Lesson 3.3.3

3.3.3 Power Quiz: OCR Physics, Unit 2

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.3.3, Power: 20 multiple choice questions for the OCR Physics (H156), Unit 2: Forces and motion, written with Revision Ninja.

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The 20 questions

  1. How is power defined in terms of work done and time taken?

    • Force x time
    • Work / time
    • Work x time
    • Energy x time

  2. The unit of power, the watt, is equal to:

    • J s^-1
    • kg m s^-2
    • J s
    • N s

  3. For a force F moving an object at speed v in the direction of the force, the power is:

    • P = F + v
    • P = F v^2
    • P = F / v
    • P = F v

  4. One kilowatt-hour is a unit of:

    • Energy
    • Time
    • Force
    • Power

  5. Which formula expresses power in terms of constant force and velocity?

    • P = F v^2
    • P = F t
    • P = F v
    • P = F / v

  6. How is the efficiency of a mechanical system calculated?

    • Total / useful energy
    • Useful / total energy
    • Useful + total energy
    • Useful x total energy

  7. A motor lifts a load at constant speed v against gravity. The power output is:

    • m g v
    • m v^2
    • m g t
    • m g / v

  8. A heater transfers 500 J of energy in 10 s. What is its power?

    • 500 W
    • 5000 W
    • 0.02 W
    • 50 W

  9. A car travelling at 20 m s^-1 has a driving force of 1500 N. What is the power developed?

    • 300 kW
    • 75 kW
    • 30 kW
    • 3 kW

  10. A 2.0 kW kettle runs for 15 minutes. How much energy does it transfer?

    • 0.25 kWh
    • 0.5 kWh
    • 2.0 kWh
    • 30 kWh

  11. A motor takes in 500 W and produces 120 W of useful output power. What is its efficiency?

    • 42%
    • 24%
    • 60%
    • 76%

  12. A 50 kg load is raised at a steady 0.4 m s^-1. What is the power needed? Use g = 9.8 m s^-2.

    • 1960 W
    • 196 W
    • 19.6 W
    • 490 W

  13. A 1.5 kW heater runs for 4 hours. At 12p per kWh, what does it cost?

    • 72p
    • 6p
    • 18p
    • 48p

  14. A car at a steady 10 m s^-1 works against a resistive force of 3000 N. What power must its engine supply?

    • 30 kW
    • 300 kW
    • 300 W
    • 3 kW

  15. A 2 kg mass is raised through 10 m in 4 s at constant speed. What is the power output? Use g = 9.8 m s^-2.

    • 4.9 W
    • 19.6 W
    • 49 W
    • 98 W

  16. A motor has 80% efficiency and delivers 600 W of useful output. What is the input power?

    • 1200 W
    • 480 W
    • 750 W
    • 600 W

  17. A 1200 kg car climbs a height of 10 m in 20 s at constant speed. Using g = 9.8 m s^-2, what average power does it need?

    • 2.9 kW
    • 0.59 kW
    • 5.9 kW
    • 11.8 kW

  18. A constant force of 800 N acts on a vehicle whose speed rises to 20 m s^-1. What is the instantaneous power at that speed?

    • 8 kW
    • 16 kW
    • 12 kW
    • 4 kW

  19. A winch raises a 400 kg load at a steady 0.5 m s^-1 with an efficiency of 75%. Using g = 9.8 m s^-2, what input power is needed?

    • 2.0 kW
    • 1.5 kW
    • 3.9 kW
    • 2.6 kW

  20. A 10 kg mass accelerates uniformly from rest at 2 m s^-2 for 5 s. What is its average power over this time?

    • 50 W
    • 500 W
    • 100 W
    • 200 W

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