Momentium and conservation of energy

Question

There are three box cars connected together moving at a steady 24.0m/s. They hit a fourth box car that is at rest and stick together. Find the speed of the four cars and how much kinetic is dissipated in the collision.

Answer 1

(a) The speed of the four cars after the collision is:

(b) The kinetic energy dissipated in the collision is:

The speed of the four cars after the collision is 18.0 m/s, and the kinetic energy dissipated in the collision is 273.6 m²/s².