1. The problem statement, all variables and given/known data A 1500-kg car is traveling north at 25 m/s when it strikes a 2000-kg car traveling east at 20 m/s. The cars stick together after the collision. What is the final velocity of the two cars? 2. Relevant equations m1v1 + m2v2 = (m1 + m2)vf 3. The attempt at a solution 1500(25) + 2000(20) = (1500 + 2000)vf vf = 22.14 m/s The answer was incorrect. I then thought vectors would be needed but wasn't sure. Can someone guide me through this problem?