新、舊型排球差異性之比較

Abstract

目的: 本研究目的在於探討新型排球及舊型排球在相同空間中不同球皮紋路對飛行軌跡的影響。不同材質球皮的摩擦係數差異。不同材質下的反彈係數差異。方法:飛行軌跡由雙軌發球機將球發出以2D高速攝影機攝錄經tracker分析飛行路徑。摩擦係數由指針式拉壓力計扣在球皮，球皮上方壓重量測出摩擦係數差異。反彈係數是將球體放置80公分高台落下，以2D高速攝影機攝錄經tracker分析反彈高度差異。結果:飛行軌跡(新型排球362cm)(舊型排球333cm)；摩擦係數(新型排球0.846)(舊型排球0.841)；反彈係數(新型排球0.778)(舊型排球0.789)。結論:相同空間不同球皮紋路會造成球體最高點出現的時間不同，新型排球出現最高點快，舊型排球出現較慢。新型排球有2mm小洞，所接觸面積越大摩擦力越好，舊型排球屬光滑面，接觸的摩擦力較低。反彈差異不大，新型排球為雙層材質再避震效果比舊型排球來的好，在舊型排球與地板碰撞後反彈的高度比新型排球來的好一點，如能加上真實選手測試，對於排球訓練有一定的幫助。

Purpose: This dissertation discusses differences between the conventional volleyball and the newly designed one. Several goals have been proposed at this research. The first is, flight paths influenced by different texture of the balls at the same space. The second is the difference of frictional coefficient between various textures. The third is the difference of collision coefficient between various textures. Approach: Flight path is processed by using dual track volleyball serve machine to serve the ball and recording the process, and using “tracker” to do analysis. Frictional coefficient is measured by the means of pressure gauge, which is used to fix the ball and to add some weight on the ball. Collision coefficient is analyzed by falling the ball from 80-cm place and using “tracker” to analyze the video, which is recorded by 2D high speed camera.Result: Flight path is 362cm and 333cm, frictional coefficient is 0.846 and 0.841, and collision coefficient is 0.778 and 0.789, in correspondence to the newly designed volleyball and the conventional one. Conclusion: Time when the ball flies to the highest altitude would be varied by the different textures. The newly designed ball flies to the highest altitude faster the conventional one. The newly designed ball has bigger frictional, since it has 2mm hole spread on the surface. Collision is not so different.

Keywords: Sphere, Flight path, Frictional coefficient, Collision coefficient