题目内容
质量为m的物体静止在水平地面上,起重机将其竖直吊起,上升高度为h时,物体的速度为v
此过程中
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220748196226.png)
A.重力对物体做功为![]() | B.起重机对物体做功为mgh |
C.合外力对物体做功为![]() | D.合外力对物体做功为![]() |
C
试题分析:重力做功和路径无关,只和初末位置的高度差有关,上升高度h时,重力向下做负功
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220752720641.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220753515391.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242207547951036.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824220756121924.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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题目内容
A.重力对物体做功为![]() | B.起重机对物体做功为mgh |
C.合外力对物体做功为![]() | D.合外力对物体做功为![]() |