题目内容
半径为
的球形物体固定在水平地面上,球心正上方有一光滑的小滑轮,滑轮到球面
的距离为
,轻绳的一端系一小球,靠放在半球上的
点,另一端绕过定滑轮后用力拉住,使小球静止,如图所示,现缓慢地拉绳,在使小球由
到
的过程中,半球对小球的支持力
和绳对小球的拉力
的大小变化的情况是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250007498392736.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000749590306.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000749605310.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000749621311.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000749636295.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000749636295.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000749605310.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000749777361.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000749777305.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250007498392736.jpg)
A.![]() ![]() |
B.![]() ![]() |
C.![]() ![]() |
D.![]() ![]() |
A
试题分析:以小球为研究对象,分析小球受力情况:重力G,细线的拉力T和半球面的支持力N,作出N、T
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500075005815104.png)
的合力F,由平衡条件得知F=G. 由△NFA∽△AO1O得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000750073910.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000750104758.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000750120725.png)
由题缓慢地将小球从A点拉到B点过程中,O1O,AO不变,O1A变小,得T变小;N不变,A正确
![](http://thumb2018.1010pic.com/images/loading.gif)
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