boomerang

How to make boomerangs that come back
Introduction Boomerangs are amazing! What seems to be a simple curved bit of wood can be thrown away from you and then come right back and land in your hand. Boomerangs use many laws of physics in their motion including inertia, Bernoulli's effect, gyroscopic precession, gyroscopic stability and Newton's laws of motion. They are sensitive to their size, shape and aerodynamic profile, as well as wind and rising thermals.
However, it is not very difficult to make a quality boomerang that can be thrown in such a way that it will be catchable almost every time. You don't need to know about physics. You don't even need to know how changes in the boomerang produce different flight patterns. Just so long as you can tell if a boomerang is not coming back, you can tune the boomerang so that it does.