Free A.3 Work, energy & power questions for IB Physics (SL & HL), part of A Space, time & motion. Each question has the answer and the marking points an examiner would look for.
Generate a full A.3 Work, Energy & Power worksheet →All A Space, time & motion questionsA satellite moves at constant speed in a circular orbit. Which statements are correct?
I. The kinetic energy of the satellite is constant.
II. The gravitational force does no work on the satellite.
III. The acceleration of the satellite is directed towards the centre of the orbit.
Answer: D
A cyclist moves at a constant speed of 7.5 m s−1 against a total resistive force of 60 N.
What is the useful power output of the cyclist?
Answer: B
The air resistance on a car is given by F = cv2, where c = 0.35 in SI units. The maximum useful power output of the engine is 60 kW.
State the fundamental SI units of c.
Determine the maximum speed of the car on a level road.
Calculate the energy dissipated by air resistance when the car travels 1.0 km at this speed.
The efficiency of the engine is 30% and the energy density of the fuel is 34 MJ per litre. Calculate the volume of fuel used per kilometre at maximum speed.
Outline why the maximum speed increases only slightly when the engine power is doubled.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | kg m−1 F in kg m s−2 and v2 in m2 s−2 ✓ c in kg m−1 ✓ | 2 |
| (b) | 56 m s−1 P = Fv = cv3 ✓ v = 56 m s−1 ✓ | 2 |
| (c) | 1.1 × 106 J W = cv2 × 1000 ✓ = 1.1 × 106 J ✓ | 2 |
| (d) | 0.11 L fuel energy = 3.6 × 106 J ✓ V = 0.11 L ✓ | 2 |
| (e) | v ∝ P1/3 v ∝ P1/3, so doubling P increases v by only 26% ✓ | 1 |
A bungee jumper of mass 80 kg falls from rest from a platform. The unstretched cord has length 15 m and obeys Hooke’s law with spring constant 80 N m−1. Air resistance and the mass of the cord are negligible.
Calculate the speed of the jumper when the cord just becomes taut.
Show that the maximum extension x of the cord satisfies ½kx2 = mg(L + x), where L is the unstretched length, and hence determine x.
Determine the maximum speed of the jumper.
Calculate the maximum acceleration of the jumper and comment on its value.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 17.2 m s−1 mgh = ½mv2 ✓ v = √2 × 9.81 × 15 = 17.2 m s−1 ✓ | 2 |
| (b) | 29.6 m at the lowest point the KE is zero ✓ loss of GPE = mg(L + x) = gain in elastic PE ½kx2 ✓ 40x2 − 785x − 11772 = 0 ✓ x = 29.6 m ✓ | 4 |
| (c) | 19.8 m s−1 maximum speed when the resultant force is zero: extension = mgk = 9.81 m ✓ ½mv2 = mg(L + 9.81) − ½k(9.81)2 ✓ v = 19.8 m s−1 ✓ | 3 |
| (d) | 19.8 m s−2 a = kx − mgm = 19.8 m s−2 upwards ✓ about 2.01g, which may be dangerous ✓ | 2 |
A wind turbine has blades of length 20 m. Wind of speed 10 m s−1 passes through the turbine. The density of air is 1.2 kg m−3.
Show that the power available in the wind is about 750 kW.
The electrical output is 300 kW. Calculate the efficiency.
Calculate the power available when the wind speed halves.
Explain why a turbine can never extract all of the kinetic energy of the wind.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 754 kW P = ½ρAv3 ✓ = 0.5 × 1.2 × π × 202 × 103 = 7.5 × 105 W ✓ | 2 |
| (b) | 40 % 300/754 = 0.40 ✓ | 1 |
| (c) | 94 kW P ∝ v3 ✓ 754/8 = 94 kW ✓ | 2 |
| (d) | air must keep moving the air must still have kinetic energy to move away from the turbine ✓ and there are frictional/electrical losses ✓ | 2 |
A pump lifts water from a well 25 m deep at a rate of 8.0 kg s−1. The water leaves the pipe at 4.0 m s−1.
Calculate the rate at which gravitational potential energy is gained.
Calculate the rate at which kinetic energy is gained.
The pump’s input power is 3.0 kW. Calculate its efficiency.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | 1960 W mgh per second = 8.0 × 9.8 × 25 ✓ 1960 W ✓ | 2 |
| (b) | 64 W ½ × 8.0 × 4.02 = 64 W ✓ | 1 |
| (c) | 68% (1960 + 64) ÷ 3000 ✓ 67–68% ✓ | 2 |
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Meet Riyaz →Original IB-style practice questions written for mentorriyaz.in. These are not IB past paper questions, and this site is not affiliated with or endorsed by the International Baccalaureate Organization. Updated 2026-11-04. Paper generator · mentorriyaz.in