Explain why a rubber band is described as having elastic behaviour and describe what happens to the rubber band when a force greater than its elastic limit is applied.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A student stretches a rubber band by hanging weights from it. They notice that when small weights are removed, the rubber band returns to its original length. However, when a very large weight is added and then removed, the rubber band does not return to its original length.
Model answer (5 marks)
A rubber band is said to have elastic behaviour because when a force is applied it deforms but returns to its original length once the force is removed. The deformation is temporary and reversible, so the band recovers its shape. The elastic limit is the maximum force or extension at which this recovery still occurs. If a force greater than the elastic limit is applied, the deformation becomes permanent – the band no longer returns to its original length. After the large weight is removed the rubber band is left longer than its original length, having a new resting length.
Examiner tips
- Use the term "elastic behaviour" and explain recovery of shape
- Mention the elastic limit and that exceeding it causes permanent deformation
- State that the band ends up longer than its original length
Common mistakes
- Confusing elastic with plastic deformation terminology
- Failing to mention the elastic limit
- Saying the band simply stretches without noting the permanent change
Mark scheme (5 marks)
- Elastic behaviour means the material returns to its original shape/length after the force is removed
- This happens because the deformation is temporary / reversible
- The elastic limit is the maximum force/extension beyond which the material will not return to its original shape
- When the force exceeds the elastic limit, the deformation becomes permanent / inelastic
- The rubber band is now longer than its original length / has a new resting length after the large weight is removed
Key terms in this question
elastic behaviour · elastic limit
Related
- All AQA A-Level Physics (7408) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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