A railroad car with a mass of 2.46 x 10^4 kg moving at 3.25 m/s collides and joins with two railroad cars already joined together, each with the same mass as the single car and initially moving in the same direction at 1.49 m/s.
A) What is the final speed of the three joined cars after the collision?
B) What is the decrease in kinetic energy during the collision?