题目内容
某人用手将质量为1kg的物体由静止向上以a=2m/s2的加速度提升1m,(g取
),则说法正确的是
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134524980568.png)
A.手对物体做功2J |
B.合外力做功2J, |
C.合外力做功12J |
D.物体克服重力做功10J |
BD
人用手使物体由静止上升了1m,所以手对物体做的功包括物体增加的重力势能与增加的动能之和,增加的重力势能为
=10J此时物体的速度根据
得v="2"
,增加的动能为
=2J,所以手对物体做的功为W=12J,A错。物体的加速度为2
由牛顿第二定律
得物体的合外力F=2N,故合外力做功
=Fh=2J,故B对,C错。此过程中重力做功
="mgh=10N" 所以D正确
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134525043795.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134525183554.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134525230443.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134525480872.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134525526501.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134525745435.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134525838423.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134525948460.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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