摘要：Nine soccer balls were tested for their friction against a leather sheet, using a force plate. An average normal force of 63.6 N was applied and the movement of the ball had an average velocity of 15 mm/s. Each test was repeated 15 times and the average Coefficient of Friction (COF) was reported. The following results were obtained: Jabulani (COF: 0.62 ± 0.05); Fracas (COF: 0.41 ± 0.01); Ordem 3 (COF: 0.63 ± 0.02); Teamgeist (COF: 0.38 ± 0.01); Brazuca (COF: 0.45 ± 0.01); Kopanya (COF: 0.39 ± 0.01); React (COF: 0.37 ± 0.01); Finale 15 (COF: 0.39 ± 0.06); Vintage T-panel leather ball (COF: 0.41 ± 0.02). Overall, the COF of all balls tested ranged between 0.37 and 0.62. The Finale 15 ball showed a decreasing COF trend with repeated trials and the React ball produced pronounced slip-stick phenomenon.
