Question

A ball is dropped from rest from the top of a building and strikes the ground with speed v sub f. From ground level, a second ball is thrown straight upward at the same instant that the first ball is dropped. The initial speed of the second ball is v sub o equals v sub f, the same speed at which the ball will eventually strike the ground. Ignoring air resistance, decide whether the balls cross paths at half the height of the building, above the halfway point, or below the halfway point. Give reasoning.