Air moves faster over the top of an air plane wing than along the bottom of the wing because
of the airfoil shape. The Bernoulli effect
tells us this results in higher air pressure along the bottom flat surface than along its
curved surface. It is this difference in air pressure that produces aerodynamic lift.
As the boomerang spins through the air, the opposing tilts of the wing segments produce
lift in the same direction. The joined wings travel in opposite directions through the air.
This arrangement is like a helicopter rotor. At its heart, a boomerang is just a rotor
that isn't attached to anything.
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The leading edges of the two wings face in the
same direction, like the blades of a helicopter rotor.
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Turning our attention to the diagram above, we see that
the two wings are arranged so that the leading edges face in the same rotational direction.
Combining this information with the lift priciple, it is reasonable to assume that a
boomerang would simply fly off in one direction as it spun.
If you held it horizontally when you threw it, like you do with a Frisbee (a flying disc toy),
the motion arising from lift should be upward. The boomerang would fly up into
the sky like a helicopter taking off, until it stopped spinning and gravity pulled it down
again.
And, if you threw it end over end, which is the proper way to throw a boomerang,
it seems that it should simply fly off to the right or left. Why doesn't this happen?
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