题目内容
一次模拟演习中,某特种兵进行了飞行跳伞表演。该伞兵从高空静止的直升飞机上跳下,在t0时刻打开降落伞,在3t0时刻以速度v2着地。他运动的速度随时间变化的规律如图所示。下列结论正确的是
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241553016305556.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241553016305556.png)
A.在0~t0时间内加速度不变,在t0~3t0时间内加速度增大 |
B.降落伞打开后,降落伞和伞兵所受的阻力越来越大K |
C.在t0~3t0的时间内,平均速度![]() |
D.在0~t0时间内降落伞和伞兵的总重力的功率与速度成正比 |
CD
试题分析:v-t图像的斜率表示物体的运动加速度,所以在
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155301801427.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155301864480.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155301864480.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155301864480.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155302113551.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155301723623.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155301801427.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155302425710.png)
点评:本题的B选项很容易出错,切记打开降落伞后,人就开始做减速运动了,所以此过程中阻力大于重力,合力朝上,阻力越来越小,合力越来越小,
![](http://thumb2018.1010pic.com/images/loading.gif)
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