In a recent episode of Mythbusters, Brian and Jon (the new MythBusters) wanted to see what happens when you shoot an arrow straight up into the air. It will obviously come back down—but would it still be moving fast enough to kill you? If you are a MythBuster, the best option is to actually shoot an arrow straight up into the air and measure its velocity on impact. But for normal people, it might be better to just calculate the final arrow speed.