题目内容
在水平面上,有一弯曲的槽道
槽道由半径分别为
和R的两个半圆构成.如图所示,现用大小恒为F的拉力将一光滑小球从A点沿槽道拉至B点,若拉力F的方向时时刻刻均与小球运动方向一致,则此过程中拉力所做的功为( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241423468743346.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142346686437.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142346811414.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241423468743346.png)
A.0 | B.FR |
C.![]() | D.2πFR |
C
把圆轨道分成x1、x2、x3、……、xn微小段,拉力在每一段上为恒力,则在每一段上做的功W1=Fx1,W2=Fx2,W3=Fx3,……,Wn=Fxn.拉力在整个过程中所做的功W=W1+W2+……+Wn=F(x1+x2+……+xn)=F(π
+πR)=
πFR.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142346811414.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142346983388.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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