  We report an experimental, numerical and theoretical study of the motion of a
ball on a rough inclined surface. The control parameters are $D$, the diameter
of the ball, $\theta$, the inclination angle of the rough surface and $E_{ki}$,
the initial kinetic energy. When the angle of inclination is larger than some
critical value, $\theta>\theta_{T}$, the ball moves at a constant average
velocity which is independent of the initial conditions. For an angle $\theta <
\theta_{T}$, the balls are trapped after moving a certain distance. The
dependence of the travelled distances on $E_{ki}$, $D$ and $\theta$. is
analysed. The existence of two kinds of mechanisms of dissipation is thus
brought to light. We find that for high initial velocities the friction force
is constant. As the velocity decreases below a certain threshold the friction
becomes viscous.
