题目内容
如图所示,木板质量为M,长度为L,小木块的质量为m,水平地面光滑,一根不计质量的轻绳通过定滑轮分别与M和m连接,小木块与木板间的动摩擦因数为μ.开始时木块静止在木板左端,现用水平向右的力将m拉至右端,拉力至少做功为( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851129701.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851129701.gif)
A.![]() | B.2![]() |
C.![]() | D.![]() |
A
若使拉力F做功最少,可使拉力F恰匀速拉木块,容易分析得出
(此 时绳子上的拉力等于
),而位移为
,所以
.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851207413.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851223365.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851239199.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851239599.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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A.![]() | B.2![]() |
C.![]() | D.![]() |