※ 引述《cmvct723d (working on)》之铭言： : ※ 引述《rr444 (earth scrap)》之铭言： : : good point. back/fore spin is related to : : the place of the ball is hit as well as : : the way of swing. : : but i don't agree your statement exactly. maybe i don't make myself : : clearly and meslead you. i should say this way. : : if you can control to hit the ball at the smae place : : twice, first time hit the ball by up-to-down swinging and : : the second time by down-to-up instead. i believe, : : the flying distance in the first case will be farther : : than the second time because the back-spin effect. : : for golf, i don't know too much but based on my : : observation, it's more making sense this way. : : when i see a flying golf ball, it is almost no : : spin. that partly results from the way of swing. : : so the problem is if you can hit a golf ball : : by a baseball swing method and hit the ball in the same : : effort and at the same place when teeing ball, i believe : : the ball still can go further. : 我觉得还是怪怪的ㄟ : 为什麽由上往下挥棒会造成球体的back spin? : 可以用个例子解释给我听吗? : 许多强打者都是用捞的阿(尤其是在打低球时) : 还是能够打成back spin很强的飞球阿 : 我自己的观点来看 : 造成back spin的keypoint应该是这样 : 在进入contact动作 : http://0rz.tw/a42xS : http://0rz.tw/092Al : http://0rz.tw/682xn : 可以看到右手手腕是朝向天空 : 然後双手是没有完全伸展开来 : 然後进入max bat speed的那一瞬间 : 也就是双手用力伸直的动作 : 也就是送球的动作 : 因为circular hand(bat) path的关系双手会进入交叠的状态 : http://0rz.tw/bf2x7 : http://0rz.tw/742Bs : http://0rz.tw/152xz : 右手手腕会出现内捻的动作 : 以解剖学来说骨骼肌肉位置就是长这样 : 再用力的状况下就是会往内旋转 : 也就是右手会逆时针转 : 连带的棒体bat barrel也会有这种现象 : 用图解来说明的话 : http://0rz.tw/f32yt : 我是觉得这样来解读back spin的成因是比较合理的 the reason is easy. please see pics at this link. http://www.wretch.cc/album/show.php?i=rr444&b=2&f=1517823788&p=0 when a bat is swung from up-to-down, the force F can break into two components F1, F2. And F2 generates a moment to the center of the ball, making the ball back spin. in the oppisite conditions, the ball spins forward when bat force goes down-to-up. you offer us with a very good point that i know we do that when we play but maybe have no idea why until now you point it out. additional comments on this. http://www.wretch.cc/album/show.php?i=rr444&b=2&f=1517823789&p=1 because the consistence of angular momemtum, a small angular momentum increment from the bat will generate a bigger angular momentum on the ball because the weight of the bat is larger than the ball. so to me (in a very simplying condition), spin effects is determined by F1 and m (angular speed on bat) and W (bat weight). using this relationship, i can accept that some sluggers can make the ball back spin (denoated as "+")as you said. this is because they can generate a bigger angular speed increment than others. so that amount (+) is larger than that amount (-) by F1 (downward) to here, we have to give ourself credits bacause we just explain a lot of things that many pro players and coaches don't know about. --

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