题目内容
如图4所示,在质量为M的木箱顶部用一轻弹簧悬挂质量均为m(
)的A、B两物体,箱子放在水平地面上,平衡后剪断A、B间细线,此后A将做简谐运动。当A运动到最高点时,木箱对地面的压力为( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241402421012113.png)
A.
B.
C.
D.![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140242445744.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140242055551.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241402421012113.png)
A.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140242133463.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140242179673.png)
C.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140242226687.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140242445744.png)
A
剪断细线,A做简谐运动,回复力的最大值Fmax=mg.
当A运动到最高点时,F回向下,取最大值,即F回=mg,此时弹簧弹力为零.所以木箱对地面的压力为Mg.
当A运动到最高点时,F回向下,取最大值,即F回=mg,此时弹簧弹力为零.所以木箱对地面的压力为Mg.
![](http://thumb2018.1010pic.com/images/loading.gif)
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