About Work, energy and power in A Level Physics
Work, energy and power is one of the 13 main topics in our A Level Physics (Cambridge (CAIE) 9702) question bank, and about 3% of its real questions come from it. Tayyari Karo has 21 real questions on this topic from 2021 to 2024, from Paper 1, Paper 2; 17 are multiple choice and marked instantly, and the rest are structured questions with a model answer. By difficulty: 13 medium, 7 easy, 1 hard.
Work through the questions below, then open the explanation for each one. Redo the ones you missed a few days later.
Try 6 real questions
These are real past-paper questions. Think of your answer first, then open the explanation.
May/June 2024 · Paper 1 · Work, energy and power
A box of weight 40 N is pushed with a horizontal force of 20 N along level ground for a distance of 2.4 m. The box is then lifted at constant velocity through a height of 1.6 m by a vertical force.
What is the total work done on the box by the two forces?
- 80 J
- 110 J
- 120 J
- 160 J
Show answer and explanation
Answer: B. 110 J
Work by horizontal force = 20 × 2.4 = 48 J. For the vertical lift at constant velocity, the applied force equals the weight, 40 N, so work = 40 × 1.6 = 64 J. Total = 48 + 64 = 112 J ≈ 110 J (2 s.f.).
October/November 2024 · Paper 1 · Work, energy and power
A ball of mass m is thrown up to height h in air with an initial velocity v, travelling from point P (ground) to point Q (ground) via the peak height h. Air resistance is negligible; g is the acceleration of free fall.
What is the total work done by the gravitational force on the ball during its flight from P to Q?
- zero
- ½mv²
- mgh
- 2mgh
Show answer and explanation
Answer: A. zero
The ball returns to the same height (P and Q are both on the ground), so the net displacement in the direction of gravity is zero and the total work done by gravity is zero.
October/November 2023 · Paper 1 · Work, energy and power
The input power to a television is Pin. The useful sound and light power emitted by the television is Pout.
What is the efficiency of the television?
- Pout / Pin
- (Pin − Pout) / Pin
- Pin / Pout
- Pout / (Pin − Pout)
Show answer and explanation
Answer: A. Pout / Pin
Efficiency is defined as useful output power divided by total input power, Pout/Pin.
May/June 2022 · Paper 1 · Work, energy and power
A box slides down a rough ramp from X to Y. The change in gravitational potential energy is 16 J. The box has 24 J of kinetic energy at X and 35 J of kinetic energy at Y. How much work is done against the frictional force?
- 5 J
- 19 J
- 27 J
- 43 J
Show answer and explanation
Answer: A. 5 J
Energy conservation: GPE lost + KE at X = KE at Y + work done against friction; 16 + 24 = 35 + W, so W = 5 J.
October/November 2022 · Paper 1 · Work, energy and power
A man of mass 75 kg runs up a staircase of 30 steps, each 20 cm high, taking 7.0 s.
What is the average rate of increase of gravitational potential energy of the man?
- 64 W
- 450 W
- 630 W
- 4400 W
Show answer and explanation
Answer: C. 630 W
Height gained = 30×0.20 = 6.0 m. Power = mgh/t = (75×9.81×6.0)/7.0 ≈ 630 W.
May/June 2021 · Paper 1 · Work, energy and power
A rocket is fired upwards. As it accelerates upwards after leaving the launch pad, which forms of energy are changing?
- chemical energy, gravitational potential energy and kinetic energy
- chemical energy and gravitational potential energy only
- chemical energy and kinetic energy only
- gravitational potential energy and kinetic energy only
Show answer and explanation
Answer: A. chemical energy, gravitational potential energy and kinetic energy
Fuel is burned (chemical energy decreases) while the rocket rises (gravitational PE increases) and speeds up (KE increases) — all three change.
