If one system fails, the other can still generate electricity.

💡 Key knowledge

• Wind turbines depend on wind, so they are not reliable all the time.
• A generator gives backup power, but it burns fossil fuel.
• The mark scheme accepts the idea that the turbine and generator act as a backup system for each other.

🧠 Exam technique

• Give two separate reasons for 2 marks.
• Make each reason different.
• Use cause-and-effect language: because, so, therefore.

❌ Common errors

• Repeating the same idea twice in different words only gets 1 mark.
• Saying only it is useful is too vague.
• Do not just state it has two power sources without saying why that helps.

✅ Correct answers

One valid explanation could be:

• Carbon dioxide is released, which increases global warming / the greenhouse effect.
• Sulfur dioxide or NOx emissions can cause acid rain.
• Particulates or NOx emissions can harm living organisms.

💡 Key knowledge

• Burning fossil fuels releases gases into the atmosphere.
• Carbon dioxide is a greenhouse gas.
• Sulfur dioxide and nitrogen oxides can contribute to acid rain.
• Particulates can damage health, especially the lungs.

🧠 Exam technique

• For 2 marks, give impact + explanation.
• Example: Burning fossil fuels releases carbon dioxide, which increases the greenhouse effect and causes global warming.
• Use the word because to link the pollutant to the environmental effect.

❌ Common errors

• Only naming a pollutant gets just 1 mark.
• Saying it pollutes the air is too vague for full marks.
• Mixing up global warming and acid rain loses clarity if the explanation is wrong.

📐 Calculations: step-by-step

1. Convert kilojoules to joules: 81 kJ = 81 000 J
2. Use the equation: KE = 0.5 × m × v²
3. Substitute values: 81 000 = 0.5 × 8000 × v²
4. Rearrange: v = √(81 000 ÷ (0.5 × 8000))
5. Calculate: v = 4.5 m/s

✅ Correct answer

Speed = 4.5 m/s

Marks were awarded for:
1 mark for converting kJ to J
1 mark for correct substitution
1 mark for rearranging correctly
1 mark for the final answer

🧠 Exam technique

• Always write the equation first.
• Convert kJ to J before calculating.
• Show the rearrangement clearly to gain method marks.
• Give the answer with the unit m/s.

❌ Common errors

• Forgetting to convert 81 kJ into joules.
• Using KE = m × v² and missing the 0.5 .
• Using the wrong rearrangement, such as multiplying instead of dividing.
• Leaving the answer without units.

📐 Calculations: step-by-step

1. Use the equation: GPE = m × g × h
2. Substitute values: 19 600 = 8000 × 9.8 × Δh
3. Rearrange: Δh = 19 600 ÷ (8000 × 9.8)
4. Calculate: Δh = 0.25 m

✅ Correct answer

Change in height = 0.25 m

Top answers showed the correct equation, correct substitution, and a clear final value.

🧠 Exam technique

• Use the exact symbols: m , g , h .
• If the question says change in height, write Δh or height change .
• Check units: energy in J, mass in kg, g in N/kg, height in m.

❌ Common errors

• Using the wrong equation, such as kinetic energy instead of gravitational potential energy.
• Dividing by only one of the factors instead of 8000 × 9.8.
• Forgetting the unit m.
• Mixing up increase in GPE with increase in mass.

💡 Strong responses

• Used precise science words: solar, carbon dioxide, global warming, acid rain.
• Showed full calculation steps rather than jumping straight to the answer.
• Linked cause and effect clearly in the environmental question.

❌ Where students lost marks

• Too much vague description with not enough science detail.
• Missing the unit in calculations.
• Not converting kJ to J.
• Giving only one valid reason where two were asked.

🧠 Fast revision checklist

• Renewable example = solar.
• Backup power helps when wind is absent.
• Fossil fuels release CO₂, SO₂, NOx, and particulates.
• Use KE = 0.5 × m × v² .
• Use GPE = m × g × h .