题目内容
如图所示,质量为M的物体穿在离心机的水平光滑滑杆上,M用绳子与另一质量为m的物体相连。当离心机以角速度ω旋转时,M离转轴轴心的距离是r。当ω增大到原来的2倍时,调整M离转轴的距离,使之达到新的稳定状态,则:( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241647418165456.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241647418165456.jpg)
A.M受到的向心力增大 |
B.M的线速度减小到原来的1/2 |
C.M离转轴的距离是 r/2 |
D.M离转轴的距离是r/4 |
BD
试题分析:M做匀速圆周运动的向心力由m的重力提供,m的重力不变,所以M的向心力不变,故A错;一开始有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824164742019527.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824164742238365.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824164742440476.png)
故选BD
点评:解决本题的关键知道再次稳定时,M做圆周运动的向心力不变,根据
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824164742643618.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824164742846456.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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