In this paper, we have theoretically and experimentally studied a planar prism rolling on a fixed ramp in a small inclined angle.In order to deal with the problem of line impacts involved in the prisms motion,we propose a line-impact model that can properly reflect the dissipation and dispersion of energy occurring in the contact surface.Validation of the theoretical development is supported by the good agreements between our numerical and experimental results related to motions of many prisms made in distinct shapes and in different materials.