题目内容
如图为伦敦奥运女子75公斤级挺举比赛中周璐璐举起187公斤的图片,两臂成120°,沿手臂撑的力F及她对地面的压力N的大小分别是(g取10m/s2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250019287052193.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250019287052193.jpg)
A.F=4080N,N=1870N | B.F=2620N,N=1870N |
C.F=750N,N=4080N | D.F=1870N,N=2620N |
D
试题分析:以杠铃为研究对象,分析受力情况:重力mg和运动员两臂对杠铃的作用力F1和F2,作出力图如图.
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250019287206046.jpg)
根据平衡条件得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001928736826.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001928752827.png)
以运动员和杠铃整体为研究对象,分析受力可知:整体受到总重力
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250019287671048.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001928798376.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001928814727.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001928845701.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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如图所示,轻绳上端固定在天花板上的O点,下端悬挂一个重为10N的物体A,B是固定的表面光滑的圆柱体。当A静止时,轻绳与天花板的夹角为300,B受到绳的压力是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250021514922268.png)
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A.5N | B.5![]() | C.10N | D.10![]() |