题目内容
如图所示,A、B为同高度相距为L的两点,一橡皮筋的两端系在AB两点,怡好处于原长。将一质量为m的物体用光滑挂钩挂在橡皮筋的中点,物体静止时两段橡皮筋之间的夹角为60°。如果橡皮
筋一直处于弹性限度内,且符合胡克定律,则其劲度系数k为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250003432033001.jpg)
A.
B.
C.
D.![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000343281727.png)
筋一直处于弹性限度内,且符合胡克定律,则其劲度系数k为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250003432033001.jpg)
A.
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000343234627.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000343250666.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000343265735.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000343281727.png)
C
试题分析:据题意,当物体m把橡皮筋拉到如图所示位置时,橡皮筋被拉长L,由于挂钩刚好在中点,则A到挂钩位置被拉长L/2,此时物体处于静止状态,其合力为0,则据平衡条件和胡克定律,利用三角形定则有:F=kL/2=mg/2cos30°,k=2
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000343296344.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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