题目内容
在静止的木箱内用细绳b、c系住一个小球d,细绳b水平,细绳c与竖直方向成θ角。当系统静止不动时,两细绳的拉力分别为Tb、Tc,当木箱沿水平方向向左加速运动时,两根细绳中的拉力变化情况是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250004007371159.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250004007371159.png)
A.Tb减小,Tc增大 | B.Tb不变,Tc增大 |
C.Tb增大,Tc不变 | D.Tb和Tc都增大 |
C
试题分析:对小球受力分析,如图,将重力和拉力Tb合成
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250004007535383.png)
根据共点力平衡条件,有
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000400768760.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000400784782.png)
当小球加速时再次对小球受力分析,同上图,将
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000400893351.png)
竖直方向:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000400909725.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000400784782.png)
水平方向:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000400956811.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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