题目内容
如图,质量mA=2.0kg的木板A放在水平面C上,A与C之间的动摩擦因数μ=0.2。木板A右端放着质量m="1.0" kg的小木块B(可视为质点),都处于静止状态。现给木板A一个向右的瞬时冲量使它获得V0="8" m/S的初速度开始运动,当小木块B离开木板A时,木板的速度VA=1.5m/S,木块的速度VB="1" m/S。求:
(1)小木块B在木板A上运动的时间t?
(2)木板A的长度L=?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241146567973680.jpg)
(1)小木块B在木板A上运动的时间t?
(2)木板A的长度L=?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241146567973680.jpg)
(1)2s (2) 8.5m
对B在A上滑动过程中对A分析设A、B摩擦力为f由动量定理
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114656812742.gif)
由动能定理![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114656844984.gif)
对B分析由动量定理![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114656859553.gif)
由动能定理![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114656875758.gif)
代入数据解得:f="2N " t=2s
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114656968396.gif)
板子长度![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114657000519.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114656812742.gif)
由动能定理
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114656844984.gif)
对B分析由动量定理
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114656859553.gif)
由动能定理
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114656875758.gif)
代入数据解得:f="2N " t=2s
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114656890446.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114656968396.gif)
板子长度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114657000519.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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