题目内容
如图所示,灯重G=20N,AO与天花板间夹角α=30°,BO水平,试求AO,BO两绳受到的拉力各为多大?![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140556462525.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140556462525.png)
解:
=40N ………(4分)
="20"
N ………(4分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140556540977.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140556587965.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140556618341.png)
以结点为研究对象,分析受力情况:三根细线的拉力.重物对O点的拉力等于mg.![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241405566495417.png)
作出力图如图.
根据平衡条件得F1=mgcotθ=20
N
F2=
=40N
本题是常见的绳子悬挂物体的类型,常常选择结点为研究对象,根据平衡条件研究.比较容易.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241405566495417.png)
作出力图如图.
根据平衡条件得F1=mgcotθ=20
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140556618341.png)
F2=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140556774569.png)
本题是常见的绳子悬挂物体的类型,常常选择结点为研究对象,根据平衡条件研究.比较容易.
![](http://thumb2018.1010pic.com/images/loading.gif)
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