IGCSE Physics 1.7 Energy, Work and Power MCQs – 30 Practice Questions with Answers (Cambridge 0625)
Thirty original practice questions for Cambridge IGCSE Physics (0625), Section 1.7 Energy, Work and Power, covering energy stores and transfers, work done and power, and efficiency and energy resources. Every question has a worked answer hidden underneath it, and g = 10 N/kg is used in all calculations.
Formula recap for Section 1.7
Work done: W = F × d · Power: P = W / t = E / t · Kinetic energy: KE = 0.5 × m × v2 · Change in gravitational potential energy: ΔGPE = m × g × Δh · Efficiency = (useful energy output / total energy input) × 100%
Need the full list? Open the IGCSE Physics Formula Sheet (Cambridge 0625).
Energy Stores & Transfers
Q1. Which energy store increases when an elastic band is stretched?
- (A) Kinetic store
- (B) Elastic potential store
- (C) Chemical store
- (D) Nuclear store
Show Answer
Answer: B – Stretching an elastic band stores energy in its elastic potential store. This energy is transferred back to the kinetic store when the band is released and contracts.
Q2. A train travels along a straight, level track. Which store holds energy because the train is moving?
- (A) Gravitational potential store
- (B) Elastic potential store
- (C) Kinetic store
- (D) Electrostatic store
Show Answer
Answer: C – Any moving object has energy in its kinetic store. The faster it moves, or the greater its mass, the more energy is in this store.
Q3. An electric lamp is connected to a battery and switched on. How is energy transferred from the battery to the lamp?
- (A) By heating
- (B) By mechanical working
- (C) By radiation only
- (D) Electrically, by the electric current
Show Answer
Answer: D – In an electric circuit, energy is transferred electrically by the current, from the chemical store of the battery to the lamp, where it is then transferred to the surroundings by light and heating.
Q4. A ball is dropped and falls freely. Air resistance is negligible. Which statement about the energy transfers is correct?
- (A) The total energy of the ball increases as it falls.
- (B) The energy lost from the gravitational potential store equals the energy gained by the kinetic store.
- (C) The kinetic store decreases as the ball speeds up.
- (D) Energy is destroyed at the moment the ball hits the ground.
Show Answer
Answer: B – By the principle of conservation of energy, energy is never created or destroyed. With no air resistance, all the energy lost from the gravitational potential store appears as kinetic energy, so the total stays the same.
Q5. A motor is shown on a Sankey diagram. It takes in 200 J of electrical energy and transfers 50 J to the kinetic store of its load. How much energy is wasted, and how does the diagram show it?
- (A) 150 J, shown by the wasted-energy arrow that branches off
- (B) 50 J, shown by the main output arrow
- (C) 200 J, shown by the input arrow
- (D) 250 J, shown by adding the widths of all the arrows
Show Answer
Answer: A – Wasted energy = total input − useful output = 200 − 50 = 150 J. On a Sankey diagram the width of each arrow is proportional to the energy it represents, and the wasted energy is shown by the arrow that branches off, usually downwards.
Q6. [Supplement] A ball of mass 2.0 kg moves at a speed of 3.0 m/s. What is its kinetic energy?
- (A) 3.0 J
- (B) 6.0 J
- (C) 9.0 J
- (D) 18 J
Show Answer
Answer: C – KE = 0.5 × m × v2 = 0.5 × 2.0 × 3.02 = 0.5 × 2.0 × 9.0 = 9.0 J. (18 J is the trap answer from forgetting the 0.5, and 6.0 J is just m × v.)
Q7. [Supplement] A stone of mass 0.50 kg is thrown at a speed of 10 m/s. What is its kinetic energy?
- (A) 5.0 J
- (B) 25 J
- (C) 50 J
- (D) 100 J
Show Answer
Answer: B – KE = 0.5 × m × v2 = 0.5 × 0.50 × 102 = 0.25 × 100 = 25 J. (50 J is m × v2 without the 0.5.)
Q8. [Supplement] A box of mass 5.0 kg is lifted onto a shelf 2.0 m above the floor. By how much does its gravitational potential energy increase?
- (A) 10 J
- (B) 25 J
- (C) 70 J
- (D) 100 J
Show Answer
Answer: D – ΔGPE = m × g × Δh = 5.0 × 10 × 2.0 = 100 J. The gain in gravitational potential energy depends on the vertical height gained, which is 2.0 m here.
Q9. [Supplement] An object gains 240 J of gravitational potential energy when it is raised through a height of 4.0 m. What is the mass of the object?
- (A) 6.0 kg
- (B) 24 kg
- (C) 60 kg
- (D) 960 kg
Show Answer
Answer: A – ΔGPE = m × g × Δh, so m = 240 / (10 × 4.0) = 240 / 40 = 6.0 kg.
Q10. Which of these is an example of energy being transferred by radiation?
- (A) Sunlight warming the surface of the Earth
- (B) A falling weight turning the blades of a fan
- (C) An electric current heating the element of a kettle
- (D) A stretched spring launching a toy car
Show Answer
Answer: A – Light and infrared radiation from the Sun travel through empty space as waves, so this is a transfer by radiation. The falling weight is mechanical working, the kettle element is an electrical transfer, and the spring is a transfer from the elastic potential store.
Work Done & Power
Q11. A force of 20 N pushes a trolley a distance of 3.0 m in the direction of the force. How much work is done by the force?
- (A) 6.7 J
- (B) 23 J
- (C) 60 J
- (D) 600 J
Show Answer
Answer: C – Work done W = F × d = 20 × 3.0 = 60 J. One joule of work is done when a force of one newton moves through one metre in the direction of the force.
Q12. A student lifts a bag of mass 4.0 kg from the floor onto a table 1.5 m high. How much work does the student do against gravity?
- (A) 6.0 J
- (B) 60 J
- (C) 90 J
- (D) 600 J
Show Answer
Answer: B – The weight of the bag is m × g = 4.0 × 10 = 40 N. Work done against gravity = force × vertical distance = 40 × 1.5 = 60 J. This equals the gain in gravitational potential energy.
Q13. A man pushes a heavy crate with a force of 300 N, but the crate does not move at all. How much work does he do on the crate?
- (A) 0 J
- (B) 100 J
- (C) 300 J
- (D) 900 J
Show Answer
Answer: A – Work done = force × distance moved in the direction of the force. The distance moved is zero, so W = 300 × 0 = 0 J, however large the force is.
Q14. A motor does 600 J of work in 20 s. What is the power of the motor?
- (A) 12 000 W
- (B) 300 W
- (C) 12 W
- (D) 30 W
Show Answer
Answer: D – Power P = W / t = 600 / 20 = 30 W. (12 000 W comes from multiplying instead of dividing.)
Q15. A crane lifts a load and transfers 12 000 J of energy in 1.0 minute. What is the power of the crane?
- (A) 20 W
- (B) 200 W
- (C) 12 000 W
- (D) 720 000 W
Show Answer
Answer: B – First convert the time: 1.0 minute = 60 s. Then P = E / t = 12 000 / 60 = 200 W. (Using 1 instead of 60 gives the trap answer 12 000 W.)
Q16. One watt is equal to
- (A) one joule per second
- (B) one joule per metre
- (C) one newton per second
- (D) one joule multiplied by one second
Show Answer
Answer: A – Power is the rate of doing work or transferring energy, so 1 W = 1 J/s. A 100 W device transfers 100 joules of energy every second.
Q17. Pump A transfers 900 J of energy in 30 s. Pump B transfers 1200 J of energy in 60 s. Which statement is correct?
- (A) Pump B is more powerful because it transfers more energy in total.
- (B) Both pumps have exactly the same power.
- (C) Pump A is more powerful: A is 30 W and B is 20 W.
- (D) Pump B is more powerful: B is 40 W and A is 15 W.
Show Answer
Answer: C – Power of A = 900 / 30 = 30 W. Power of B = 1200 / 60 = 20 W. Power depends on the rate of transfer, not the total energy, so A is more powerful even though it transfers less energy overall.
Q18. An electric heater transfers 90 000 J of energy in 1.0 minute. What is the power of the heater?
- (A) 150 W
- (B) 1500 W
- (C) 9000 W
- (D) 90 000 W
Show Answer
Answer: B – P = E / t = 90 000 / 60 = 1500 W, i.e. 1.5 kW, a typical value for an electric heater.
Q19. [Supplement] A car travels at a steady speed of 25 m/s. Its engine provides a constant driving force of 800 N. What power does the engine develop?
- (A) 32 W
- (B) 825 W
- (C) 20 000 W
- (D) 20 W
Show Answer
Answer: C – For a force moving at speed v, P = F × v = 800 × 25 = 20 000 W = 20 kW. (32 W comes from dividing F by v instead of multiplying.) Because the speed is steady, this power exactly balances the power used against resistive forces.
Q20. A box is dragged across a rough floor. The friction force opposing the motion is 15 N and the box moves 8.0 m. How much work is done against friction?
- (A) 1.9 J
- (B) 23 J
- (C) 150 J
- (D) 120 J
Show Answer
Answer: D – Work done against friction = friction force × distance = 15 × 8.0 = 120 J. This energy is transferred to the internal (thermal) stores of the box and the floor, which is why surfaces warm up when they are rubbed together.
Efficiency & Energy Resources
Q21. A television receives 500 J of electrical energy. It produces 350 J of useful light and sound energy. What is the efficiency of the television?
- (A) 35%
- (B) 65%
- (C) 70%
- (D) 143%
Show Answer
Answer: C – Efficiency = (useful energy output / total energy input) × 100% = (350 / 500) × 100% = 70%. The remaining 150 J is wasted, mainly as thermal energy.
Q22. A motor has an input power of 200 W and a useful output power of 150 W. What is its efficiency?
- (A) 75%
- (B) 67%
- (C) 50%
- (D) 133%
Show Answer
Answer: A – Efficiency can be calculated from powers just as from energies: (150 / 200) × 100% = 75%. The other 50 W of input power is wasted, heating the motor and its surroundings.
Q23. Why is the efficiency of a real machine always less than 100%?
- (A) Some of the input energy is always transferred to wasted stores, for example by friction and heating to the surroundings.
- (B) Some of the input energy is destroyed by the machine.
- (C) The machine creates extra energy that is not counted in the input.
- (D) The useful output of a machine is always greater than its input.
Show Answer
Answer: A – Energy is always conserved, so it cannot be destroyed or created. But in every real machine some input energy is dissipated to wasted stores, such as the internal (thermal) store of the surroundings, so the useful output is always less than the input.
Q24. A machine is supplied with 800 J of energy, of which 200 J is wasted. What is the efficiency of the machine?
- (A) 20%
- (B) 25%
- (C) 60%
- (D) 75%
Show Answer
Answer: D – Useful output = 800 − 200 = 600 J. Efficiency = (600 / 800) × 100% = 75%. (25% is the trap answer from using the wasted energy as the useful output.)
Q25. Which of the following is a non-renewable energy resource?
- (A) Wind
- (B) Hydroelectric power
- (C) Natural gas
- (D) Solar power
Show Answer
Answer: C – Natural gas is a fossil fuel. Fossil fuels took millions of years to form and are being used up far faster than they can be replaced, so they are non-renewable. Wind, water and sunlight are continually available and are renewable.
Q26. What is the main disadvantage of generating electricity using solar cells?
- (A) They release carbon dioxide while generating electricity.
- (B) They cause the Sun to run out faster.
- (C) They cannot produce any electricity during the day.
- (D) Their output varies with the weather and drops to zero at night.
Show Answer
Answer: D – Solar cells produce no carbon dioxide while generating, and they work best in daylight, but their output is unreliable: it falls on cloudy days and is zero at night, so other sources or storage are needed to meet demand.
Q27. Hydroelectric power stations have an advantage over wind farms because they
- (A) can be started up quickly and controlled to meet sudden changes in demand
- (B) do not need a supply of water
- (C) produce the most electricity at night
- (D) never damage habitats or landscapes
Show Answer
Answer: A – Water stored behind a dam can be released when demand rises, so hydroelectric output is reliable and controllable, unlike wind which depends on the weather. Note (D) is false: building a dam floods a large area of land and can damage habitats.
Q28. Burning fossil fuels is a major concern mainly because it
- (A) only causes acid rain and nothing else
- (B) releases carbon dioxide, a greenhouse gas that contributes to climate change
- (C) produces radioactive waste that must be stored for thousands of years
- (D) uses up all the water in rivers and lakes
Show Answer
Answer: B – Coal, oil and natural gas all release carbon dioxide when burned. Carbon dioxide is a greenhouse gas, and increasing its concentration in the atmosphere is the main cause of the current climate change. Radioactive waste is an issue for nuclear power, not fossil fuels.
Q29. Geothermal energy can only be used in a limited number of places in the world. Why?
- (A) It only works during the summer months.
- (B) It produces too much noise for people living nearby.
- (C) It needs hot rocks close to the surface of the Earth, which are found mainly in volcanic regions.
- (D) It needs a large river flowing past the power station.
Show Answer
Answer: C – Geothermal power uses heat from underground rocks to produce steam. It is only practical where those hot rocks are near the surface, for example in volcanic areas such as Iceland. Where it can be used, it is reliable and produces very little carbon dioxide.
Q30. A fuel with a high energy density is useful in a vehicle. Energy density means
- (A) the total mass of fuel the vehicle is able to carry
- (B) how quickly the fuel is able to burn
- (C) whether the fuel is renewable or non-renewable
- (D) the energy released per unit mass (per kilogram) of the fuel
Show Answer
Answer: D – Energy density is the energy stored per kilogram of fuel. A vehicle fuel with a high energy density releases a lot of energy from a small mass, so the vehicle does not have to carry a heavy load of fuel. Petrol has a high energy density, which is one reason it is hard to replace in vehicles.
Keep revising Section 1.7
Revise every equation on the IGCSE Physics Formula Sheet (Cambridge 0625), then explore the rest of our free physics practice on the Physics MCQs hub, with topic pages for GCSE, IGCSE, A-Level and AP.
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