Question

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?

Answer 1

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