You are riding in a bumper car. You and your bumper car have a combined mass of 370 kg and are moving at a rate of 2 m/s when you crash into a stalled bumper car that holds your mom and dad and has a combined mass of 470 kg. After the collision your bumper car stops, what is the speed of your parents' bumper car after the collision?

This is based on the conservation of momentum - The total momentum in a closed system remains constant unless an external force acts upon it.

We know the momentum of your bumper car before the collision is 370x2=740 kgm/s. Since your car stops after the collision, all of the momentum must be transferred to the other car.

So we can substitute in the known values:

p=mv

740 = 470*v

v=740/470 = 1.57m/s to 3sf