Two discs A and B are mounted coaxially on a vertical axle. The discs have moments of inertia I and 2I respectively about the common axis. Disc A is imparted an initial angular velocity 2 using the e potential energy of a spring compressed by a distance x1. Disc B is imparted an angular velocity by a spring having the same spring constant and compressed by a distance x2. Both the discs rotate in the clockwise direction. The ratio of x_1/x