题目内容
如图所示,物体受到两个水平恒力F1和F2作用,F1和F2互相垂直,物体沿光滑水平面从A点运动到B点的过程中,位移为s,AB连线与F1间的夹角为α,则下面关于外力做的功的表达式一定正确的是
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145222502969.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145222502969.png)
A.(F1+F2)s | B.F1scos α+F2ssin α |
C.![]() | D.F1ssin α+F2scos α |
B
试题分析:A、
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145222611333.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145222830353.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241452228771268.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145222939339.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145223033404.png)
B、
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145222611333.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145223142761.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145222830353.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145223313782.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145222611333.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145222830353.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145223641799.png)
C、理由同A选项,C选项错误
D、理由同B选项,D选项错误
故选B
点评:容易题。计算合力对物体做功有两种方法,(1)合力做的功等于各力做功的代数和.即
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145223844813.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145223033404.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145224015829.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145224249310.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145224390240.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824145223033404.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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