A pendulum consists of a massless rod of length L = 60 cm attached to the center of a circular disk of mass m = 2 kg. The top of the rod is hinged at the top to the ceiling. The moment of inertia of the pendulum is 0.77 kg-mz. At one instant in time the rod makes an angle of 20 to the vertical, as shown at right. 1 What is the radius of the disk? side View looking north 2 What is the angular acceleration of the pendulum at the instant shown