Effect of temperature on the dynamic properties of soccer balls

Soccer is played over a wide range of temperatures. Previous research has shown that the dynamic properties of sports balls, such as squash balls, tennis balls, and baseballs are dependent on temperature. The aim of this research was to determine whether the dynamic properties of soccer balls are temperature dependent. Quasi-static tensile testing was conducted on samples of soccer ball material, at nominal temperatures of 0, 20, and 40 °C. Normal impact testing at speeds up to 22 m/s was undertaken at nominal ball temperatures of 0, 20, and 40 °C. The stiffness of the material decreased as the temperature increased. The coefficient of restitution, contact time, and maximum deformation of the ball all increased with temperature. The mean coefficient of restitution was 0.82 ± 0.03 at 40 °C in comparison to 0.73 ± 0.02 at 0 °C. A foot-to-ball impact model combined with a trajectory model was used to simulate a penalty kick directed at the top corner of the goal. The results showed that the time available to the goalkeeper was 7 per cent shorter at 40 °C in comparison to that at 0 °C. Therefore, the time available for a goalkeeper to prevent a goal decreases as temperature increases.