题目内容
如图所示,用轻绳将重球悬挂在竖直光滑墙壁上,当轻绳变长时( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241439556041868.png)
A.绳子拉力变小,墙对球的弹力变大 |
B.绳子拉力变小,墙对球的弹力变小 |
C.绳子拉力变大,墙对球的弹力变大 |
D.绳子拉力变大,墙对球的弹力变小 |
B
以小球为研究对象,设绳子与竖直方向夹角为
,绳子变长,绳子与竖直方向夹角减小,绳子的拉力减小,
,夹角减小支持力减小,B对;
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143955713812.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824143955869806.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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