Physics behind Boomerangs

Figure 1: Picture of a Boomerang

Boomerangs are tools used by Aboriginal Australians in hunting and warfare. Boomerangs are also works of art, with different paintings relating to different traditions and legends. The famous trait of the boomerang is that it can return to the thrower without the thrower having to move! 

Shape of the Boomerang: 

Figure 1: Shape of a boomerang

The shape design of a boomerang resembles an aerofoil which is similar to an airplane’s wing. The aerofoil shape in A and B (Ref. Figure 1) allows the boomerang to generate lift as it moves through the air. When thrown, the upper arm of the boomerang travels faster than the lower arm due to its forward motion combined with its spin. This speed difference creates a pressure differential: the air pressure on top of the upper arm is lower than that underneath, resulting in a net upward lift force on the upper arm and a downward force on the lower arm to generate lift. 

Due to its non-uniform shape, the upper arm of the boomerang generates more lift to allow the boomerang to gain torque. The gain in torque causes the boomerang to tilt and change direction during flight to create a circular-like motion. 

Angular Momentum and Precision: 

Figure 2: Spinning Orientation

When thrown, the boomerang spins from the center of mass (Ref. Figure 3). The spinning motion gives rise to Gyroscopic precession where spinning objects move in resonance to an applied torque with the equation =Jddt. Therefore, the uneven lift of the torque prevents the boomerang from tipping and falling flat.  

It is seen that as lift increases and creates torque, it can also dictate the angular velocity and direction of flight. 

Flight Path 

Figure 4: Flight path

The combination of lift and Gyroscopic Precession allows the boomerang to travel in a circular flight path. Think of it being similar to the moon and the Earth where the moon spins around a circular path. However, the boomerang’s trajectory is not perfectly circular due to unbalanced aerodynamic forces, making it more of an ellipse (Ref. Figure 4). 

The radius of the flight path can also be derived from the mass, moment of inertia, and its aerodynamic properties. From the equation R=4JCLa4, it is seen that the boomerang’s flight path is not dictated by the throwing technique. Rather, it is dictated by the physical properties of the boomerang, which a is directly a characteristic of the boomerang. 

Impact and Fun Fact: 

Boomerangs are a symbol of aboriginal culture in Australia. Not only is it helpful in hunting scenarios, but it is also useful in signaling and combat. In modern days, tourists visiting Australia can try throwing a boomerang. 

Works Cited: 

Hull, L. (2019). A look at the physics behind a boomerang’s ability to fly and return. [online] Distilled Thoughts. Available at: https://distilledthoughts.home.blog/2019/09/15/a-look-at-the-physics-behind-a-boomerangs-ability-to-fly-and-return/.

Hunt, H. and Cambridge (2001). Boomerang Theory. [online] Available at: https://www3.eng.cam.ac.uk/~hemh1/boomerang_theory.pdf [Accessed 5 Nov. 2024].

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Tikkanen, A. (2024). Boomerang | weaponry. [online] Encyclopedia Britannica. Available at: https://www.britannica.com/technology/boomerang-weaponry.

Wooden Boomerangs for Sale. (2017). Boomerang ‘Kangaroos’. [online] Available at: https://woodenboomerangs.com/product/boomerang-kangaroo-australischer-bumerang-der-aborigines-traditionelle-bumerangs-australian-boomerang/.

www.rangsboomerangs.com. (2022). Boomerang Info - how it works | Rangs Boomerangs. [online] Available at: https://www.rangsboomerangs.com/info-how-it-works.