题目内容
AB是竖直平面内的四分之一光滑圆弧轨道,在下端B与水平直轨平滑相切,如图10所示。一小木块自A点起由静止开始沿轨道下滑,最后停在C点。已知圆轨道半径为R,小木块的质量为m,小木块运动到B点时的速度为
,水平直轨道的动摩擦因数为
。(小木块可视为质点)求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242021058352699.png)
(1)小木块经过圆弧轨道的B点和水平轨道的C点时,所受轨道支持力NB、NC各是多大?
(2)B、C两点之间的距离x是多大?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824202104244438.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824202104587440.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242021058352699.png)
(1)小木块经过圆弧轨道的B点和水平轨道的C点时,所受轨道支持力NB、NC各是多大?
(2)B、C两点之间的距离x是多大?
(1)NC=mg(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824202106490704.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824202106490704.png)
试题分析:(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824202107208943.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824202108097950.png)
NC=mg 2分
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824202109236886.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824202110359767.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824202111358719.png)
点评:本题难度较小,在最低点属于圆周运动的一部分,因此支持力和重力两个力的合力提供向心力
![](http://thumb2018.1010pic.com/images/loading.gif)
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