Effect of Rosin Powder on Friction between Finger and Baseball Ball

Abstract

Rosin powder, which consists mainly of magnesium carbonate powder and pine rosin, has been used empirically as an anti-slip agent in baseball pitching. However, it is unclear whether the rosin powder increases friction between baseball ball and a finger. In this study, the effect of rosin powder on the frictional characteristic between baseball ball and a finger was investigated by sliding friction test using a force plate. A leather sheet of baseball ball was adhered to the force plate. Ten young adult male participated and they were asked to slide their right index finger on the leather sheet of baseball ball under various normal load and sliding velocity conditions. The test condition of the interface between the ball and the finger were varied as follows: dry without powder, dry with rosin powder, wet without powder, and wet with rosin powder. The results indicated that the powder tended to rather reduce the friction coefficient under dry and wet conditions. The powder also reduced the effect of normal load and sliding velocity on the friction coefficient under dry and wet conditions, suggesting that rosin powder stabilizes friction between a finger and a baseball ball.