题目内容
)如图所示,质量为m=1kg的小球被长L=4m的绳悬挂于O点,悬点距地面高h=6m,将小球拉开某一角度θ(θ<900),无初速释放,到最低点时绳子被钉子挡住,绳子刚好断裂,小球被水平抛出,水平距离x=4m,钉子距悬点的距离为d=3m。(g=10m/s2)
求:(1)绳子能承受的最大拉力?
(2)小球释放点绳与竖直方向的夹角θ?![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241150559452946.gif)
求:(1)绳子能承受的最大拉力?
(2)小球释放点绳与竖直方向的夹角θ?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241150559452946.gif)
(1)
N (2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115055992309.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115055961262.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115055992309.gif)
(1)小球在最低点平抛:
在最低点重力和绳的拉力合力充当向心力,
由牛顿第二定律:
解得:
N
(2)小球从释放到最低点,由动能定理:
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115056117503.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115056132247.gif)
在最低点重力和绳的拉力合力充当向心力,
由牛顿第二定律:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115056164604.gif)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115055961262.gif)
(2)小球从释放到最低点,由动能定理:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115056179763.gif)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115055992309.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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