题目内容
质量为m的物体A放在倾角为
的斜面上时,恰好能匀速下滑,现用细线系住物体A,并平行于斜面向上绕过光滑的定滑轮,另一端系住物体B,物体A恰好能沿斜面匀速上滑,求物体的质量。(
)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241147184653884.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114718434267.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114718450673.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241147184653884.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114718481434.gif)
当物体A沿斜面匀速下滑时,受力图如图甲,沿斜面方向的合力为0,f=mgsin
当物体A沿斜面匀速上滑时,受力图如图乙,A物体所受摩擦力大小不变,方向沿斜面向下,沿斜面方向的合力仍为0。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241147184963203.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114718512564.gif)
对物体B![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114718543433.gif)
由牛顿第三定律可知![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114718559280.gif)
由以上各式求出![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114718481434.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114718496200.gif)
当物体A沿斜面匀速上滑时,受力图如图乙,A物体所受摩擦力大小不变,方向沿斜面向下,沿斜面方向的合力仍为0。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241147184963203.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114718512564.gif)
对物体B
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114718543433.gif)
由牛顿第三定律可知
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114718559280.gif)
由以上各式求出
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114718481434.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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