Wednesday, December 7, 2011

Physics of Javelin


Javelin throwing has been a sport since the beginning of the Greek Olympics and spear throwing has been part of human societies for much much longer (400,000 years according to Wikipedia). Many factors factor into the flight of the javelin: the running speed of the thrower upon release, the torque generated by the thrower when twisting, the angle of release, wind speed and direction, aerodynamic lift and drag, air resistance, gravity, the type of javelin itself and many others. Because gravity is consistently acting on the javelin after release the thrower must do his or her best to maximize distance by trying to optimize the horizontal vector of their force with the vertical component of their throw to maximize distance.
            Men’s javelins measure about 8.5 feet and 800 grams while those of women measure about 7.25 feet and 600 grams. In 1986 for men and 1999 for women the center of mass of the javelin was moved forwards about 4cm so that it would be further away from the centre of pressure (the point at which the aerodynamic forces of lift and drag act) which brings the javelin nose down earlier in flight, shortening the distance thrown. This also changed the optimum throwing angle from approximately 30°-32° to approximately 40°, causing more lift in the throw. In summation I hope that I’ve made it clear that there is much more physics to the art of javelin throwing than meets the eye. - Post written by Mike Reitano


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