question_answer

A ball is rolled upward along an inclined plane. After reaching a certain height from the ground, it rolls down along the plane. During the motion of the ball along the inclined plane, the force of friction

A)  Always opposes the motion

B)  Always facilitates the motion

C)  First opposes and then facilitates the motion

D)  First facilitates and then opposes the motion

Correct Answer: A

Solution :

  The friction between two surfaces always opposes the relative motion of the surfaces. When the ball moves upward along the inclined plane, frictional force acts downward. Similarly, when the ball rolls down, the force of friction acts upward. In both the cases, friction opposes the motion of the ball, as shown in the given figure. The correct answer is A.