题目内容
吊桥AB长L,重G1,重心在中心.A端由铰链支于地面,B端由绳拉住,绳绕过小滑轮C挂重物,重量G2已知.重力作用线沿铅垂线AC,AC=AB.当吊桥与铅垂线的夹角θ=______吊桥能平衡,此时铰链A对吊桥的作用力FA=______.
![](http://thumb.1010pic.com/pic2/upload/papers/20140610/201406102308508943020.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140610/201406102308508943020.png)
以A为支点,根据力矩平衡条件:
G1?
?cos(90°-θ)=G2?Lcos
得:sin
=
得:θ=2arcsin
,
![](http://thumb.1010pic.com/pic2/upload/papers/20140610/2014061023085108112996.png)
以杆为研究对象受力分析,
![](http://thumb.1010pic.com/pic2/upload/papers/20140610/201406102308511283925.png)
由合成法,铰链A对吊桥的作用力FA=(G2cos
)2+(G1-G2)2
由数学知识知:cos2
=1-sin2
整理的:FA=
;
故答案为:2arcsin
;
.
G1?
L |
2 |
θ |
2 |
得:sin
θ |
2 |
G2 |
G1 |
得:θ=2arcsin
G2 |
G1 |
![](http://thumb.1010pic.com/pic2/upload/papers/20140610/2014061023085108112996.png)
以杆为研究对象受力分析,
![](http://thumb.1010pic.com/pic2/upload/papers/20140610/201406102308511283925.png)
由合成法,铰链A对吊桥的作用力FA=(G2cos
θ |
2 |
由数学知识知:cos2
θ |
2 |
θ |
2 |
整理的:FA=
G12-G22 |
故答案为:2arcsin
G2 |
G1 |
G12-G22 |
![](http://thumb2018.1010pic.com/images/loading.gif)
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