JEE Main 2024 · 27 January · evening · Single correct · +4 / −1
Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : The property of 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 inter atomic and inter molecular force of solid.
In the light of the above statements, choose the correct answer from the options given below :
- (a) (A) is false but (R) is true
- (b) Both (A) and (R) are true but (R) is not the correct explanation of (A)
- (c) Both (A) and (R) are true and (R) is the correct explanation of (A)
- (d) (A) is true but (R) is false
Answer and solution
Answer (c) Both (A) and (R) are true and (R) is the correct explanation of (A)
Solution
Physics sir · 4 steps
Ask what pulls the body back when you let go: the bonds between its atoms. That is why R explains A.
- Check Assertion. Elasticity is defined as the property of a body by which it tends to regain its original shape and size once the deforming force is removed. So (A) is true.
- Check Reason. When a solid is deformed, its atoms are pushed closer or pulled apart from their equilibrium positions. The interatomic and intermolecular forces then act to bring them back, and this is the restoring force. So (R) is true.
- Link them. A body can regain its shape only because some force pulls it back. That restoring force comes from the bonds between atoms and molecules, so (R) tells you why elasticity exists at all.
- So. Both statements are true and (R) correctly explains (A). The answer is (c).
The idea to keep. In assertion-reason questions, ask whether R gives the cause of A. Elasticity always comes back to interatomic forces acting as restoring forces.
Answer from the NTA final answer key. Solution by PrepWiser.