Kevin has a mass of 78.5 kg and is skating with in-line skates.
He sees his 22.50 kg younger brother up ahead standing on the sidewalk,
with his back turned.
Coming up from behind, he grabs his brother and rolls off at a speed of 1.95 m/s.
Ignoring friction, find Kevin's speed just before he grabbed his brother.
i'm not sure if this is for collisions in one or two dimensions, or both?