A moving rail car collides with a stationary car that has identical mass, and the two cars begin to move together. If the momentum of the moving car was 450,000 kg•m/s, what is the total momentum of the two cars after the collision? A. 225,000 kg•m/s
B. 450,000 kg•m/s
C. 900,000 kg•m/s
D. Total momentum cannot be determined from this information.

Aheavy boy and a lightweight girl are balanced on a massless seesaw. the boy moves backward, increasing his distance from the pivot point. what happens to the seesaw? it is impossible to predict without knowing additional information. the side the boy is sitting on will tilt downward. the side the girl is sitting on will tilt downward. nothing; the seesaw will remain balanced.