A factory worker pushes a heavy crate along a flat floor at a steady speed. She applies a force of 250 N and moves the crate a distance of 8 m in 20 seconds. Explain what is meant by the terms 'work done' and 'power', and describe how each quantity would change if the same worker moved the same crate the same distance but in only 10 seconds, applying the same force.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A factory worker pushes a heavy crate along a flat floor at a steady speed. She applies a force of 250 N and moves the crate a distance of 8 m in 20 seconds. She then repeats the task, applying the same force over the same distance but in only 10 seconds.
Model answer (4 marks)
Work done is the product of the force applied and the distance over which it acts in the direction of the force – it is the energy transferred to the crate.
Power is the rate at which work is done, i.e. work divided by the time taken.
If the worker pushes the same 250 N force over the same 8 m, the work done remains unchanged.
Because the same work is now done in half the time, the power increases – it doubles.
Power is the rate at which work is done, i.e. work divided by the time taken.
If the worker pushes the same 250 N force over the same 8 m, the work done remains unchanged.
Because the same work is now done in half the time, the power increases – it doubles.
Examiner tips
- Define work as force × distance in the force direction; define power as work ÷ time.
- Show that work is unchanged because force and distance are unchanged.
- Show that power doubles because time halves.
- Use correct units (J for work, W for power).
Common mistakes
- Confusing work with force or distance alone.
- Calculating power as force × distance instead of work ÷ time.
- Forgetting to state that work is unchanged.
Mark scheme (4 marks)
- Work done is the product of the force and the distance moved in the direction of the force (or: work is done when a force moves an object through a distance)
- Power is the rate at which work is done (or: the rate at which energy is transferred)
- The work done would remain the same / unchanged, because the force and distance are the same
- The power would increase / double, because the same work is done in half the time
Key terms in this question
work done · power · force · distance · rate
Related
- All Pearson Edexcel International GCSE Physics (4PH1) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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