题目内容
如图所示,两根长度不同的细绳,一端固定于O点,另一端各系一个相同的小球,两小球恰好在同一水平面做圆周运动,则( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241905210792109.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241905210792109.jpg)
A.它们做圆周运动的周期相等 |
B.它们所需的向心力跟轨道半径成反比 |
C.它们做圆周运动的线速度大小相等 |
D.A球受绳的拉力较大 |
AD
试题分析:设系A、B两铁球的细线与竖直方向夹角分别为α、β,由图知α>β,又受力分析可知A、B的向心力分别为FA=mgtanα,FB=mgtanβ,根据α>β知FA>FB,D对。由牛顿第二定律知
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241905211111759.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190521438854.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190521735941.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190521984565.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190522265962.png)
点评:本题考查了圆周运动相关的向心力方程的列式求解过程。通过受力分析便能找到向心力来源。
![](http://thumb2018.1010pic.com/images/loading.gif)
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