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下图所示的过程中,人对物体做功的是( ) A. 踢出去的足球在地面上滚动一段距离...
下图所示的过程中,人对物体做功的是( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/CZWL/web/STSource/20131029123443554988306/SYS201310291234435549883006_ST/images0.png)
踢出去的足球在地面上滚动一段距离
B.
![manfen5.com 满分网](http://img.manfen5.com/res/CZWL/web/STSource/20131029123443554988306/SYS201310291234435549883006_ST/images1.png)
运动员举起杠铃
C.
![manfen5.com 满分网](http://img.manfen5.com/res/CZWL/web/STSource/20131029123443554988306/SYS201310291234435549883006_ST/images2.png)
小孩用力推车,车未被推动
D.
![manfen5.com 满分网](http://img.manfen5.com/res/CZWL/web/STSource/20131029123443554988306/SYS201310291234435549883006_ST/images3.png)
背着书包在水平路面上匀速前进
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