Question

a. How much work is done by the motor in a CD player to make a CD spin, starting from rest? The CD has a diameter of 12.0 cm and a mass of 15.8 g. The laser scans at a constant tangential velocity of 1.20 m/s. Assume that the music is first detected at a radius of 38.0 mm from the center of the disk. Ignore the small circular hole at the CD’s center.

b. A trap door, of length and width 1.70 m, is held open at an angle of 65.0° with respect to the floor. A rope is attached to the raised edge of the door and fastened to the wall behind the door in such a position that the rope pulls perpendicularly to the trap door. If the mass of the trap door is 19.4 kg, what is the torque exerted on the trap door about the hinge by the rope? Enter a positive value if the torque is in counterclockwise direction and enter a negative value if the torque is in clockwise direction.

Answer 1