Work Done (OCR GCSE Physics A, Combined (Gateway Science Suite)): Revision Notes
📚 Revision Notes
5.2.1 Work Done
Work done
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Formula
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Key Points
- Where Work Done, , is in joules , the force, , is in newtons (N), and the distance, , is in metres .
- Where distance is the distance moved along the line of action of the force.
Definition
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Work done is when energy is transferred from the object doing the work to another form.
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Examples:
- If a book is lifted 1m in the air and 2m to the right.
- Work is done (against gravity) when moving 1m vertically, as that is in the direction of the force (gravity).
- Energy is transferred from your muscles to the book, increasing its gravitational potential.
Joules
- One joule of work is done when a force of one newton causes a displacement of one metre.
Friction
- Work done against frictional forces causes a rise in temperature of the object.
Work Done in a Spring
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Formula
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Key Points
- When a force stretches or compresses a spring, the spring does work.
- Elastic potential energy is stored in the spring.
- Provided it does not inelastically deform:
- The work done on the spring equals the elastic potential energy stored.
Calculating Work Done
The amount of work done on an object due to a force can be calculated using the following equation:
- is work done in Joules (J)
- is force in Newtons, (N)
- is the distance in metres (m).
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1J of work is done when a force of 1N moves an object through a distance of 1m. Therefore 1 Joule = 1 Newton-meter.
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Example: Calculating Work Done A man pushes a box through a distance of 12m, and he exerts 14N of force on the box. Calculate the work done by the man. Ignore the frictional force.
[2 marks]
Using the work done equation:
Substitute in the values:
=14×12
Calculate the answer:
=168J or Nm