ABSTRACT
The direct free kick is an increasingly important component of the modern game, second only to the penalty in players’ and spectators’ expectations of a goal. This follows from a combination of the technology of the modern ball, and elite players’ ability to swerve it accurately when kicked with spin. There have been numerous theoretical and practical studies of the flight of a spinning ball (Tait, 1896; Mehta, 1985; Watts and Ferrer, 1987; Alaways and Hubbard, 2001; Bray and Kerwin, 2003). In Bray and Kerwin (2003), aerodynamic properties of a soccer ball (lift and drag coefficients) were obtained by comparing a mathematical model of the flight with experimentally determined trajectories. The results were used in conjunction with a model of the defensive wall to examine attackers’ and defenders’ options in this important ‘set play’.
