Edexcel GCSE Physics
Edexcel GCSE Physics Topic 8: Energy, Forces Doing Work Exam Questions
Free Edexcel GCSE Physics exam questions for Topic 8: Energy, Forces Doing Work, with a mark scheme for every pack. Covers energy transfers in systems, work done by forces, power, energy dissipation and efficiency of mechanical and electrical transfers.
Topic 8: Energy, Forces Doing Work exam questions
2 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About Edexcel GCSE Physics Topic 8: Energy, Forces Doing Work
Topic 8 opens Paper 2 and revisits energy from the point of view of forces. When a force moves an object, it does work, transferring energy between stores. You need to describe energy transfers in closed systems mechanically, electrically, by heating and by radiation, calculate work done using E = F x d, and calculate power as the rate of energy transfer. The topic builds directly on Topic 3 Conservation of Energy and links to Topic 9 on forces and Topic 10 on electrical power. Examiners like combined calculations, such as working out work done and then power, and explanations of where energy is dissipated.
What you need to know
- Energy transfers Describe changes in energy stores when a system changes, for example chemical to kinetic to thermal when a car brakes. Energy is transferred mechanically, electrically, by heating or by radiation.
- Work done Work done = force x distance moved in the direction of the force (E = F x d). Work done is measured in joules and equals the energy transferred. 1 J is the work done when a force of 1 N moves 1 m.
- Work against friction When work is done against friction, energy is dissipated as thermal energy, raising the temperature of the surfaces and surroundings.
- Power Power = work done / time taken (P = E / t). Power is measured in watts, where 1 W = 1 J/s. A more powerful device transfers the same energy in less time.
- Efficiency Efficiency = useful energy transferred / total energy supplied. Reduce wasted energy by lubrication, streamlining and insulation.
- Closed systems In a closed system no energy enters or leaves, so the total energy is constant even though it is redistributed between stores.
Common mistakes in Topic 8: Energy, Forces Doing Work
- Using the total distance when the force is not along the direction of motion. Only the distance moved in the direction of the force counts.
- Confusing power with energy. Power is energy transferred per second, measured in watts, not joules.
- Forgetting to convert minutes to seconds before using P = E / t.
- Saying work is done when holding a heavy object still. If there is no movement in the direction of the force, no work is done on the object.
- Writing that friction destroys energy. Friction transfers energy to the thermal store of the surroundings.
Try three Topic 8: Energy, Forces Doing Work exam-style questions
1. A student pushes a box with a force of 250 N for 12 m in 20 s. Calculate the work done and the power. (4 marks)
Show the mark scheme answer
E = F x d = 250 x 12; = 3000 J; P = E / t = 3000 / 20; = 150 W.
2. A lift motor does 48 000 J of work in 1.0 minute. Calculate its power. (2 marks)
Show the mark scheme answer
P = E / t = 48 000 / 60; = 800 W.
3. Describe the energy transfers when a cyclist brakes to a stop. (3 marks)
Show the mark scheme answer
Energy is transferred from the kinetic store of the cyclist and bike; by work done by friction between brake pads and wheel; to the thermal store of the brakes and surroundings.
Topic 8: Energy, Forces Doing Work FAQs
What does Edexcel GCSE Physics Topic 8 Energy, Forces Doing Work cover?
It covers energy transfers in systems, work done by forces, power and the efficiency of energy transfers.
Which paper is Topic 8 examined on?
Topic 8 is assessed on Paper 2, which covers Topics 1 and 8 to 15.
What equations do I need for Energy, Forces Doing Work?
Learn work done = force x distance moved in the direction of the force, power = work done / time and efficiency = useful energy / total energy supplied.
