题目内容
如图所示,在光滑的水平面上放着两块长度相等,质量分别为M1和M2的木板,在两木板的左端分别放有一个大小、形状、质量完全相同的物块。开始都处于静止状态,现分别对两物块施加水平恒力F1、F2,当物块与木板分离后,两木板的速度分别为v1和v2。若已知v1>v2,且物块与木板之间的动摩擦因数相同,需要同时满足的条件是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241528210472607.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241528210472607.jpg)
A.F1=F2,且M1>M2 | B.F1=F2,且M1<M2 |
C.F1>F2,且M1=M2 | D.F1<F2,且M1=M2 |
BD
试题分析:此题研究的是两物体的相对滑动,所以应该用隔离法。板和物体都做匀变速运动,牛顿定律加运动学公式和动能定理都能用,但题中“当物体与板分离时”隐含着在相等时间内物体的位移比板的位移多一个板长,也就是隐含着时间因素,用牛顿运动定律和运动公式解。
AB、若
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152821062439.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152821125433.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152821172461.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152821125433.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152821281315.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152821172461.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152821421344.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152821484826.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152821577852.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152821125433.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152822201790.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152821172461.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152822388807.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152822451555.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152822498451.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152822576437.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152822638485.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152822700532.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152822778447.png)
CD、若
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152822841535.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152822903422.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152822778447.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152822638485.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152822700532.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152822576437.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152823200981.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241528233091009.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824152823387457.png)
故选BD
点评:要去比较一个物理量两种情况下的大小关系,我们应该通过物理规律先把这个物理量表示出来。要把受力分析和牛顿第二定律结合应用。
![](http://thumb2018.1010pic.com/images/loading.gif)
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