题目内容
如图所示,一轻弹簧左端固定在长木板
的左端,右端与小木块
连接,且
、
及
与地面之间接触面光滑,开始时
和
均静止,现同时对
、
施加等大反向的水平恒力
和
,从两物体开始运动以后的整个过程中,对
、
和弹簧组成的系统 (整个过程中弹簧形变不超过其弹性限度),正确的说法是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301325.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301219.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301219.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301325.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301325.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301219.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301325.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301219.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301325.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851426213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851441215.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301219.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301325.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241148514882919.jpg)
A.由于![]() ![]() |
B.由于![]() ![]() ![]() ![]() |
C.由于![]() ![]() ![]() ![]() |
D.当弹簧弹力大小与![]() ![]() ![]() ![]() |
D
本题可采用排除法.F1、F2大于弹力过程,
向右加速运动,
向左加速运动,F1、F2均做正功,故系统动能和弹性势能增加,A错误;当F1、F2小于弹力,弹簧仍伸长,F1、F 2还是做正功,但动能不再增加而是减小,弹性势能在增加,B错;当
、
速度减为零,
、
反向运动,这时F1、F2又做负功,C错误.故只有D正确.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301219.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301325.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301219.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301325.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301219.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114851301325.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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