The 0.5-lb ball is guided along the vertical circular path r = 2rc cos θ using the arm OA....

The 0.5-lb ball is guided along the vertical circular path r = 2rc cos θ using the arm OA. If the arm has an angular velocity   and an angular acceleration   at the instant θ = 30°, determine the force of the arm on the ball. Neglect friction and the size of the ball. Set rc = 0.4ft.