A 10. 0 g marble slides to the left with a velocity of magnitude 0. 400 m/s on the frictionless, horizontal surface of an icy new york sidewalk and has a head-on, elastic collision with a larger 30. 0 g marble sliding to the right with a velocity of magnitude 0. 200 m/s. Let +x be to the right. (since the collision is head-on, all the motion is along a line. ) (figure 1).