The Physics of Boomerangs

The Physics of Boomerangs

The successful flight of a boomerang looks as though it never should happen. Its more or less circular flight path comes from the interaction of two physical phenomena: the aerodynamic lift of the arms of the boomerang and the spinning boomerang’s maintenance of angular momentum. Briefly put, the airfoil at the boomerang’s forward rotating edge provides more lift than its rearward rotating edge. This elevates one side of the boomerang. The spinning object maintains angular momentum by turning at a right angle to its axis of rotation. When the spin and the velocity of boomerang are just right, it flies away and returns in an aesthetically satisfying circle.

The boomerang’s distinctive flight starts with its aerodynamic properties. Boomerangs come in a variety of shapes. The traditional forms are variations on an L with equally long arms. There are also boomerangs with three or even four arms radiating from a center. And there are delta boomerangs.1 Whatever the configuration, every boomerang has airfoils at its extremities. Looking outward from the center of rotation of the boomerang, the left side of the blade is the leading edge of the air foil for right-handed throwers.2

As the boomerang spins, the airfoils at its perimeter create lift. Our text, Physics: A World View, discusses aerodynamics and Bernoulli’s principle. It explains the relationship between the velocity of a fluid and the pressure that the fluid exerts. A fluid gains energy when it speeds up as, for example when it goes through a constricting area in a pipe or passes around an airfoil. Since the gravitational potential energy is constant, the change is in kinetic energy. Since there is an acceleration of the fluid, the press...

... middle of paper ...

...d San Francisco. McGraw-Hill Company Limited, 1982. 20-21.

5http://www.grc.nasa.gov/WWW/K-12/airplane/bern.html. I also visited several Google sites, “boomerang,” though I did not draw on them for this project. They generally have a bit of (undocumented) history/anthropology, some physics, and throwing instructions. For example: http://www.gel-boomerang.com/, and http://www.boomerangs.org/ (pictures of some odd shapes).

This is consistent with my experience. Trying to put more spin on the boomerang mainly has the effect of making a throw unnatural and therefore prone to fly into the ground.

7When in college, my daughter would often suggest “going to throw a boomerang” as a first date. Her idea was that she learned a lot about a guy seeing him cope with failing miserably--a certainty the first time out with a boomerang--at a seemingly simple athletic activity.