question_answer

The given figure shows a ball rolling down an inclined plane. The direction of motion of the ball is represented by arrow I. Arrows II and III respectively represent the directions of

A)  Rolling frictional force and gravitational force

B)  Gravitational force and normal reaction

C)  Rolling frictional force and air friction

D)  Air friction and normal reaction

Correct Answer: C

Solution :

  Friction plays an important role in the motion of an object. When a ball is rolled down an inclined plane, the rolling friction opposes its motion. Also, when an object moves through air, air friction (also called air drag) opposes its motion. The following figure shows the names and directions of forces acting on the rolling ball. Hence, arrows II and III respectively represent the directions of the rolling frictional force and air friction acting on the ball. The correct answer is C.