A compact disc (CD) spins at a constant angular speed while it is being read
PHYSICS · Single correct · AP · Physics C: Mechanics · Torque and Rotational Dynamics · Torque and Rotational Dynamics
Problem
A compact disc (CD) spins at a constant angular speed while it is being read. Which of the following best explains why a point on the outer edge of the disc moves faster than a point located halfway between the center and the edge?
(a) Because the centripetal force Fc=rmv2 is larger at the rim, this larger force drives the outer edge to move faster.
(b) The outer edge completes more revolutions per unit time than points closer to the center, so its speed is greater.
(c) Points on the outer edge have a larger radius, so their linear speed v=ωr is larger even though every point shares the same angular speed.
(d) Extra mass near the rim must move faster to conserve angular momentum, so the edge speeds up relative to the center.