A boomerang is a curved wood that when thrown comes back to the thrower as a result of asymmetrical lift; one of the underlying principles in aerodynamics. As Mason notes, there are several types of boomerangs; the curved boomerang, the cross stick boomerang, the boomabird, and the tumblestick (7)- all differing in length and the material used in making them and perhaps the purpose. Of the four types of boomerangs mentioned above, the curved boomerang is the most prevalent, and for this reason, it is the one is referred to in this paper. The boomerang was particularly popular with the aborigines of Australia. The aborigines are known to have been using the boomerang primarily for hunting purposes and sporting. In this light, the Aborigines had two types of boomerangs; the returning boomerang for sporting and the non-returning boomerang for hunting (Mason 7). To the aborigines, the boomerang was conventionally known as the “kylie” (Fisher 94). Others believed to have used the boomerang include the Egyptians, North Americans and the Hopi Indians, colloquially known as the Mosquis (Mason 8).
The Flight of a boomerang
When discussing the motion of a boomerang it is usually fascinating to examine the motion of a returning boomerang. Again, it is normal for a piece of any piece of wood to continue traveling in the same direction in which it was thrown until the force of gravity coupled with friction brings it to a halt on the ground. However, this is not the case with a boomerang. A piece of wood when compared to a boomerang differs in the sense that a piece of wood is simply one unit while a boomerang is composed of two units, which enables it (the boomerang) spin about a central point.
The returning boomerang does so due its shape and design of the two wings conjoined to form one unit. Designed as an aerofoil wing, the two wings experience different aerodynamic forces. With reference to a thrown boomerang, the boomerang moves forward while rotating at the same time (Fisher 98). This makes the upper wing have a higher aerodynamic force than the lower wing (Fisher 94). This can be better explained with reference to the air speed flowing over the surfaces of the wings; air flows faster over the surface of the upper wing than the lower wing; it can be said that the upper wing moves at a higher speed than the lower wing (Fisher 94). The lift, according to Bernoulli’s effect results from the fact that the speed of air on the upper part of the wing is greater than the speed of air on the lower side. Consequently, there results a pressure difference between the air pressure at the top and the air pressure at the bottom hence the boomerang is lifted.
The working of a boomerang
As mentioned earlier, the uneven forces on the wings of the boomerang, which result from the difference in air speeds over the upper and the lower surfaces of the two wings, cause the boomerang to tilt. Just like a bicycle, which makes a turn when the rider leans a bit, the boomerang turns as a result of the tilting through a process called gyroscopic precession; a process that obeys the gyro rule ( the gyro rule states that the spin axis chases the torque axis) (Fisher 99). The spin axis in this case refers to the axis about the boomerang rotates, and the torque axis is the line passing through the point at which the tilt is taking place. It is also worth noting that the direction taken by the boomerang is determined by the right-hand screw rule (Fisher 100).
Furthermore, the boomerang travels in a circle and circular motions always require a force that is directed towards the center of the circular orbit. For the boomerang, the force originates from the aerodynamic lift. The radius of the circular path followed by the boomerang is dependent on a number of variables; the density of the material used in making the boomerang, the cross-sectional area of the boomerang’s wings, the lift coefficient, width of the wings, and the density of air. As documented by Fisher (102), the radius of the path is determinable from Bod Reid’s equation below;
Canonically, with regards to the equation above, a boomerang made from a denser material and a large cross-sectional area of the winds coupled with a smaller wing width and aerodynamically effective wings (the determining component if the lift coefficient) will follow a larger circular path.
The discussion about the returning boomerang is never complete without a discussion of the improvisations that can be done to suppress the ability of the boomerang to return. As Fisher asserts, the major improvisation to eliminate the returning capability of the boomerang can be done to its wings (105). As seen earlier, the turning of a boomerang takes place because of titling. In this light, it is attestable that if the boomerang fails to tilt, then there are no chances that it will return. Therefore, if coins a tied closer to the tip of the wings, the boomerang will not be able to return (Fisher 105). Even though, Fishers explanation on how this can be achieved is not clear, one can clearly notice that placing the coins on the wing that experience a higher Bernoulli’s effect can limit tilting, thence rendering the boomerang non-returning.
Throwing a Boomerang
Concisely, a boomerang is a curved wood that returns to a thrower after a throw. The boomerang was particularly common with the Aborigines of Australia who used it for sporting and hunting. The flight and returning property of the boomerang is extensively dependent on the aerodynamic properties of the wing. Throwing a boomerang requires constant practice. In addition, the success of a boomerang throw depends on the shape, type, and material used in making the boomerang among other variables.
Fisher, Len. How to Dunk a Doughnut: The Science of Everyday Life. New York, NY: Arcade Publishing, Inc., 2002. Print.
Mason, Bernard S. Boomerangs; How To Make And Throw Them. Mineola, NY: Dover Publications, Inc., 1974. Print.