A person stands on the roof of a building, 40 m high. He throws a rock directly up at 10 m/s. How long until it hits the ground? I know how to do this in 2 steps: compute height that the rock rises to (~5 meters), then compute time for an object to free fall from 0 m/s to the ground ~45 meters below. But isn't there a way to do it in one step?