题目内容
密度为ρ的液面上浮有一个质量为m的正方体木块,处于静止状态,如图5-5-8所示,正方体木块在液体外的部分高度为木块边长的
.求将木块恰好压入液体中时,液体对木块的浮力所做的功是多少?(木块边长为L)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241204519661802.jpg)
图5-5-8
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120451951225.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241204519661802.jpg)
图5-5-8
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120451982461.gif)
据浮力公式F浮=ρgV排,设木块没入水中的深度为x,则F浮=ρgL2x,可见F浮与x成正比,做F浮-x图象如图1所示,初态时;x=
,F浮=mg,末态时,x=L,F浮=2mg,图线下阴影部分梯形的面积代表F浮做的功,F浮做的是负功,故有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241204520132576.jpg)
F浮=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120452029860.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120451997235.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241204520132576.jpg)
F浮=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120452029860.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目