A uniform sphere of radius r and mass m is placed with no initial velocity on a belt that...

A uniform sphere of radius r and mass m is placed with no initial velocity on a belt that moves to the right with a constant velocity v1 Denoting by µk the coefficient of kinetic friction between the sphere and the belt, determine (a) the time t1 at which the sphere will start rolling without sliding, (b) the linear and angular velocities of the sphere at time t1.