题目内容
如图所示是一种清洗车辆用的手持式喷水枪.设枪口截面积为0.6 cm2,喷出水的速度为20 m/s(水的密度为1×103 kg/m3).当它工作时,估计水枪的平均功率为( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241423488243932.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241423488243932.png)
A.12 W | B.120 W | C.240 W | D.1200 W |
C
1 s内水枪射出的水质量为ρsv,这部分水增加的动能为
,所以水枪的平均功率
ρsv3="240" W.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142348886623.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824142348948463.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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A.12 W | B.120 W | C.240 W | D.1200 W |