ENERGY-DISSIPATION AND TRAPPING OF PARTICLES MOVING ON A ROUGH-SURFACE

We report on an experimental, numerical, and theoretical study of the motion of a ball on a rough inclined surface. The control parameters a re D, the diameter of the ball, theta, the inclination angle of the ro ugh surface, and E-ki, the initial kinetic energy. When the angle of i nclination is larger than some critical value, theta > theta(T), the b all moves at a constant average velocity, which is independent of the initial conditions. For an angle theta < theta(T), the balls are trapp ed after moving a certain distance. The dependence of the traveled dis tances on E-ki, D, and theta is analyzed. The existence of two kinds o f mechanisms of dissipation is thus brought to light. We find that for high initial velocities the friction force is constant. As the veloci ty decreases below a certain threshold the friction becomes viscous.