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A2 Daily A Level Physics question

2026-05-04 OCR A Materials: brittle/ductile/polymeric (M3.4) OCR-A Module 3.4 Materials: mechanical properties (brittle, ductile, polymeric); interpretation of stress–strain graphs

Which statement must be true when a material is described as brittle in a standard tensile test at room temperature?

  1. A It fractures soon after the elastic limit is reached, showing negligible plastic deformation. (correct)
  2. B It undergoes large plastic strain and noticeable necking before fracture.
  3. C Its initial stress–strain gradient is small, so it stretches easily under small loads.
  4. D It can be stretched to several times its original length and returns fully on unloading.

Answer

The correct answer is A.

Correct: A — It fractures soon after the elastic limit is reached, showing negligible plastic deformation. A describes brittle behaviour: failure occurs with little or no plastic deformation once the elastic region ends. B describes ductile behaviour, where materials yield, neck and sustain large plastic strain before breaking. C confuses stiffness with brittleness; many brittle materials are stiff (large initial gradient) and not necessarily easy to stretch. D describes polymeric elastomers (e.g. rubber) with very large reversible strains, not brittle materials.

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