A railroad car having mass M moving at a speed v1 collides and couples with two coupled railroad cars, each of the similar mass M and moving in the similar direction at a speed v2.
(i) Determine the speed vf of the three coupled cars after the collision in terms of v1 and v2?
(ii) Determine how much kinetic energy is lost in the collision? Answer must be in terms of M, v1, and v2.