12. Assertion : Sterss is the internal force per unit area of a body. Reason : Rubber is less elastic than steel.

(a)        If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b)        If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c)        If assertion is true but reason is false.

(d)        If the assertion and reason both are false.

(e)        If assertion is false but reason is true.

Explanation-

(b) Stress is defined as internal force (restoring force) per unit area of a body. Also, rubber is less elastic than steel, because restoring force is less for rubber than steel.

(14)