题目内容
如图所示,质量为m的小球与弹簧Ⅰ和水平细线Ⅱ相连,Ⅰ、Ⅱ的另一端分别固定于P、Q.小球静止时,Ⅰ中拉力大小为F1,Ⅱ中拉力大小为F2,当仅剪断Ⅰ、Ⅱ中的一根的瞬间时,球的加速度a应是 ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241400147901944.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241400147901944.png)
A.若断Ⅰ,则a=g,方向竖直向下 |
B.若断Ⅱ,则a=![]() |
C.若断Ⅰ,则a=![]() |
D.若断Ⅱ,则a=g,方向竖直向上 |
AB
若剪断Ⅰ的瞬间,
,
消失,小球只受重力,所以a=g,方向竖直向下,A正确,若剪断Ⅱ的瞬间,弹簧来不及恢复原长,所以
消失,小球受
和重力,这两个力的合力与
等大反向,所以a=
,方向水平向左,AB正确,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140014931332.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140014978356.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140014978356.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140014931332.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140014978356.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140014837504.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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