Multiple-Concept Example 7 outlines the general approach to problems like this one. Concept Simulation 7.2 provides a view of this elastic collision. Two identical balls are traveling toward each other with velocities of -4.2 m/s (ball A) and +8.3 m/s (ball B), and they experience an elastic head-on collision. Obtain the velocities (magnitude and direction) of (a) ball A and (b) ball B after the collision.