题目内容
(10分)如图所示,A、B为竖直墙面上等高的两点,AO、BO为长度相等的两根轻绳,CO为一根轻杆,转轴C在AB中点D的正下方,AOB在同一水平面内,∠AOB=120°,∠
COD=60°。在O点处悬挂一个质量为m的物体,系统处于平衡状态,试求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241222325652777.jpg)
(1)绳AO所受到的拉力F1和杆OC所受到的压力F2;
(2)若在O点施加一个力F(图中未画出),要使两绳AO和BO中的张力为零,杆CO位置不变,则F的最小值为多大?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412223255072.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241222325652777.jpg)
(1)绳AO所受到的拉力F1和杆OC所受到的压力F2;
(2)若在O点施加一个力F(图中未画出),要使两绳AO和BO中的张力为零,杆CO位置不变,则F的最小值为多大?
(1)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122232612397.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122232581510.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122232596519.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122232612397.gif)
(1)
2分
2分
解得:
1分
1分
(2)当F 与CO垂直时,F最小,即
2分
F最小=
2分
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122232628520.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122232628601.gif)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122232581510.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122232596519.gif)
(2)当F 与CO垂直时,F最小,即
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122232674507.gif)
F最小=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122232612397.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目