题目内容
质量为m的小球用长为L的轻绳悬于O点,如图所示,小球在水 平力F作用下由最低点P缓慢地移到Q点,在此过程中F做的功为: ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241640111782299.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241640111782299.png)
A.FLsinθ | B.mgLcosθ |
C.mgL(1-cosθ) | D.Fltanθ |
C
试题分析:根据动能定理有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241640115371062.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824164011740913.png)
故选C
点评:本题小球缓慢的由最低点P缓慢地移到Q点,小球受力平衡,拉力F是变力,不能由功的定义式求功,要用动能定理求解。
![](http://thumb2018.1010pic.com/images/loading.gif)
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