Question

Complete the 2 questions below. Question 1 Axle A disk is attached to an axle, about which it can freely rotate without friction. The axle is parallel to the floor, and the disk has a mass of 4.30 kg and a diameter of 25.6 cm. The disk is held so that its centre of mass is as high as the axle, and then released from rest. What is the angular velocity of the disk when it is directly below the axle? Question 2 You're feeling particularly lazy and decide to open a door by firing a bullet at it. The door has a mass of 9.10 kg and is 1.60 m wide, and the 10 g bullet, traveling at 365 m/s, hits the door at the edge opposite the hinges. The bullet stops inside the door, which then swings open. What is the angular velocity of the door just after the bullet hits it? Click "Submit Answer" below to submit both of your answers. Submit Answer Tries 0/10

please explain the question's in-depth. Severely confused

Answer 1

Radius, r = 0.256/2 = 0.128 m

Moment of inertia, I = mr^2 + 0.5 mr^2 = 1.5 mr^2

Using work energy theorem,

Work done = change in kinetic energy

mgr = 0.5 I w^2

m x 9.8 x 0.128 = 0.5 x 1.5 x m x 0.128^2 x w^2

Angular velocity, w = 10.10 rad/sec

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