题目内容
如图所示,质量均为1kg的两个小物体A、B放在水平地面上相距9m,它们与水平地面的动摩擦因数均为m=0.2,现使它们分别以初速度vA=6m/s和vB=2m/s同时相向运动,重力加速度g取10m/s2。则它们( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241547408781852.jpg)
A.经约0.92s相遇 B.经约1.38s相遇
C.经2s相遇 D.不可能相遇
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241547408781852.jpg)
A.经约0.92s相遇 B.经约1.38s相遇
C.经2s相遇 D.不可能相遇
C
试题分析:两物体在运动过程中的加速度为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154740940751.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154741190938.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154741283966.png)
故1s末两者相距
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154741377735.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154741486645.png)
当物体A停止下来时,运动的距离为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154741564503.png)
所以可得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154741642721.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154741767534.png)
故两者相遇的时间为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154741829550.png)
点评:本题是一道易错性题目,关键是先判断哪一个物体先静止,此时两者是相遇 了,还是没有相遇,若没有相遇,求出间距,此后就是另外一个物体的运动了,千万不能根据两个物体的初速度以及加速度列方程求解
![](http://thumb2018.1010pic.com/images/loading.gif)
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