Problem: Train cars are coupled together by being bumped into one another. suppose two loaded train cars are moving toward one another, the first having a mass of 120,000 kg and a velocity of 0.300 m/s, and the second having a mass of 105,000 kg and a velocity of -0.120 m/s. (the minus indicates direction of motion.)
Part A: What is their final velocity?
Please give me an explanation for above problem.