Dynamic phenomena in a ball handling process using a stick

Abstract

Sticks are one of the oldest tools that human beings have used since ancient times. To clarify the characteristics of sticks as tools, we evaluated the impacts of the length of a stick on the number of rolls when a subject rolled a table tennis ball mounted on the axis of a device by using a stick. While the ball turned round 44.5 ± 18.8 times when rolled directly with a finger, the number of its rolls became smaller as the length of the stick became longer; thus, it was 9.9 ± 6.3 with a stick length of 90 cm when it was rolled with a stick. The number of rolls was found to increase with the force applied to the ball and with the maximum velocity of the stick, and was also affected by a deviation angle α _xz of the resultant force applied to the ball. From these results, it was clarified that the reason why it became difficult to roll a ball when the length of a stick increased was not only that the force applied to the stick was dispersed but also that the direction of the force was difficult to control.