Problem 8-34 Elastic collision - C

A superball of mass \(22\; g\) rolls with a speed of \(3.5\; m/s\) toward another (stationary) superball of mass \(27\; g\). If the balls have a head-on elastic collision, what are the velocities magnitudes and directions) of the balls after the collision?
[Ans. \(3.1\; m/s\) forward and \(0.4\; m/s\) backward]

No. Or perhaps yes. In this case you are guessing that \(v{_2}'\) is negative. It may be but you will have to remember that you have made it negative as you continue. It is better to choose all unknown velocities positive and any that are negative will come out with a minus sign in the solution. So the best choice is (B).