Аннотация:The motion of a two-body system along a straight line on an inclined (in particular, horizontal) plane is considered. Anisotropic dry friction is assumed to act between each of the body and the plane of motion. The motion of the system is excited by changing periodically the distance between the bodies. Necessary and sufficient conditions for the motion of the system upward along the inclined plane or along a horizontal plane are obtained for the case where the force of friction is small in comparison with the excitation force.