Question

A railroad car with a mass of 1.91 multiplied by 104 kg moving at 2.86 m/s 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 1.40 m/s.

What is the speed of the three joined cars after the collision?

What is the decrease in kinetic energy during the collision?

Answer 1

conservation of momentum applies

Momentum before= momentum after
M*2.86+2M*1.40=3M*V
find V

Answer 2

How do you find the "decrease in kinetic energy during the collision?"