题目内容
如图,AC、BC为位于竖直平面内的两根光滑细杆,A、B、C恰好位于同一圆周上,C为最低点,a、b为套在细杆上的两个小环,当两环同时从A、B两点由静止开始自由下滑时,下面正确的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241157349002305.gif)
A. a环先到c 点
B. b 环先到c 点
C. 两环同时到达c点
D.无法确定
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241157349002305.gif)
A. a环先到c 点
B. b 环先到c 点
C. 两环同时到达c点
D.无法确定
C
作出辅助线如图所示,设角ACD为
,则AC=CDcos
=2R cos
,
a小球的加速度为g cos
,则
,得
,故C正确
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241157350092165.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115734916201.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115734916201.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115734916201.gif)
a小球的加速度为g cos
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115734916201.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115734978705.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115734994395.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241157350092165.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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