An atlatl or spearthrower is perhaps humanity’s oldest technology for accelerating projectiles. The dynamics prior to launch of the dart projectile have been much discussed in the literature. In this article we present a simple new model of launch dynamics and show that dart flex is not an important factor in determining launch speed, but it increases accuracy. The atlatl is a lever but only indirectly; the significant parameters for increasing launch speed are applied energy, and angular difference between force direction and dart direction. This study exhibits some instructive elements of Newtonian mechanics.
References
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This Nahuatl word is usually pronounced aht-LAT-l in English, though the Nahuatl speakers of Mexico would drop the final l.
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See, for example, the YouTube videos “Atlatl competition in Fond du Lac, WI,” “What is an atlatl?” and “Primitive Technology: Spear Thrower.” To see how to make an atlatl, see the YouTube videos “Making an Atlatl Part I,” “Making an Atlatl Part II,” or “How to Make a Very Simple Homemade ATLATL.”
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Small angle so that not much energy is wasted. Also, as we will see, the flexing of darts helps with accuracy when the angle ε is small.
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See, for example, the YouTube video “Valley of Fire atlatl event 2014,” which shows slow-motion footage of atlatl launches confirming two of the assumptions made in this paper: that the direction of the applied force is approximately constant and that the dart flexes (but only with a small amplitude) during the launch phase.
14.
The Wikipedia site “Euler’s critical load” is clear and comprehensive concerning the maximum load that can be borne by a column.
15.
That is to say, the energy of motion of the dart center of mass is much greater than the vibration energy (the motion of the dart about the center of mass).
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).© 2019 American Association of Physics Teachers.
2019
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