题目内容
如图所示,两个质量均为m=1kg的物块A、B套在水平粗糙的CD杆上,并用不可伸长的轻绳连接,整个装置能绕过CD中点的轴OO1转动,物块A、B与杆CD间的动摩擦因素μ=0.2,开始时绳子处于自然长度(绳子恰好伸直但无弹力),物块A到OO1轴的距离为r=0.1m,物块B到OO1轴的距离为2r,现让该装置从静止开始转动,使转速ω逐渐增大,但A、B相对于杆一直未滑动,最大静摩擦力可看做等于滑动摩擦力,g=10m/s2,试求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172441217421.png)
(1)当转速![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172441622454.png)
时,杆对B的摩擦力?
(2)轻绳中刚要产生张力时,转速
等于多少?
(3)当转速
时,杆对A的摩擦力?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172441217421.png)
(1)当转速
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172441622454.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172442075538.png)
(2)轻绳中刚要产生张力时,转速
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172442418370.png)
(3)当转速
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172442636737.png)
(1)0.8N(2)
(3)0.4N
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172442995581.png)
试题分析:(1)当转速
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172441622454.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172443463429.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172443666972.png)
(2)绳中刚要产生张力时,对B有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172443884798.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172444118369.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172442995581.png)
(3)当转速
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172444602654.png)
对A有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172444820808.png)
对B有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172445086893.png)
联立解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824172445366603.png)
点评:分析本题的关键是判断谁随着转速增大先达到最大静摩擦力,两物块刚好不滑动时的角速度是多少。
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目