Collision dynamics of soccer balls

The purpose of this study was to present energy dissipation during the collision (EDDC) by determining the collision dynamics. The soccer balls' that have different brands were kicked nine times toward unbreakable tempered glass (TG) (1x1x0.007m) in three inner pressures (0.6, 0.8, 1.0 bar). The two high-speed cameras (SA3 120K, Japan) were used to determine collision dynamics and ball imprint area on TG. The cameras synchronized and were set to record 6000 Hz in a second and 1/10000 shutter speed. All collision were processed to determine indentation amount (IA), contact surface area (CSA), force and energy dissipiation (ED) by using Python programming language, and a new methodological approach was developed for determine EDDC. The accuracy control for CSA, IA and, force results were made. EDDC was calculated after determining the truth of the obtained data. The accuracy of the results by taking average of the EDDC results (MED) was compared with the formula that was placed in the literature. The force results were analysed by Spearman's rank correlation. The CSA, model-experiment IA, and force results were analysed by root mean square error and Spearman's rank correlation. The Student-T Test was used for accuracy determination of EDDC results. The differences among the ball brands to the ED and IA were examined with one-way ANOVA test. Tukey test was used to determine for difference between groups, It was found that the MED was statistically significant different in 1.0 bar inner pressure according to ball brand (F=3.246, p<0.05). In addition, the IA was statistically significant different in 1.0 bar inner pressure (F=4.838, p<0.05). IA and EDDC showed significant differences according to the brands. EDDC, depending on the ball quality, decreased at higher inner pressure values regardless of the brand. Consequently, the present study exhibited that ball quality becomes a critical factor in collision dynamics at high inner pressure values, considering that ball inner pressure may vary between 0.6 and 1.0 bar in official soccer matches. Keywords: Soccer, collision dynamics, impact, coefficient of restitution, ball quality, energy dissipation