Why Does a Boomerang Return?

(Lansing State Journal, May 21, 1997)

Question submitted by Ken Haley

Actually, Felix Hess, a Dutch physicist, wrote a book on why the boomerang returns. The way that a boomerang is thrown and the shape of the boomerang's arms are the two main reasons why a boomerang returns. Some boomerangs are shaped like bananas. The two arms of the banana-shaped boomerang are shaped just like airplane wings. The wings of the boomerang are flat on the bottom and curved on the top. Thus air moving over the top of the wings must move faster than the air moving underneath the wings, and the boomerang flies.

However, the wings of the boomerang are not identical. The rounded top of one of the "wings" points into the wind and the rounded top of the other "wing" points away from the wind. The boomerang is then thrown vertically so that it flies end over end through the air about ten times each second (so it is not thrown horizontally like a frisbee). So even though the boomerang is flying forward through the air, it is tugged backwards a small amount with each new revolution. As a result, pressure is created on top of the boomerang. The boomerang will gradually turn to the left as it traces a large circle and it will also "lie down" so that it travels back to the thrower spinning horizontally like a frisbee.

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