JEE Main 2024 — 27 January, Shift 2 — Question 44

Let's analyze the Assertion (A) and 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.

Elasticity: This is precisely the definition of elasticity. It is the ability of a material to deform reversibly when subjected to a stress and to return to its original shape and size when the stress is removed.

Therefore, Assertion (A) is True.

Reason (R): The restoring force depends upon the bonded inter atomic and inter molecular force of solid.

Restoring Force: When a material is deformed, internal forces arise within the material that oppose the deformation and try to restore the material to its original shape. These are called restoring forces.

Origin of Restoring Force: In solids, atoms or molecules are held together by interatomic and intermolecular forces (like covalent bonds, ionic bonds, metallic bonds, or van der Waals forces). When an external force deforms the material, these bonds are stretched or compressed from their equilibrium positions. The restoring forces originate from the tendency of these bonds to return to their equilibrium distances and angles.

Therefore, Reason (R) is True.

Relationship between A and R:

Reason (R) explains why a body exhibits elasticity (A). The macroscopic property of elasticity (A) arises from the microscopic interatomic and intermolecular forces (R) that generate the restoring forces. When these forces pull the atoms/molecules back to their original positions, the body regains its shape.

Therefore, both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation for Assertion (A).

The final answer is A​