Question

A railroad car of mass m is moving with speed u when it collides with and connects to a second railroad car of mass 3m, initially at rest, as shown above. How do the speed and kinetic energy of the connected cars compare to those of the single car of mass m before the collision?

Answer 1

Take a look at the picture. The speed of the connected cars is 1/4 of the single car’s speed, and the kinetic energy is 1/4 of the single car’s kinetic energy