题目内容
长度L=0.5m的轻杆,一端有一质量m=2kg的小球,轻杆以另一端O为圆心在竖直平面内匀速转动(g=10m/s2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241644378612642.jpg)
(1)若小球以3m/s的速度经过圆轨道的最低点,求轻杆对小球的作用力大小
(2)若小球经过最高点时杆对小球的作用力为16N,求此时小球的速度大小
(2)要使小球通过最高点和最低点时,轻杆对小球的作用力方向相同,轻杆的转数应满足什么条件?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241644378612642.jpg)
(1)若小球以3m/s的速度经过圆轨道的最低点,求轻杆对小球的作用力大小
(2)若小球经过最高点时杆对小球的作用力为16N,求此时小球的速度大小
(2)要使小球通过最高点和最低点时,轻杆对小球的作用力方向相同,轻杆的转数应满足什么条件?
(1)56N(2)1m/s(3)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824164437876627.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824164437876627.png)
试题分析:(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824164438064778.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824164438266195.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824164438532811.png)
(2)拉力
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824164438766801.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824164438266195.png)
支持力
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824164439202778.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824164438266195.png)
(3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241644411065714.png)
点评:杆的模型和绳的模型是在高中常遇到的两种基本模型,这两种模型不一样,杆在最高点的速度可以为零,而绳在最高点时的速度必须大于或等于最小速度.
![](http://thumb2018.1010pic.com/images/loading.gif)
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