题目内容
质量为60 kg的体操运动员做“单臂大回环”,用一只手抓住单扛,伸展身体,以单杠为轴做圆周运动.如图所示,此过程中,运动员到达最低点时手臂受的拉力大小至少约为(忽略空气阻力,g=10 m/s2) ( ).
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250037082901932.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250037082901932.jpg)
A.600 N | B.2 400 N | C.3 000 N | D.3 600 N |
C
设运动员的重心到单杠的距离为R,在最低点的最小速度为v,则有
mv2=mg·2R,F-mg=![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003708461570.png)
由以上二式联立并代入数据解得F=3 000 N.
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003708446338.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825003708461570.png)
由以上二式联立并代入数据解得F=3 000 N.
![](http://thumb2018.1010pic.com/images/loading.gif)
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