题目内容
如图,两根长度分别为L1和L2的光滑杆AB和BC在B点垂直焊接,当按图示方式固定在竖直平面内时,将一滑环从B点由静止释放,分别沿BA和BC滑到杆的底端经历的时间相同,则这段时间为( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114825342548.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114825342548.gif)
A.![]() | B.![]() |
C.![]() | D.![]() |
C
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114825514906.gif)
将A、B、C三点构造在以AC连线为直径的竖直圆周上,并且使B点为竖直直径的上端点,设弦AB的倾角为θ,则将滑环由B点释放到A端的过程中环的加速度大小为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114825545712.gif)
由运动学公式得L1=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114825545406.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114825561631.gif)
又圆的直径为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114825576631.gif)
以上各式联立可解得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114825592693.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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