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Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : The property of a body by virtue of which it tends to regain its original shape when the external force is removed is elasticity. Reason (R) : The restoring force depends upon the bonded interatomic and intermolecular forces of the solid. In the light of the above statements, choose the correct answer from the options given below.

Asked in JEE Main 27th Jan 2nd Shift 2024 · Stress and strain

• (1) Both (A) and (R) are true but (R) is not the correct explanation of (A).
• (2) Both (A) and (R) are true and (R) is the correct explanation of (A).
• (3) (A) is true but (R) is false.
• (4) (A) is false but (R) is true.

Step-by-step solution

Why the other options are wrong

• (1) comes from treats the two statements as unrelated facts; but the interatomic bonds named in (R) are the actual source of the restoring force, which is the whole content of (A).
• (3) comes from calls (R) false, usually from thinking of elasticity as a bulk property only; the restoring force in a stretched solid is the sum of the interatomic forces resisting the increased separation.
• (4) comes from calls (A) false, perhaps by confusing elasticity with plasticity; a body that does not regain its shape is plastic, and (A) is the standard definition of elasticity.

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