ИСТИНА

The possibility of a two-body system to move upward along an inclined line is investigated. The system is controlled by the force of interaction of the bodies so that the distance between the bodies and their velocities are periodic functions of time. The friction between the bodies and the line is Coulomb’s dry friction. Necessary and sufficient conditions for the possibility of periodic upward motion of the system are proved. The motion is possible if and only if the smaller body can start moving upward the line from a state of rest while the bigger body is at rest. An algorithm of the upward motion is presented.