Halliday, Resnick & Walker — Rolling, Torque, and Angular Momentum: Problem 81

Change in angular momentum. In Fig. 11.8.6, a Texas cockroach with mass \(m = 0.0500 \text{ kg}\) (they are large) rides on a uniform disk of mass \(M = 10.0m\) and radius \(R = 0.100 \text{ m}\). The disk rotates like a merry-go-round around its central axis. Initially, the cockroach is at radius \(r = R\) and the angular speed of the disk is \(\omega_i = 0.800 \text{ rad/s}\). Treat the cockroach as a particle. The cockroach crawls inward to \(r = 0.500R\). What is the change in angular momentum of (a) the cockroach–disk system, (b) the cockroach, and (c) the disk?