The Physics Question Bank

Course: Combined Science + Separate Physics  |  Tier: Foundation + Higher  |  Equation sheet: given in the exam

The equation

power = work done ÷ time    P = W / t

Quantity	Symbol	Unit
power	P	watts
work done	W	joules (J)
time	t	seconds (s)

Rearranged: W = P × t  |  t = W ÷ P

Use FIFA for every answer

• F – Formula: write the equation as it appears on the sheet.
• I – Insert: put in the numbers (convert to standard units first).
• F – Fix: rearrange to make the unknown the subject.
• A – Answer: calculate and always give the unit.

Foundation: aim for Q1–8.   Higher: aim for Q4–10. Most questions need rearranging.

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Questions

Q1 (F) A student does 1200 J of work running up the stairs in 6 s. Calculate her power.

Show solution

F: P = W / t
I: P = 1200 ÷ 6
F: P is already the subject
A: 200 W

Q2 (F) A cyclist works at 300 W for 60 s. Calculate the work done.

Show solution

F: P = W / t
I: 300 = W ÷ 60
F: W = 300 × 60
A: 18 000 J

Q3 (F) A 500 W electric motor on a conveyor belt does 10 000 J of work. How long does this take?

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F: P = W / t
I: 500 = 10 000 ÷ t
F: t = 10 000 ÷ 500
A: 20 s

Q4 (F) A 1.2 kW winch on a boat does 36 kJ of work. How long does this take?

Show solution

Convert first: 1.2 kW = 1200 W; 36 kJ = 36 000 J
F: P = W / t
I: 1200 = 36 000 ÷ t
F: t = 36 000 ÷ 1200
A: 30 s

Q5 (F) A rower on a rowing machine works at 250 W for 20 minutes. Calculate the work done in kJ.

Show solution

Convert first: 20 minutes = 1200 s
F: P = W / t
I: 250 = W ÷ 1200
F: W = 250 × 1200 = 300 000 J
A: 300 kJ

Q6 (F/H) A crane’s 15 kW motor does 450 kJ of work lifting steel beams. How long does this take?

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Convert first: 15 kW = 15 000 W; 450 kJ = 450 000 J
F: P = W / t
I: 15 000 = 450 000 ÷ t
F: t = 450 000 ÷ 15 000
A: 30 s

Q7 (F/H) A car engine produces 30 kW. How much work does it do in 40 s? Give your answer in kJ.

Show solution

Convert first: 30 kW = 30 000 W
F: P = W / t
I: 30 000 = W ÷ 40
F: W = 30 000 × 40 = 1 200 000 J
A: 1200 kJ

Q8 (F/H) A rocket engine produces 4.0 × 10⁹ W for 1.5 × 10² s. Calculate the work done.

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F: P = W / t
I: 4.0 × 10⁹ = W ÷ 1.5 × 10²
F: W = 4.0 × 10⁹ × 1.5 × 10²
A: 6.0 × 10¹¹ J

Q9 (H) A 60 kg student with a power of 480 W runs up stairs 4.0 m high. How long does it take? (g = 9.8 N/kg)

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Step 1 – work done lifting herself: W = m g h = 60 × 9.8 × 4.0 = 2352 J
Step 2 – time
F: P = W / t
I: 480 = 2352 ÷ t
F: t = 2352 ÷ 480
A: 4.9 s

Q10 (H) A horse pulls a cart with a steady force of 650 N while working at 900 W. How far does it pull the cart in 2.5 minutes? Give your answer to 2 significant figures.

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Convert first: 2.5 minutes = 150 s
Step 1 – work done
F: P = W / t
I: 900 = W ÷ 150
F: W = 900 × 150 = 135 000 J
Step 2 – distance
F: W = F s
I: 135 000 = 650 × s
F: s = 135 000 ÷ 650 = 207.7… m
A: 210 m (2 s.f.)