Spinning Soccer Ball Trajectory

Abstract

As can be remembered from the recent World Cup, uncertainties in the trajectory of a soccer ball at high speeds have led to some criticism on the ball manufacturers. The existing ball trajectory models assume that as the ball spins, a layer of air, say a boundary layer, follows the motion of the ball, thus spins with it. This, in turn, induces a velocity difference on the sides normal to ball's trajectory. The velocity difference then leads to pressure difference due to Bernoulli's principle. If ω represents the axis of spin and