CIE A Level Physics
CIE A Level Physics Work, Energy and Power Exam Questions
Free CIE A Level Physics exam questions for Work, Energy and Power, with a mark scheme for every pack. Covers work done, conservation of energy, efficiency, gravitational potential energy, kinetic energy and power including P = Fv.
Work, Energy and Power exam questions
1 question pack 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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A-Level Physics Flashcards for 2027 Onwards
Every answer is written in mark scheme wording, so you learn exactly what examiners give marks for. Then test yourself with the questions on this page.
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About CIE A Level Physics Work, Energy and Power
Work, energy and power is Topic 5 of the Cambridge International AS & A Level Physics (9702) syllabus. It defines work as force times displacement in the direction of the force and uses the principle of conservation of energy to analyse mechanical systems. You must derive the expressions for gravitational potential energy and kinetic energy, calculate efficiency and use power equations including P = Fv. The topic connects Kinematics and Dynamics with later work on gases, electricity and fields. Examiners often combine energy transfers with motion on slopes or vehicles moving against resistive forces.
What you need to know
- Work done W = Fs cos θ, where s is the displacement and θ the angle between force and displacement. Work done by a gas expanding at constant pressure is W = pΔV.
- Energy conservation Energy cannot be created or destroyed, only transferred. Efficiency = useful energy output / total energy input (or useful power out / total power in).
- Potential and kinetic energy ΔEp = mgΔh for a uniform field near the Earth's surface; Ek = ½mv^2. Both formulae should be derived from W = Fs and the equations of motion.
- Power Power is the rate of doing work, P = W/t, in watts. For a force moving an object at constant velocity, P = Fv.
Common mistakes in Work, Energy and Power
- Using total distance rather than the displacement in the direction of the force when calculating work.
- Forgetting to include work done against friction or air resistance in energy conservation problems.
- Using P = Fv with the total driving force when the vehicle is accelerating and the question asks about resistive forces. Check which force the question needs.
- Giving efficiency greater than 1 or 100% because output and input were swapped.
- Applying mgΔh for large changes in height in a non-uniform field. It only applies near the Earth's surface.
Try three Work, Energy and Power exam-style questions
1. A motor of input power 250 W lifts a 20 kg mass vertically through 3.0 m in 4.0 s at constant speed. Calculate the efficiency of the motor. (3 marks)
Show the mark scheme answer
Useful energy = mgh = 20 × 9.81 × 3.0 = 589 J; useful power = 589/4.0 = 147 W; efficiency = 147/250 = 0.59 (59%).
2. Show that the kinetic energy of a mass m moving at speed v is ½mv^2. (3 marks)
Show the mark scheme answer
A constant force F accelerates the mass from rest through distance s, work done W = Fs; F = ma and v^2 = 2as so s = v^2/2a; W = ma × v^2/2a = ½mv^2.
3. A car moves at a constant 30 m s^-1 against a total resistive force of 600 N. Calculate the useful output power of the engine. (2 marks)
Show the mark scheme answer
Driving force = resistive force = 600 N at constant velocity; P = Fv = 600 × 30 = 1.8 × 10^4 W.
Work, Energy and Power FAQs
What does Cambridge AS & A Level Physics work, energy and power cover?
It covers work done, conservation of energy, efficiency, derivations of gravitational potential energy and kinetic energy, and power including P = Fv.
Which papers is work, energy and power examined in?
It is an AS Level topic assessed in Paper 1 and Paper 2, with energy ideas reused throughout the A Level topics.
Which derivations do I need to learn?
Learn how to derive ΔEp = mgΔh and Ek = ½mv^2 from W = Fs and the equations of motion, as these are named in the syllabus.
