OxfordAQA International GCSE Physics
OxfordAQA International GCSE Physics 3.2 Energy Exam Questions
Free OxfordAQA International GCSE Physics revision for 3.2 Energy: what you need to know, common mistakes and exam-style questions with answers. Covers work done, kinetic, gravitational and elastic potential energy, power, conservation and dissipation of energy, efficiency, Sankey diagrams and energy resources.
Practise 3.2 Energy with past papers
Once you have learnt this topic, find the 3.2 Energy questions in real OxfordAQA International GCSE Physics past papers and mark them with the mark scheme. Doing lots of real questions is the quickest way to learn how examiners ask about each idea.
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About OxfordAQA International GCSE Physics 3.2 Energy
Energy in OxfordAQA International GCSE Physics links forces to energy transfers. You calculate work done, kinetic energy, gravitational potential energy and elastic potential energy, and power as the rate of transfer. You then apply conservation of energy, describe how energy is dissipated by friction and air resistance, calculate efficiency and draw and interpret Sankey diagrams. The final part covers fuels and energy resources, including renewable technologies such as wave, solar and geothermal power. This topic builds on 3.1 Forces and is used again with electrical energy in 3.6. Examiners like multi-step questions where gravitational potential energy is converted into kinetic energy.
What you need to know
- Work done W = F x d, where d is the distance moved in the direction of the force. Work done against friction transfers energy by heating, as in vehicle brakes, meteors and spacecraft re-entry.
- Energy stores Kinetic energy Ek = 1/2 x m x v^2; doubling speed quadruples kinetic energy, which matters for road safety. Gravitational potential energy Ep = m x g x h. Elastic potential energy Ee = 1/2 x k x e^2 within the limit of proportionality.
- Power Power is the rate of energy transfer or work done: P = E / t and P = W / t, measured in watts (1 W = 1 J/s).
- Conservation and dissipation Energy can be transferred usefully, stored or dissipated but cannot be created or destroyed. Energy that is not useful is usually dissipated to the surroundings by heating. A pendulum transfers energy between kinetic and gravitational potential stores (separate Physics).
- Efficiency Efficiency = useful energy out / total energy in, or useful power out / total power in, as a decimal or multiplied by 100 for a percentage. It can never be more than 1 (100%).
- Sankey diagrams The width of each arrow is proportional to the amount of energy. The total width in equals the total width out because energy is conserved.
- Energy resources Fuels are chosen for ease of storage, energy content and safety. Compare resources by whether they are renewable, reliability and environmental impact of extraction, use and disposal. Learn advantages and disadvantages of wave, solar and geothermal power and other renewables.
Common mistakes in 3.2 Energy
- Forgetting to square the speed in Ek = 1/2 m v^2. Square v first, then multiply by m and halve.
- Saying energy is lost or used up. Say energy is dissipated or transferred to the surroundings, usually by heating.
- Giving an efficiency greater than 100% or 1. If this happens, the useful and total values have been swapped.
- Using height in centimetres or mass in grams. Convert to metres and kilograms before calculating.
- Saying renewable resources never cause pollution. They are not used up, but building and installing them still has environmental impacts.
Try three 3.2 Energy exam-style questions
1. A 50 kg diver falls 4.0 m. Calculate the gravitational potential energy transferred and her speed as she enters the water, ignoring air resistance. Take g = 9.8 N/kg. (4 marks)
Show the mark scheme answer
Ep = 50 x 9.8 x 4.0 = 1960 J; Ek = 1960 J; 1960 = 1/2 x 50 x v^2 so v^2 = 78.4; v = 8.9 m/s.
2. A motor is supplied with 800 J and does 200 J of useful work. Calculate its efficiency. (2 marks)
Show the mark scheme answer
200 / 800 = 0.25; = 25%.
3. A kettle transfers 180 000 J in 90 s. Calculate its power. (2 marks)
Show the mark scheme answer
P = E / t = 180 000 / 90; = 2000 W (2 kW).
3.2 Energy FAQs
What does OxfordAQA International GCSE Physics 3.2 Energy cover?
It covers work done, kinetic, gravitational and elastic potential energy, power, conservation and dissipation of energy, efficiency, Sankey diagrams and the use of fuels and energy resources.
Which paper is 3.2 Energy examined in?
OxfordAQA International GCSE Physics has two equally weighted papers, Paper 1 and Paper 2, each 1 hour 30 minutes and 90 marks. Content from any part of the specification can appear in either paper.
How do I tackle energy conversion questions?
Identify the store at the start and the end, write that the energy transferred out of one equals the energy into the other (if none is dissipated), then set the two equations equal and rearrange, for example m g h = 1/2 m v^2.
