题目内容
如右图所示,用绳索将重球挂在墙上,不考虑墙的摩擦.如果把绳的长度缩短一些,则球对绳的拉力F1和球对墙的压力F2的变化情况是:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241303138761665.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241303138761665.png)
A.F1增大,F2减小 |
B.F1减小,F2增大 |
C.F1和F2都减小 |
D.F1和F2都增大 |
D
假设绳子与墙壁间的夹角为
,则球对绳的拉力
,球对墙的压力
。绳子缩短,
变大,F1和F2都增大。答案选D。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130313907297.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130313938793.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130313985741.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130313907297.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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题目内容
A.F1增大,F2减小 |
B.F1减小,F2增大 |
C.F1和F2都减小 |
D.F1和F2都增大 |