A car traveling 20 m/s to the north collides with a car traveling 10 m/s to the

south. Each car has a mass of 800 kg. If the system is defined as the two

cars, what is the change in momentum of the system due to the collision?

A. 24,000 kg. m/s

B. 16,000 kg•m/s

C. 0 kg•m/s

D. 8000 kg•m/s

Answer: C

Explanation:

In collision, whether elastic or inelastic collisions, momentum is always conserved. That is, the momentum before collision will be equal to the momentum after collision.

Change in momentum of the system will be momentum after collision minus total momentum before collision.

Since momentum is a vector quantity, the direction will also be considered.

Momentum = MV - mU

Let

M = 800 kg is going north

at V = 20 m/s and the other car

m = 800 kg is going south

at U = 10m/s.

Substitute all the parameters into the formula

Momentum = (800 * 20) - (800 * 10)

= 8000 kgm/s

The final momentum after collision will also be equal to 8000 kgm/s

Change in momentum = 8000 - 8000

Change in momentum = 0