题目内容
质量为m的两个相同小球A、B穿在水平光滑细杆上,用两根长度为L的轻绳与C球相连,已知C的质量为2m,一开始A、B相距2L,现将系统从静止释放,A与B相碰前瞬间,A、B球的速度大小分别为
、
,下列说法正确的是 ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241405177122072.png)
A.![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140517743716.png)
B.
,![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140517836754.png)
C.轻绳对A球所做的功为![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140517883469.png)
D.C球克服重力所做的功为![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140517930540.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140517587351.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140517649350.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241405177122072.png)
A.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140517743716.png)
B.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140517790720.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140517836754.png)
C.轻绳对A球所做的功为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140517883469.png)
D.C球克服重力所做的功为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140517930540.png)
ACD
本题考查的是对功和能的计算问题,C开始下降到A与B相碰重力对C球做功:
,D正确;由于绳的拉力对A和B做功相等,根据能量守恒,轻绳对A球和B球所做的功均为
,C正确;
,
,A正确,B错误;
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140517930540.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140517883469.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241405180701049.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140517743716.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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