A ball weighing .2kg is traveling 20ms-1 to the left, a 20 000kg truck is traveling 25ms-1 to the right. What is the speed of the ball after the collision (M1V1) + (M2V2)before=(M1V1) + (M2V2)after This seemed so obvious, but i keep getting it wrong. The answer is 70ms-1. The only thing that i could be doing wrong is assuming the change in speed of the truck is negligible. Thanks for the help in advance.