题目内容
如图所示,一个“Y”形弹弓顶部跨度为L,两根相同的橡皮条自由长度均为L,在两橡皮条的末端用一块软羊皮(长度不计)做成裹片。若橡皮条的弹力与形变量的关系满足胡克定律,且劲度系数为k,发射弹丸时每根橡皮条的最大长度为2L(弹性限度内),则发射过程中裹片对弹丸的最大作用力为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241712322742293.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241712322742293.jpg)
A.kL | B.2kL |
C.![]() | D.![]() |
D
试题分析:弹弓发射弹丸的瞬间,受力如图.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241712330544404.jpg)
设裹片对弹丸的弹力分别为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824171233241333.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824171233600353.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824171234006799.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241712343801365.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241712347701008.png)
故选D
点评:力的合成遵循平行四边形定则,由题意可结合等腰三角形的几何知识求解合力..
![](http://thumb2018.1010pic.com/images/loading.gif)
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