题目内容
在光滑水平面上有一静止的物体,现以水平恒力
推这一物体,作用一段时间后,换成相反方向的水平恒力
推这一物体,当恒力
作用时间与恒力
作用时间相同时,物体恰好回到原处,此时物体的动能为24J,则在整个过程中
、
分别对物体做的总功为( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113836816213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113836831215.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113836831215.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113836816213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113836816213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113836831215.gif)
A.6J, 18J | B.8J、16J | C.12J,12J | D.条件不足,无法判定 |
A
设
做功
,
做功
,有
24J,由功定义知
。设两阶段的作用时间都为t,第一阶段的末速度为v,则有
,解之有
="6" J,
="18" J。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113836816213.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113836909344.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113836831215.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113836941347.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113836956442.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113836972572.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113836987950.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113836909344.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113836941347.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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