HELP NEEDED!!!!!!

Question

In an isolated system, two cars, each with a mass of 2,000 kg, collide. Car 1 is initially at rest, while Car 2 was moving at 20 m/s. What is their combined momentum after the collision?
A. 0 kg-m/s
B. 40,000 kg-m/s
C. 20,000 kg-m/s
D. 20 kg-m/s

Answer 1

momentum is the product of mass and velocity.

In a colission, momentum is conserved.  

Since Car 1 was at rest , its initial momentum was 0.

The momentum of C was 2,000 kg x 2o m/s

= 40,000 kgm/s.