問題:Two 5-N forces act at the same point. What should the angle between the two forces be if the resultant is aslo 5 N in magnitude?
答案:120
我想知中間計算steps & methods
要求清楚就可~ 如果我有不明白你所寫的地方我會補充~~3Q
F.4 Phy mechanics
2013-10-22 2:51 am
回答 (2)
2013-10-22 3:23 am
✔ 最佳答案
圖片參考：http://imgcld.yimg.com/8/n/HA00388954/o/20131021192014.jpg
由於力是向量要用平衡四邊形的方法去相加，要求 resultant = 5N便會出現上圖的情形，很容易會看出是等邊三角形，120度是必然的結果。
2013-10-22 3:55 am
This problem can also be solved analytically.
Let a be the angle between the resultant force and each of the 5 N force. Thus the angle between the two 5-N forces is 2a.
Resolve each of the 5-N force in direction of the resultant force and add together, we have,
5.cos(a) + 5.cos(a) = 5
i.e. 10.cos(a) = 5
cos(a) = 0.5
a = 60 degrees
Therefore, the angle between the two 5-N forces is 2 x 60 degrees = 120 degrees.
Let a be the angle between the resultant force and each of the 5 N force. Thus the angle between the two 5-N forces is 2a.
Resolve each of the 5-N force in direction of the resultant force and add together, we have,
5.cos(a) + 5.cos(a) = 5
i.e. 10.cos(a) = 5
cos(a) = 0.5
a = 60 degrees
Therefore, the angle between the two 5-N forces is 2 x 60 degrees = 120 degrees.
收錄日期: 2021-04-21 22:41:50
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20131021000051KK00166