A spring is stretched beyond its limit of proportionality. Explain what this means for the relationship between the load applied and the extension of the spring, and state what happens to the spring when the load is removed.

Cambridge International IGCSE Physics (0625) — 1.5 Forces · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Beyond the limit of proportionality the extension is no longer directly proportional to the load applied.
The spring constant no longer applies – the load–extension graph is no longer a straight line through the origin.
When the load is removed the spring does not return to its original shape or length.
The spring is no longer behaving as an elastic solid – the deformation is permanent (inelastic).

Examiner tips

  • Use the phrase "beyond the limit of proportionality" early. Show the change from a straight line to a curved or broken graph. Mention permanent deformation when the load is removed. Keep answer concise – 4 points, one sentence each.

Common mistakes

  • Confusing the limit of proportionality with the elastic limit. Saying the spring returns to its original shape. Using vague terms like "non‑linear" without linking to permanent change.

Mark scheme (4 marks)

  1. Beyond the limit of proportionality, extension is no longer directly proportional to the load applied
  2. The spring constant no longer applies / the load–extension graph is no longer a straight line through the origin
  3. The spring does not return to its original shape/length when the load is removed
  4. The spring is no longer behaving as an elastic solid / the deformation is permanent (inelastic)

Key terms in this question

limit of proportionality · extension

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