Gravity-Driven Motion of a Particle on an Inclined Plane with Controlled Roughness

We present an experimental and theoretical analysis of the motion of a single steel ball rolling on a rough inclined plane. This motion is well described by a Langevin equation with a viscous force. The constant of viscosity scales as ( R/r ) -3/2 , where R is the radius of the rolling ball and r a length scale describing the roughness of the surface. We find, furthermore, that the average distance L * the ball rolls on the plane inclined at an angle θ is r exp [ A(R/r) 3 sin 2 θ].