Let A represent the ball moving at 2.00 m/s, and call that direction the positive direction. Let B represent the ball moving at 3.60 m/s in the opposite direction. Thus, VA =2.00 m/s and VB=-3.60 m/s. Use Eq. 7-7 to obtain a relationship between the velocities.

VA-VB=-(V’A-V’B) → V’B = 5.60 m/s+ V’A

Substitute this relationship into the momentum conservation equation for the collision, noting that MA=MB