Question

It is difficult to move cycle while applying brakes because
A. Rolling friction opposes motion on road
B. Sliding friction opposes motion on road
C. Rolling friction is more than the sliding friction
D. Sliding friction is more than rolling friction

Answer 1

Hint: When the brakes are applied to a moving cycle, then the rolling motion of the wheels stops and now only sliding motion is possible for the wheels. Since there is no rolling possible during brakes, no rolling friction will come into action.

Complete step by step answer:
When a cycle is moving then its wheels roll on the road. The friction which comes into action when a rolling motion occurs is known as the rolling friction. In the case of a cycle, this rolling friction is present only when the cycle is moving.
When brakes are applied on a moving cycle, the rolling motion of the cycle comes to a stop and due to absence of rolling, there will be no rolling friction acting on the cycle. But now sliding friction comes into action as after applying brakes only sliding motion is possible for the wheels of the cycle. This sliding friction opposes the motion of the cycle on the road.
Hence, based on the above discussion, the correct answer is option B. It is difficult to cycle while applying brakes because sliding friction opposes motion on the road.

Note:
It should be noted that the magnitude of the sliding friction is much greater than that of the rolling friction. Rolling friction comes into action during motion of cycle and there is not much obstruction to motion due to this friction. But in the case of sliding friction, very less motion is possible which requires much more force to move the cycle than in case of rolling friction. In case, if the rolling is perfect then the magnitude of rolling friction goes to zero.