题目内容
(7分)如图所示,在光滑的水平面上,有一质量为M的长木板,长木板左端放一质量为m(M>m)的物块。现同时给长木板和物块相同大小的初速度v,分别向左、右运动。它们之间的动摩擦因数为
,长木板足够长,不计空气阻力,求:
①物块和长木板相对静止时,物块的速度大小和方向;
②当物块的速度方向发生改变时,长木板的速度大小。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250040330712930.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004033040301.png)
①物块和长木板相对静止时,物块的速度大小和方向;
②当物块的速度方向发生改变时,长木板的速度大小。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250040330712930.jpg)
①
方向向左 ②![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004033087797.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004033071785.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004033087797.png)
试题分析:①设向左为正方向,对物块、长木板系统的运动,由动量守恒定律有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004033103854.png)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004033071785.png)
由于M>m,因此,
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004033134449.png)
②设向左为正方向,物块的速度方向发生改变时也就是速度为0时,由动量守恒定律有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004033181726.png)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004033087797.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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