题目内容
如图所示,匀强电场水平向左,带正电物块A沿绝缘水平板向右运动,经P点时动能为200 J,到Q点时动能减少了160 J,电势能增加了96 J.则它再次到P点时的动能为____________J.![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241141327531883.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241141327531883.jpg)
40
据题意由P→Q物体克服摩擦阻力做功W="160" J-96 J="64" J,设由Q到物块速度为零时,克服阻力做功为W′,则有:
=
,故W′="16" J.再回到P点时,电场力做正功,故整个过程电场力做功为零,Ek="200" J-(64 J+16 J)×2="40" J.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114132769409.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114132784325.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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