题目内容
(09年东台市期末)弹性轻绳的一端固定在O点,另一端拴一个物体,物体静止在水平地面上的B点,并对水平地面有压力,O点的正下方A处有一垂直于纸面的光滑杆,如图所示,OA为弹性轻绳的自然长度,现在用水平力使物体沿水平面运动,在这一过程中,物体所受水平面的摩擦力的大小的变化情况是
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250003027212188.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250003027212188.jpg)
A.先变大后变小 |
B.先变小后变大 |
C.保持不变 |
D.条件不够充分,无法确定 |
C
试题分析:假设橡皮绳和水平方向夹角
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000302736297.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000302767522.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000302783685.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000302799812.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000302814806.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250003028302121.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250003028452963.jpg)
![](http://thumb2018.1010pic.com/images/loading.gif)
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