题目内容
如图所示,AB为斜面轨道,与水平方向成45°角,BC为水平轨道,两轨道在B处通过一段小圆弧相连接,一质量为m的小物块,自轨道AB的A处从静止开始沿轨道下滑,最后停在轨道上的C点,已知A点高h,物块与轨道间的滑动摩擦系数为
,求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241924252323252.jpg)
(1)在整个滑动过程中摩擦力所做的功
(2)施加一平行于接触面外力使物块缓慢地沿原路回到A点所需做的功
(3)小物块经过AB段与BC段时间之比
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192424561296.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241924252323252.jpg)
(1)在整个滑动过程中摩擦力所做的功
(2)施加一平行于接触面外力使物块缓慢地沿原路回到A点所需做的功
(3)小物块经过AB段与BC段时间之比
(1)mgh(2)2mgh(3)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192425763812.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192425763812.png)
试题分析:(1)物块由A运动到C过程,由动能定理有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192426028924.png)
得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192426605792.png)
(2)物块由C经B运动到A过程,据动能定理有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241924273381002.png)
得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192427900943.png)
(3)物块下滑的过程,有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241924283991690.png)
得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192428945759.png)
由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192429772470.png)
得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824192425763812.png)
点评:应用动能定理解决多过程问题时,比较方便,但是需要注意各个过程的始末状态,以及力做功情况
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目