NEET Class neet Answered

For rolling friction one need to understand the concept of toppling throughly. In case of static or kinetic friction, the forces which are responsible for providing friction is horizontal whereas in case of toppling the block the force which opposes toppling is the normal reaction of the block which resists the horizontal force which is trying to topple the block. So by narrowing the base we are decreasing the torque because torque is the product of force and displacement. Hence when we narrow  the base n(n is very large) number of times the sides od the block increses as a result its surface area decreases and finally it becomes circle and hence the resistive torques becomes very small.