A train car with mass m1 = 515 kg is moving to the right with a speed of v1 = 7.5 m/s and collides with a second train car. The two cars latch together during the collision and then move off to the right at vf = 4.8 m/s.Now the same two cars are involved in a second collision. The first car is again moving to the right with a speed of v1 = 7.5 m/s and collides with the second train car that is now moving to the left with a velocity v2 = -6 m/s before the collision. The two cars latch together at impact.What is the final velocity of the two-car system? (A positive velocity means the two train cars move to the right – a negative velocity means the two train cars move to the left.)