题目内容
如图所示,A、B两物体用细线连着跨过定滑轮静止,A、B物体的重力分别为40N和10N,绳子和滑轮的质量、摩擦不计。以下说法正确的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241514170541739.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241514170541739.jpg)
A.地面对A的支持力是40N | B.物体A受到的合外力是30 N |
C.测力计示数10 N | D.测力计示数20 N |
D
试题分析:先分析B,B受到重力和绳子的拉力,二力平衡,所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151417070775.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151417132614.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151417195545.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151417304621.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151417366574.png)
点评:先分别对AB受力分析,然后将AB看做一个整体分析
![](http://thumb2018.1010pic.com/images/loading.gif)
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