A railroad car of mass 2.50 * 10^4 kg is moving with a speedof 4.00 m/s. It collides and couples with three other railroadcars, each of the same mass as the single car and moving in thesame direction with an initial speed of 2.00 m/s.
A. what is the speed of four cars immediately after the collision?
B. how much energy is transformed into internal energy in thecollision?