题目内容
如图所示,光滑水平面上,水平恒力F拉小车和木块一起做匀加速直线运动,它们的加速度都等于a .已知小车质量为M,木块质量为m,木块与小车间的动摩擦因数为
.则在运动过程中
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082421261670014696.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824212616076301.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082421261670014696.png)
A.木块受到的摩擦力大小一定为![]() |
B.小车受到的合力大小为![]() |
C.小车受到的摩擦力大小为![]() |
D.木块受到的合力大小为![]() |
CD
试题分析:把小车和木块看成一个整体,根据牛顿第二定律得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824212620397758.png)
木块水平方向只受静摩擦力,根据牛顿第二定律得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824212621208898.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824212622082684.png)
对小车运用牛顿第二定律得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824212622768628.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824212623954557.png)
故选CD
点评:该题是整体法和隔离法的应用,要求同学们能选择恰当的研究对象运用牛顿第二定律解题.
![](http://thumb2018.1010pic.com/images/loading.gif)
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