In the rotating assembly shown, arm OA and the attached motor housing B together weigh 1...

In the rotating assembly shown, arm OA and the attached motor housing B together weigh 10 lb and have a radius of gyration about the z-axis of 7 in. The motor armature and attached 5-in.- radius disk have a combined weight of 15 lb and a radius of gyration of 4 in. about their own axis. The entire assembly is free to rotate about the z-axis. If the motor is turned on with OA initially at rest, determine the angular speed N of OA when the motor has reached a speed of 300 rev /min relative to arm OA.