title: Rolling friction on a granular medium.
abstract: We present experimental results for the rolling of spheres on a granular bed. We use two sets of glass and steel spheres with varying diameters and a high-speed camera to follow the motion of the spheres. Despite the complex phenomena occurring during the rolling, the results show a friction coefficient nearly independent of the velocity (0.45-0.5 for glass and 0.6-0.65 for steel). It is found that for a given sphere density, the large spheres reach a longer distance, a result that may also help explain the rock sorting along natural stone accumulations at the foot of mountain slopes.
authors.affiliation: Department of Geosciences, University of Oslo, P.O. Box 1047 Blindern, 0316 Oslo, Norway.
authors.forename: Fabio Vittorio
authors.initials: FV
authors.lastname: De Blasio
authors.forename: May-Britt
authors.initials: MB
authors.lastname: Saeter