1)圖一,繩子上晾著一件衣服。繩子兩端固定在兩道牆上,其中一條水平,另一條與水平成20° 。
2)圖二,一個質量250g的物體與另一個質量1kg的物體以一根通過玻璃管的輕繩相連接,學生把質量250g的物體沿水平方向旋轉,並使伸出玻璃管的繩子長度保持為0.5m
圖一那一題,兩部分繩子的張力均不同。
而圖二要求繩子的張力,書上指由於1kg物體保持靜止,所以其重量與繩子張力平衡,即繩子的張力=10N。但是,圖二的繩子也能分開兩部分吧,1kg物體只與下半部繩子的張力平衡,不能說上半部繩子張力也是10N吧?那為什麼書上指繩子的張力就是10N?
thx a lot!!
為什麼繩子的張力就是10N,物理高手請進
2014-09-17 2:17 am
回答 (2)
2014-09-17 3:37 am
✔ 最佳答案
Along a string, the tension should be the same. In daigram 1, the middle of the string is acted upon by a force, the weight of the clothes. Thus the point (middle point of the string) appears to be acted by 3 forces to make that point in equilibrium. The existence of the downward force from the clothes weight makes the left and right hand sides of the string be of different tension.
In diagram 2, it is assumed that the top of the glass tube is smooth and thus there is no frictional force acting on the swirling string. The tension along the string would then be the same.
2014-09-17 23:39:00 補充：
Your suppl question:
It is just simply the middle point of the string is acted on by another force.
Just think of the string behaves like a spring.When you grip (or hold tightly) the middle part of the spring, you could extend the two sides of the spring to different lengths,i.e. different tensions.
2014-09-17 2:17 am
圖一: photo.pchome.com.tw/forever2015/141086250892
圖二: photo.pchome.com.tw/forever2015/141086251811
圖二: photo.pchome.com.tw/forever2015/141086251811
收錄日期: 2021-04-11 20:54:14
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20140916000051KK00109