Two hockey players are skating toward each other on a frictionless ice. One is moving at 1 m/s while the other is traveling at 2 m/s. The players collide and stick together. Find their combined speed.

Determine the moment of the force f about an axis extending between a and c. express the result as a cartesian vector. a is at the origin, c is at (4,3,0) and f = (4i + 12j -3k) lb coming out of b (4,3,-2).