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Learning to throw a boomerang properly takes a lot of practice. And aerodynamics.
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Sources:
http://ullagunga.com/UllagungaSampleChapter.pdf
http://www.thenakedscientists.com/HTML/questions/question/1827/
http://hyperphysics.phy-astr.gsu.edu/hbase/brng.html#brng4
http://hyperphysics.phy-astr.gsu.edu/hbase/pber.html#airf
http://www.popsci.com/article/technology/what-makes-boomerang-come-back
(SciShow intro)

Hank: Humans have been using boomerangs for at least 20,000 years. The ancient polish used them to hunt animals, King Tut had a collection of them and of course they're an Australian icon.

There are also different kinds of boomerangs, and many of them, like the ones used for hunting, aren't meant to return. They just fly very precisely.

And even the boomerangs that are designed to come back to you are very hard to use, but if you do it right, you can use aerodynamics to get boomerang to land neatly in your hands.

It works because you're sending the boomerang spinning off at an angle, but you're also launching it forwards, so it end up with two speeds. A rotating speed and a forward speed.

When combined with the exact shape of the boomerang, the combination of those two types of speeds make it turn in a circle as it flies.

Boomerangs have two wings that connect at an angle and they're each shaped like an airplane's wings and what's know as an 'airfoil'. They have a rounder, blunter edge, called a leading edge and a sharp tapered edge, called a trailing edge. And the bottom of the wing is flat, while the top is beveled.

When air strikes an airfoil, it goes over the leading edge and pushes downwards off the trailing edge, creating a downward force of air. Since every action has an equal and opposite reaction, this downward force of air off the wing, pushes that wing in the opposite direction, generating lift.

And the faster an airfoil moves through the air, the more lift it gets. Boomerangs only work when they're thrown at an angle with your arm around 20º away from the top of your head. You flick your wrist so it spins through the air like a propeller.

So one wing will be at the top of each spin and the other will be at the bottom. When one wing reaches the top of the spin, it's both moving forward and rotating forward. And that means its going faster and generating more lift than the bottom wing which is rotating in the opposite direction of the forward movement.

This unbalancing of forces called 'torque', causes the boomerang to tilt and follow a curved path. The circles could be very large or very tight, depending on how fast the boomerang is traveling and at what angle.

Which is why, even if you send it spinning through the air, it takes some skill to get that boomerang to land softly in your hands and not over the fence in your neighbors yard.

This question was asked by our Patreon patron Jordan Francisco, so thank you for the question, and thank you to all of our Patreon patrons who keep these answers coming.

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(SciShow outro)