Describe what happens to a spring when it is loaded with increasing force, from the point where it obeys Hooke's Law up to the point where it undergoes plastic deformation.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
The extension of a spring is directly proportional to the force applied – this is Hooke’s Law. This linear relationship continues up to the limit of proportionality. Beyond this point the extension is no longer proportional to the force. If the force is removed before the elastic limit is reached, the spring returns to its original shape and length (elastic deformation). Once the elastic limit is exceeded the spring undergoes plastic deformation and will not return to its original shape or length when the force is removed.
Examiner tips
- Use the phrase ‘directly proportional’ to show Hooke’s Law.
- Mention the ‘limit of proportionality’ and ‘elastic limit’ as key terms.
- Show the change from elastic to plastic deformation clearly.
Common mistakes
- Confusing ‘elastic limit’ with ‘limit of proportionality’.
- Saying the spring ‘stops working’ instead of ‘does not return to original shape’.
- Omitting the proportional relationship in the first part.
Mark scheme (4 marks)
- The extension is directly proportional to the force applied (Hooke's Law is obeyed)
- This continues up to the limit of proportionality, beyond which extension is no longer proportional to force
- If the force is removed before the elastic limit is reached, the spring returns to its original shape/length (elastic deformation)
- Beyond the elastic limit, the spring undergoes plastic deformation and will not return to its original shape/length when the force is removed
Key terms in this question
Hooke's Law · plastic deformation
Related
- All AQA GCSE Physics (8463) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
More Forces and elasticity questions
- A student presses down on a foam cushion and then removes the force. The foam re…
- A student stretches a rubber band and then releases it. The rubber band returns …
- A bungee rope is used to store elastic potential energy during a jump. Explain h…
- Explain why a spring that has been stretched beyond its elastic limit will not r…