Question

in rotation what is different between rolling friction and kinetic friction

and why rigid body why we don't use rolling friction although they are rotating

Answer 1

rolling friction is friction between a point and surface which change its position every second ie displacement of same point is zero under same friction hence here workdone by friction is zero. Where as under kinatic friction there is a motion of same point under same friction force and hence in this situation there is a net displacement and hence work by this force.

iin rigid bodies we dont use rolling friction as net work done is zero hence there is no effect on energy loss. It just favor the motion without any loss hence is not taken into account for any calculation purpose or force diagram