Playing pool, you send the cue ball head-on (that is, along the line joining the centers of the two balls) into the stationary 8 ball, and the cue ball stops as a result of the collision.

(a) Describe the momentum of each ball before and after the collision.

(b) Show that your answer to part \(a\) is consistent with Eq. \(4.18, \Delta \vec{p}=\vec{j}\). (Assume that pool balls have identical inertias.)