AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Required practical activity 6: investigate the relationship between force…
Full specification wording
Forces and elasticity: Required practical activity 6: investigate the relationship between force and extension for a spring.
Clamp a spring from a stand with the base weighted or clamped to the bench so it cannot topple.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 7 of 7
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Clamp a spring from a stand with the base weighted or clamped to the bench so it cannot topple. Measure the unstretched length with a millimetre rule held vertically alongside, reading the position of the bottom of the spring at eye level to avoid parallax error. Add weights one newton at a time, measuring the new length after each and subtracting the original unstretched length to calculate the extension. Take readings as the weights are removed to check they match, ensuring no inelastic deformation. Plot force on the vertical axis against extension on the horizontal; the gradient of the straight part is the spring constant. The control variable is the spring itself. The graph curving at the top shows the limit of proportionality.
What earns the marks
- Measuring the original unstretched length of the spring before any load is added.
- Adding known weights in equal steps and recording the new length each time.
- Calculating each extension as new length minus original length.
- Plotting force against extension and taking the gradient of the straight section.
Common mistakes and how to put them right
Holding the rule at an angle, which makes every measured length inaccurate.
Recording total lengths and plotting them as extensions without subtracting the initial length.
Loading the spring past its limit of proportionality and then including those points in the gradient calculation.
Leaving the clamp stand unsecured so that it tips as the load grows.
Exam tips
- Say eye level and rule vertical when asked how to reduce measurement error; both are credited.
- Describe repeating the readings as the load is removed, to check the spring has not been inelastically deformed.
Try the lesson
The start of the Forces and elasticity: Required practical activity 6: investigate the relationship between force and extension for a spring. lesson, made from checked teaching notes for this specification point.
Have a go first
In an experiment to investigate the relationship between force and extension for a spring, which piece of equipment is used to measure the extension of the spring?
Listen
Clamp a spring from a stand with the base weighted or clamped to the bench so it cannot topple. Measure the unstretched length with a millimetre rule held vertically alongside, reading the position of the bottom of the spring at eye level to avoid parallax error. Add weights one newton at a time, measuring the new length after each and subtracting the original unstretched length to calculate the extension. Take readings as the weights are removed to check they match, ensuring no inelastic deformation. Plot force on the vertical axis against extension on the horizontal; the gradient of the straight part is the spring constant. The control variable is the spring itself. The graph curving at the top shows the limit of proportionality. A strong answer earns marks for these points. measuring the original unstretched length of the spring before any load is added. adding known weights in equal steps and recording the new length each time. calculating each extension as new length minus original length. plotting force against extension and taking the gradient of the straight section. Exam tip: Say eye level and rule vertical when asked how to reduce measurement error; both are credited.
Key words
Say what each word means before you turn the card.
parallax error
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extension
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force-extension graph
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limit of proportionality
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See every definition
- parallax error
- Reading the position of the bottom of the spring at eye level avoids this error when the millimetre rule is held vertically alongside.
- extension
- Calculated by subtracting the original unstretched length from the new length measured after each weight is added.
- force-extension graph
- A plot of force on the vertical axis against extension on the horizontal, whose gradient of the straight part is the spring constant.
- limit of proportionality
- Shown by the graph curving at the top.
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