The question is: - Two billiard balls of equal mass move at right angles and meet at the origin of an xy coordinate system. Ball A is moving upwards along the y axis at 2.0 m/s, and ball B is moving to the right along the x axis with speed 3.7m/s. After the collision, assume elastic, ball B is moving along the positive y axis. What is the final direction of ball A and what are their two speeds? How would I do this one and what formulas would I use??