※ 引述《cmvct723d (working on)》之銘言： : ※ 引述《rr444 (earth scrap)》之銘言： : : 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. : 我覺得還是怪怪的ㄟ : 為什麼由上往下揮棒會造成球體的back spin? : 可以用個例子解釋給我聽嗎? : 許多強打者都是用撈的阿(尤其是在打低球時) : 還是能夠打成back spin很強的飛球阿 : 我自己的觀點來看 : 造成back spin的keypoint應該是這樣 : 在進入contact動作 : 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 : 然後雙手是沒有完全伸展開來 : 然後進入max bat speed的那一瞬間 : 也就是雙手用力伸直的動作 : 也就是送球的動作 : 因為circular hand(bat) path的關係雙手會進入交疊的狀態 : http://0rz.tw/bf2x7 : http://0rz.tw/742Bs : http://0rz.tw/152xz : 右手手腕會出現內捻的動作 : 以解剖學來說骨骼肌肉位置就是長這樣 : 再用力的狀況下就是會往內旋轉 : 也就是右手會逆時針轉 : 連帶的棒體bat barrel也會有這種現象 : 用圖解來說明的話 : http://0rz.tw/f32yt : 我是覺得這樣來解讀back spin的成因是比較合理的 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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