Sometimes friction is most desirable. We cannot write if there would be no friction between paper and pencil. Friction enables us to walk on the ground. We cannot run on slippery ground.

            A slippery ground offers very little friction. Hence, anybody who tries to run on the slippery ground may meet an accident. Similarly, it is dangerous to apply brakes with full force to stop a fast-moving vehicle on a slippery road.

           Birds could not fly if there is no air resistance. The reaction of pushed air enables birds to fly. Thus, in many situations, we need friction while in other situations we need to reduce it as much as possible.