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Forces and elasticity
This topic develops the force-extension relationship through practical measurement, graph interpretation and elastic potential energy calculations.
42
Objectives
210
Flashcards
210
Questions
90 min
Study time
AQAGCSEPhysicsForces
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42 objective pages available
Stretching and deformation10 objectives
- Define elastic deformation as deformation that is reversed when the force is removed.
- Define inelastic deformation as deformation that is not fully reversed when the force is removed.
- Describe extension as the increase in length of an object when stretched.
- Describe compression as deformation caused by squeezing forces.
- Explain that a force can stretch, compress or bend an object.
- Identify the limit of proportionality on a force-extension graph.
- Describe what happens when an object is stretched beyond the limit of proportionality.
- Distinguish extension from total length in practical measurements.
- Explain why measurements should be repeated when investigating extension.
- Apply WS 2.2, WS 2.3 and WS 3.5 skills when planning and evaluating extension investigations.
Hooke's law and spring constant11 objectives
- State that extension is directly proportional to force up to the limit of proportionality.
- Use the equation force = spring constant x extension.
- Calculate force from spring constant and extension.
- Calculate spring constant from force and extension.
- Calculate extension from force and spring constant.
- State that spring constant is measured in newtons per metre.
- Interpret spring constant as a measure of stiffness.
- Determine spring constant from the gradient of a force-extension graph.
- Identify when Hooke's law no longer applies from a force-extension graph.
- Convert extension between centimetres and metres where required.
- Apply MS 3b, MS 3c and MS 4a skills when using or graphing F = ke.
Required practical: force and extension11 objectives
- Describe how to measure the original length of a spring before adding loads.
- Describe how to add known loads to a spring safely and measure its new length.
- Calculate extension by subtracting original length from stretched length.
- Record force and extension measurements in a suitable table.
- Plot a force-extension graph using appropriate scales and units.
- Use the straight-line section of a force-extension graph to identify proportional behaviour.
- Determine spring constant from the gradient of the linear section of the graph.
- Identify anomalous readings in force-extension data.
- Explain why the spring should not be overloaded beyond its elastic limit.
- Evaluate sources of uncertainty in force and extension measurements.
- Apply WS and MS skills when drawing graphs, finding gradients and evaluating repeatability.
Elastic potential energy10 objectives
- Describe elastic potential energy as energy stored in a stretched or compressed elastic object.
- Use the equation elastic potential energy = 0.5 x spring constant x extension squared.
- Calculate elastic potential energy from spring constant and extension.
- Identify extension in metres when using the elastic potential energy equation.
- Explain why doubling extension more than doubles elastic potential energy.
- Link work done in stretching a spring to elastic potential energy stored.
- Distinguish force-extension calculations from elastic potential energy calculations.
- Explain why the equation applies within the elastic behaviour of the spring.
- Apply MS 3b and MS 3c skills when calculating elastic potential energy.
- Interpret force-extension graphs in terms of energy stored where appropriate.
Key terms
Elastic DeformationInelastic Deformationinelastic deformationelastic deformationextensiondeformationcompressionlimit of proportionalitytotal lengthHooke's LawSpring Constantspring constant
Exam tips
- Understand Elastic Deformation: Use the named force or motion quantity when you clearly define elastic deformation as the reversible change in shape of an object when the applied force is removed. Link your answer to Stretching and deformation and keep elastic and plastic deformation separate.
- Understand Inelastic Deformation: Use the named force or motion quantity when you clearly define inelastic deformation in your own words, emphasizing that it does not fully reverse when the force is removed. Link your answer to Stretching and deformation and keep elastic and plastic deformation separate.
Common mistakes
- Confusing Elastic and Inelastic Deformation: Remember that elastic deformation is when the object returns to its original shape after the force is removed, while inelastic deformation does not fully reverse.
- Misunderstanding Inelastic Deformation: Emphasize that inelastic deformation does not fully return to the original shape when the force is removed, unlike elastic deformation which does.
Practice preview
- Which option best applies elastic deformation for Stretching and deformation in AQA GCSE Physics Forces?
- When a spring is stretched and then released, the spring returns to its original length. This behaviour is an example of:
- A rubber band that keeps its shape after being stretched is an example of a material that exhibits
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