Curriculum fit: GCSE Physics and Combined Science (energy; forces). US: middle and high school physical science (energy and work).
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What Is It?
Work is done when a force makes something move. The more force you use, or the further the object moves, the more work is done. The work done equals the energy transferred.
Power tells you how fast work is done or energy is transferred. A more powerful machine transfers the same energy in less time.
Key Formulas and Ideas
- Work done W = force × distance moved in the direction of the force (W = Fs). Unit: joule (J).
- Power P = work done ÷ time = energy transferred ÷ time. Unit: watt (W), where 1 W = 1 J/s.
- Electrical power P = V × I.
Worked Examples
Work Done
A 50 N force pushes a box 4 m. Find the work done.
- W = F × s.
- = 50 × 4 = 200.
✓ Answer 200 J
Power
A motor does 600 J of work in 20 s. Find its power.
- P = W ÷ t.
- = 600 ÷ 20 = 30.
✓ Answer 30 W
Lifting
Find the work done lifting a 10 kg load through 3 m (g = 9.8 N/kg).
- Weight = 10 × 9.8 = 98 N.
- W = 98 × 3 = 294.
✓ Answer 294 J
Common Mistakes to Avoid
- Forgetting that distance must be in the direction of the force.
- Mixing up work (J) and power (W).
- Using the mass instead of the weight as the force.
- Not converting minutes to seconds.
Practice Questions
Frequently Asked Questions
Is work done when you hold a heavy bag still?
In physics no work is done on the bag, because it does not move, even though your muscles get tired.
What does 1 watt mean?
One joule of energy transferred each second.
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KS3GCSEMiddle SchoolHigh SchoolSources and Review
Reviewed by StudyMorrow editorial review on 5 Nov 2026.