Question

why is rolling friction less than kinetic friction as the only change is amount of area in contact but friction doesn't depend on surface area? (Ls-5,Laws of Motion,class XI)

Answer 1

let the velocity of centre of mass of the wheel be v.
then as the velocity at the top of the wheel is v + v = 2v
then as the velocity at the bottom of the wheel is v - v = 0
since the bottom point of the wheel is at rest the rolling friction is zero. This is for only when wheel is rolling on plane surface. In case of rolling on inclined plane rolling friction is not zero.
This is why the rolling friction is less than kinetic friction.