Question 1 (2 marks)
Calculation
Spring length changes from 8.0 cm to 12.5 cm. Find extension.
Show model answer / marking points
12.5 − 8.0 = 4.5 cm (2).
Required Practical 18: Force and Extension | AQA GCSE Science | The Science Department
About this practical and its aim
Aim
Investigate the relationship between force applied to a spring and its extension.
Introduction
There is an obvious link between the force acting on a spring and the amount that is extends. Here, you get to measure it, plot your results, see if you have passed the limit of proportionality (elastic limit) and calculate the spring constant as well as how much energy is in the elastic potential energy store at each point.
The science behind the practical
Within the limit of proportionality, force and extension are directly proportional (Hooke’s law).
Key things to remember
Measure original length; add masses safely; convert masses to weights; measure extension each time.
Equipment and apparatus
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Clamp stand
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spring
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mass hanger
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slotted masses
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ruler
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pointer
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safety tray or catch
Method: How to carry out the experiment
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Collect the equipment to set up the apparatus below
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Note how far the bottom of the spring reaches onto the ruler by the side and record this as 0 kg added
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Add the first mass (this is the actual hook part of the masses) and record the mass (g) and the new height for the bottom of the spring
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Add a mass to the mass hanger and record the new total mass and the new height.
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Continue until you have added all the masses as instructed by your teacher, do not overload the spring.
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Construct a table showing: mass added (g), force applied (N), length (m), extension (m).
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Finally plot a graph to show Extension (X-axis) against Force (Y - Axis)
Variables and fair testing
| Type of variable | What is measured or controlled? |
|---|---|
| Independent variable | Applied force (N) |
| Dependent variable | Extension (m or cm) |
| Control variables | Same spring; starting length; ruler position; equipment temperature |
Safety and managing risks
Follow your teacher's instructions and your school's risk assessment. This page is not a substitute for a formal risk assessment.
| Hazard | Risk | Precaution |
|---|---|---|
Stretched spring or falling masses |
Eye injury or impact |
Do not overload spring; keep faces clear and use a catch tray. |
Clamp stand |
Falling equipment |
Check clamp stability before adding weights. |
Results, calculations and analysis
Recording, presenting and interpreting results
Table: force (N), total length (cm), extension (cm). Plot force against extension; find gradient in proportional region.
Calculations
Extension = new length − original length; F = ke; weight = mg.
Conclusions, accuracy and evaluation
Drawing a conclusion
Extension rises linearly with force up to the limit of proportionality.
Evaluating the investigation
Use repeats and avoid exceeding the elastic limit; ensure ruler zero and spring are aligned.
More to learn
Limit of proportionality
Up to the limit of proportionality, a plot of force against extension is a straight line through the origin.
Common exam mistake
Extension is new length minus original length, not the new total length.
GCSE examination practice
Answer each question in full before opening the model answer. Check your work against the marking points and look for scientific key words.
Question 2 (2 marks)
Knowledge
State Hooke’s law within the limit of proportionality.
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Force is directly proportional to extension (1), F = ke (1).
Question 3 (1 marks)
Analysis
What does a curved region on a force-extension graph suggest?
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The spring has passed the limit of proportionality (1).
Question 4 (2 marks)
Evaluation
Suggest one improvement to make the investigation more reliable and explain why it helps.
Show model answer / marking points
Repeat measurements and calculate a mean (1), reducing the influence of random variation/anomalies (1). Alternative valid improvement specific to the experiment with explanation can gain both marks.
This page was updated on: 24th June 2026