A 1.0-kg mass is attached to a string wrapped around a shaft of negligible mass and having a 8.0-cm radius. A dumbbell-shaped "flywheel" made from two 0.500-kg masses is attached to one end of the shaft and perpendicular to its axis. The mass is released from rest and allowed to fall 0.7 m to the floor. It reaches a speed of 1.2175 m/s just before the striking the floor. How far apart are the masses of the dumbbell?