The problem of a disc or cylinder initially rolling with slipping on a surface and subsequently transitioning to rolling without slipping is often cited in textbooks. Students struggle to qualitatively understand the difference between kinetic and static frictional forces--i.e., whereas the magnitude of the former is known, that of the latter can only be described in terms of an inequality while the relative velocity at the point(s) of contact is equal to zero. In addition, students have difficulty understanding that frictional forces can act in the direction of motion--i.e., they can accelerate objects. [Translated from the Spanish by Eduardo Speranza.]