A ball that rolls on parallel tracks, whose width is less than the diameter of the ball, experiences both translational and rotational motions. The linear accelerations of the ball for cases of rolling and slipping are derived theoretically, and these accelerations have also been determined by performing experiments when the width and the angular elevation of the tracks are controlled. Data show when slipping occurs for the rolling motion, and the onset of slipping is used to compute the coefficient of kinetic friction for a sphere. A second method of determining the coefficient of friction, for the sphere slipping without rolling, provides confirmation for this analysis.