How a boomerang comes back

How a boomerang comes back

Aerodynamic throwsticks were developed by Stone Age civilizations in different parts of the world as long as 15,000 years ago. The Australian aborigines are the best known; however, these special hunting weapons were also developed in other areas including ancient Egypt, the American Southwest, and eastern Europe. While there are many stories of how the returning boomerang came to be (many rooted in myth and misinterpretation), most anthropologists agree that it originated from the throwstick. The throwstick, called a kylie by the native Australians and a rabbit stick by the Hopi Indian people of pre European America, was a heavy, non-returning aerodynamic weapon thrown horizontally to kill or stun prey. At some point (perhaps by accident) the stick became more  curved and refined (and much lighter) so that, when thrown vertically, it would return to the thrower. These true boomerangs were probably only used for fun and games, not as weapons. Today’s modern boomerangs are sports equipment and should be treated with the same respect as a baseball. Baseballs and boomerangs both can be dangerous when used carelessly. When used properly, they are safe and fun.

A boomerang is basically a single-winged aircraft propelled through the air by hand. Boomerangs have two 'wings’ joined in a V-shape. Both wings have an airfoil-shaped cross-section just like an aircraft wing. An airfoil is flat on one side but curved on the other with one edge thicker than the other  this helps the boomerang stay in the air due to lift.

Lift is generated as the air flowing up over the curved side of the wing has further to travel than the air flowing past the flat side. The air moving over the curved surface must therefore travel quicker in order to reach the other edge of the wing.Because the two sides of a boomerang have different air speeds flowing over them, as it spins the aerodynamic forces acting upon it are uneven. This causes the section of the boomerang moving in the same direction as the direction of forward motion to move faster through the air than the section moving in the opposite direction. These uneven forces make the boomerang start to turn in and follow a circular route, eventually heading back to the thrower.
Conclusion
1. The arms of a boomerang have an airfoil design that produces lift.
2. Unevenness in the distribution of the lift generates a torque. Together with precession it makes the boomerang fly in a circle.
3.. The banana shape generates another torque that, again through precession, turns the boomerang into a horizontal position.