AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
A force that stretches (or compresses) a spring does work and elastic…
Full specification wording
Forces and elasticity: A force that stretches (or compresses) a spring does work and elastic potential energy is stored in the spring.
Stretching or compressing a spring means moving its end through a distance against the spring's force, so the applied force does work and that work fills the spring's elastic potential energy store.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 4 of 7
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Stretching or compressing a spring means moving its end through a distance against the spring's force, so the applied force does work and that work fills the spring's elastic potential energy store. The store depends on the square of the extension or compression, so doubling the deformation stores four times the energy. That is why pulling a toy launcher back twice as far sends it much further, and why compressing a suspension spring twice as much absorbs four times the energy. When the spring is released the elastic store empties into whatever it pushes: the kinetic store of a launched aeroplane, or the gravitational potential store of a pod rising on bungee cords. In practice not all of it arrives, because air resistance and internal heating take a share.
What earns the marks
- Stating that the stretching or compressing force does work on the spring.
- That work filling the elastic potential energy store.
- The store depending on the square of the extension or compression, so doubling it stores four times as much.
- The elastic store emptying into the kinetic or gravitational potential store on release.
Common mistakes and how to put them right
Saying the energy stored is proportional to the extension or compression rather than to its square.
Writing that force is stored in the spring instead of energy.
Claiming all the elastic energy becomes kinetic energy, ignoring air resistance and heating.
Put it right: Account for efficiency losses.
Forgetting that compressing a spring also stores elastic potential energy.
Put it right: The principle applies to both stretching and compressing.
Exam tips
- If the extension or compression doubles, write four times before reaching for the calculator - it is often all the mark needs.
- Say where the energy goes on release; 'it is released' is not an energy transfer.
Try the lesson
The start of the Forces and elasticity: A force that stretches (or compresses) a spring does work and elastic potential energy is stored in the spring. lesson, made from checked teaching notes for this specification point.
Have a go first
A student pulls a spring so that it gets longer. What is stored in the stretched spring because a force has done work on it?
Listen
Stretching or compressing a spring means moving its end through a distance against the spring's force, so the applied force does work and that work fills the spring's elastic potential energy store. The store depends on the square of the extension or compression, so doubling the deformation stores four times the energy. That is why pulling a toy launcher back twice as far sends it much further, and why compressing a suspension spring twice as much absorbs four times the energy. When the spring is released the elastic store empties into whatever it pushes: the kinetic store of a launched aeroplane, or the gravitational potential store of a pod rising on bungee cords. In practice not all of it arrives, because air resistance and internal heating take a share. A strong answer earns marks for these points. stating that the stretching or compressing force does work on the spring. that work filling the elastic potential energy store. the store depending on the square of the extension or compression, so doubling it stores four times as much. the elastic store emptying into the kinetic or gravitational potential store on release. Exam tip: If the extension or compression doubles, write four times before reaching for the calculator - it is often all the mark needs.
Key words
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elastic potential energy
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work done on a spring
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compression and extension
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energy transfer on release
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See every definition
- elastic potential energy
- The energy stored in a spring when a force stretches or compresses it.
- work done on a spring
- The result of a force moving the end of a spring through a distance against the spring's force.
- compression and extension
- The deformation of a spring, either squashed or stretched, on whose square the stored energy depends.
- energy transfer on release
- The emptying of the elastic store into whatever the spring pushes, such as a kinetic or gravitational potential store.
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