Enter the Trebuchet

The above is an (old) drawing of a trebuchet. In position A, the arm is in its ready-to-throw position, with the throwing arm connected to a heavy weight on its short end, and to a sling containing its projectile on its long end. Position B shows the trebuchet in its swing after the arm is released, with the counterweight pulling down and swinging the long end of the arm up. This throws the sling up into the air, until it releases its projectile, which flies upward at an angle perpendicular to the angle of the arm at the release point.