题目内容
在半径为R的固定半球形碗内,有一质量为m的物体自碗边向碗底滑动,滑到最低点时速度为v,若物体与碗的动摩擦因数为μ,则物体在最低点受到的摩擦力大小是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192515324755.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192513046620.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192514185892.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192514575888.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192515324755.png)
B
试题分析:滑块经过碗底时,由重力和支持力的合力提供向心力,根据牛顿第二定律得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192515901892.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192517009917.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241925179911430.png)
故选B.
点评:运用牛顿第二定律研究圆周运动物体受力情况,滑块经过碗底时,由重力和碗底对球支持力的合力提供向心力,根据牛顿第二定律求出碗底对球的支持力,再由摩擦力公式求解在过碗底时滑块受到摩擦力的大小.比较基本,不容有失.
![](http://thumb2018.1010pic.com/images/loading.gif)
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