Elastic and plastic behaviour
Cambridge A-Level Physics (9702) · Unit 6: Deformation of solids · 7 flashcards
Elastic and plastic behaviour is topic 6.2 in the Cambridge A-Level Physics (9702) syllabus , positioned in Unit 6 — Deformation of solids , alongside Stress and strain. In one line: Elastic deformation is a temporary change in shape of a material when a stress is applied, and the material returns to its original shape when the stress is removed.
Marked as AS Level: examined at AS Level in Paper 1 (Multiple Choice), Paper 2 (AS Structured Questions) and Paper 3 (Advanced Practical Skills). The same content may also be assumed in Paper 4 (A Level Structured Questions).
The deck below contains 7 flashcards — 3 definitions, 2 key concepts and 2 calculations — covering the precise wording mark schemes reward. Use the 3 definition cards to lock down command-word answers (define, state), then move on to the concept and calculation cards to handle explain, describe, calculate and compare questions.
'elastic deformation'
Elastic deformation is a temporary change in shape of a material when a stress is applied, and the material returns to its original shape when the stress is removed.
What the Cambridge 9702 syllabus says
2025-2027 syllabus, in our words · AS LevelWhat the syllabus expects you to be able to do in this topic, in plain English. For the exact wording, see the official syllabus (PDF).
- Understand the meanings of elastic limit, elastic deformation and plastic deformation, and use these terms.
- Understand that the work done is given by the area under a force-extension graph.
- Use the area beneath a force-extension graph to find how much elastic potential energy is stored in a material stretched or compressed no further than its limit of proportionality.
- Recall Ep = ½Fx = ½kx² and use it for a material whose deformation stays within the limit of proportionality.
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 9702 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Tips to avoid common mistakes in Elastic and plastic behaviour
- › Memorize that the area under a force-extension graph is energy, while the area under stress-strain is energy per unit volume.
- › Apply the relationship Eₚ ∝ x²; recognize that doubling the extension quadruples the energy because the tension also doubles as extension increases.
- › Always define the area under a force-extension graph as 'work done' in stretching the material, regardless of whether the deformation is elastic or plastic.
Define 'elastic deformation'.
Elastic deformation is a temporary change in shape of a material when a stress is applied, and the material returns to its original shape when the stress is removed.
Define 'plastic deformation'.
Plastic deformation is a permanent change in shape of a material when a stress is applied, and the material does not return to its original shape when the stress is removed.
Define 'elastic limit'.
The elastic limit is the maximum stress that a solid material can withstand before undergoing permanent deformation. Beyond this limit, the material will be plastically deformed.
What does the area under a force-extension graph represent?
The area under a force-extension graph represents the work done in deforming the material. If the deformation is elastic (up to the elastic limit), this work is stored as elastic potential energy and is recovered when the load is removed.
State the formula for elastic potential energy (EP) in terms of force and extension, when within the limit of proportionality.
EP = (1/2) * F * x, where F is the applied force and x is the extension. This formula applies only within the material's limit of proportionality (Hooke's Law).
State the formula for elastic potential energy (EP) in terms of the spring constant and extension, when within the limit of proportionality.
EP = (1/2) * k * x², where k is the spring constant and x is the extension. This formula applies only within the material's limit of proportionality (Hooke's Law).
How can you determine the elastic potential energy stored in a spring from a force-extension graph?
The elastic potential energy is equal to the area under the force-extension graph, up to the point of extension considered. This area can be calculated using geometry (
Review the material
Read full revision notes on Elastic and plastic behaviour — definitions, equations, common mistakes, and exam tips.
Read NotesMore topics in Unit 6 — Deformation of solids
Elastic and plastic behaviour sits alongside these A-Level Physics decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Key terms covered in this Elastic and plastic behaviour deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
How to study this Elastic and plastic behaviour deck
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