题目内容
(2011年山东济南联考) 如图2-3-10所示,两球A、B用劲度系数为k1的轻弹簧相连,球B用长为L的细绳悬于O点,球A固定在O点正下方,且点O、A之间的距离恰为L,系统平衡时绳子所受的拉力为F1.现把A、B间的弹簧换成劲度系数较大且为k2的轻弹簧,仍使系统平衡,此时绳子所受的拉力为F2,则F1与F2的大小之间的关系为( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241416392303672.jpg)
图2-3-10
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241416392303672.jpg)
图2-3-10
A.F1>F2 | B.F1=F2 |
C.F1<F2 | D.无法确定 |
B
选B.作出球B受力矢量图,由力矢量三角形与几何三角形OAB相似可得
=
,由于OA、L、mg不变,所以F不变,所以选项B正确.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241416400104609.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141639277589.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824141639386398.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241416400104609.jpg)
![](http://thumb2018.1010pic.com/images/loading.gif)
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