题目内容
如图所示,光滑细杆竖直固定在天花板上,定滑轮A、B关于杆对称,轻质圆环C套在细杆上,通过细线分别与质量为
、
(
)的物块相连.现将圆环C在竖直向下的外力F作用下缓慢向下移动,滑轮与转轴间的摩擦忽略不计.则在移动过程中( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250009042363424.jpg)
A.外力F保持不变
B.杆对环C的作用力不断增大
C.杆对环C的作用力与外力F合力不断增大
D.杆对环C的作用力与外力F合力的方向保持不变
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904189399.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904205337.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904220549.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250009042363424.jpg)
A.外力F保持不变
B.杆对环C的作用力不断增大
C.杆对环C的作用力与外力F合力不断增大
D.杆对环C的作用力与外力F合力的方向保持不变
C
试题分析:A、B设绳子与水平方向的夹角为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904251310.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904267319.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904283365.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904314790.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904329574.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904345561.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904361936.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904251310.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904439427.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904626302.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250009046411235.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904251310.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904688431.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904704357.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000904626302.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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