推 ntust661:因為繩子 m = 0 有加速度沒加速度都沒差 10/18 06:53
→ wubohan:如果是這樣為什麼要考慮"力平衡".反正質量是0,永遠都沒有 10/18 08:54
→ wubohan:受力阿! 10/18 08:54
→ spencer90235:其實在高中範圍 繩子的目的主要在於"傳遞力" 10/18 11:10
→ spencer90235:如果質量很小 繩兩端張力的差也非常小 幾乎視為相等 10/18 11:15
→ JAPTX4869:這樣當助教不行喔ㄎㄎ 10/18 21:40
推 jerry78424:助教大大加油啊>_< 10/18 22:39
→ wwll:可以想成繩子是等速度運動嗎 這樣可以解釋繩子不受力 10/19 00:44
→ chungweitw: It accelerates due to gravity. 10/19 00:50
→ chungweitw:It's just F = ma. 10/19 00:50
→ chungweitw:For a small segment of the rope, m = 0 and 10/19 00:51
→ chungweitw:therefore F = 0 while a can take nonzero values.. 10/19 00:51
→ chungweitw:This problem becomes crystal clear if you have 10/19 00:53
→ chungweitw:ever done a problem with considering a massive rope 10/19 00:53
→ wubohan:所以答案是"有加速度?" 那為什麼可以畫力平衡? 10/19 01:21
→ wubohan:PS.樓上似乎有人認識我ㄎㄎ? 10/19 01:21
→ wubohan:再小的問題只要有一點不懂就要搞懂阿!沒有分助不助教吧! 10/19 01:23
→ chungweitw:because the total force one the rope has to zero. 10/19 01:36
→ chungweitw:and the force on the pulley is opposite to the 10/19 01:37
→ chungweitw:force on the rope by the pulley. 10/19 01:38
→ wubohan:如果是合力為零,為何繩子又會有加速度? 10/19 01:40
→ chungweitw:yes. m =0. It's fine.. 10/19 01:42
→ chungweitw:so "a" is undetermined here... 10/19 01:42
→ chungweitw:and it's determined by m1 g = (m1+m2)a 10/19 01:43
→ wubohan:原來如此,感謝您!其實一開始我有想到m=0是力平衡的關鍵 10/19 02:08
→ wubohan:但更解釋的通了!以前解高中題似乎沒有想到~現在更清楚了! 10/19 02:10