Rolling as a frictional equilibration of translation and rotation

In this paper we discuss the role of static and kinetic friction in the dynamics of rolling motion. First, the role of kinetic friction in bringing about and maintaining an equilibration, called free rolling, between the translational and rotational motions of a rigid disc on a rigid surface is briefly discussed. We then extend the discussion to real wheels and provide a physical origin of rolling friction by introducing a new concept, quasi-rolling, to explain how pure rolling can exist even in the presence of some sliding. Our treatment is specifically applicable to rolling motion between two hard surfaces, such as ball- and roller-bearings.