题目内容
(1)球的速度大小。(2)当小球经过最低点时速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120250988302.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241202510192395.jpg)
(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120251035889.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120251050557.jpg)
(1)小球A在最高点时,对球做受力分析,如图D-1所示。重力mg; 拉力F=mg
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241202510502079.gif)
根据小球做圆运动的条件,合外力等于向心力,即:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241202510662276.jpg)
F=mg ②
(2)小球A在最低点时,对球做受力分析,如图所示。重力mg; 拉力F,设向上为正
根据小球做圆运动的条件,合外力等于向心力
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241202510502079.gif)
根据小球做圆运动的条件,合外力等于向心力,即:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241202510662276.jpg)
F=mg ②
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241202510973379.jpg)
(2)小球A在最低点时,对球做受力分析,如图所示。重力mg; 拉力F,设向上为正
根据小球做圆运动的条件,合外力等于向心力
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241202511283911.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241202511441835.jpg)
![](http://thumb2018.1010pic.com/images/loading.gif)
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