题目内容
将地面上静止的货物竖直向上吊起,货物由地面运动至最高点的过程中,
图像如图所示。以下判断正确的是
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082415173224239337.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151732070340.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082415173224239337.png)
A.前3s内货物处于失重状态 |
B.最后2s内货物处于完全失重状态 |
C.前3s内与最后2s内货物的平均速度相同 |
D.整个过程中货物的机械能一直增加 |
CD
试题分析:根据
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151732320344.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151732382947.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151732491614.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824151732554520.png)
点评:当加速度向下,并且等于g的时候物体才处于完全失重状态,
![](http://thumb2018.1010pic.com/images/loading.gif)
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