A solid sphere is rolled on a rough surface and it is found that sphere stops after some time.

Options

A. Friction decreases the linear speed
B. Torque of friction tries to increase the angular speed
C. Torque of normal reaction tries to decrease the angular speed
D. Normal reaction decreases the linear speed

Answer

A, B, C

Explanation

When sphere rolls on rough horizontal surface then friction acte opposite to motion and thus decreases linear speed of the sphere. But torque of friction is in the direction of angular velocity so it increases angular speed. Bodies are deformed and normal reaction gets shifted to apply torque opposite to angular velocity. This torque of normal reaction decreases angular speed. Moreover, normal reaction is vertical and cannot change linear speed. Hence options (a), (b) and (c) are correct.