题目内容
如图,木块A叠放在木板B上,A左端用轻绳与墙连接。已知A与B间动摩擦因数为μ,A的质量为m。现将木板B水平抽出。则A受到的B的摩擦力方向___________。若第一次慢慢将B抽出,A受到摩擦力f1,第二次快速将B抽出,A受到摩擦力f2,则f1___________f2。(填>、<或=)。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824132224550484.png)
水平向右,=;
相当于A相对B向左滑动,所以
,方向水平向右,无论是缓慢抽出,还是快速抽出,两者都是滑动摩擦力,
和
都不变化,所以![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824132224706439.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824132224581765.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824132224612301.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824132224659411.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824132224706439.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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