question_answer

Direction for: In each of the following questions a statement of Assertion is given followed by a corresponding statement of Reason just below it. Of the statements mark the correct answer as

Assertion: The acceleration of a body down a rough inclined plane is greater than the acceleration due to gravity. Reason: The body is able to slide on a inclined plane only when its acceleration is greater than acceleration due to gravity.

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 the Reason is not the correct explanation of the Assertion

C)  If Assertion is true but Reason is false

D)  If both Assertion and Reason are false

Correct Answer: D

Solution :

Let a body which has mass m is placed inclined plane whose inclination is greater than angle of repose. The force on the body down the inclined plane is given by \[F=mg\,\sin \theta -\mu R\] \[ma=mg\,\sin \theta -\mu mg-\mu mg\cos \theta \] or      \[a=g\,\sin \theta -\mu g\cos \theta \] \[=g(\sin \theta -\mu cos\theta )\]       ??.(i) It is obvious from Eq. (i) that \[a<g\]