Researchers investigate spin of World Cup football

The spin of the football used in the 2006 World Cup, has been newly analysed by a University of Sheffield academic, providing valuable information for professional sports engineers and scientists as well as football designers and manufacturers. Dr Matt Carré from the University´s Department of Mechanical Engineering, along with Associate Professor of Physics, John Eric Goff from Lynchburg College, Virginia, performed experiments in which the Adidas Teamgeist ball was launched from a machine while two high-speed cameras recorded portions of the trajectory (the flight path of the ball). When in flight, spinning balls typically experience a force perpendicular to the plan of spin (for example, causing a ball with top spin to dip). Using the trajectory data and published drag coefficients, Professor Goff and Dr Carré extracted the aerodynamic coefficients linked to this perpendicular force for a wide range of spin parameters, including several spin parameters that have not been obtained by today´s wind tunnels. Here, the "spin parameter" refers to the amount of spin relative to ball speed, so high spin parameters are achieved by having a low-speed ball with a large amount of spin. Flight behaviour of balls with different orientations, launch speeds and spins were examined by the researchers and the results compared with existing data from wind tunnel studies. The findings, published in the European Journal of Physics , show that the coefficients related to the amount of perpendicular force begin to level off at high spin parameters.