题目内容
一物体自距地面高H处自由下落,经t落地,此时速度为v,则-------( )
A.t/2时物体距地面高度为H/2 | B.t/2时物体距地面高度为3H/4 |
C.物体下落H/2时速度为v/2 | D.物体下落H/2时速度为![]() |
BD
物体做自由落体运动
,.t/2时物体距地面高度为
,故A错误B正确
设物体下落H/2时速度为
,则有
,
,联立可得
=
v/2,故C错误D正确
故选BD
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123124994639.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241231250101081.png)
设物体下落H/2时速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123125119308.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123125259685.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123125275580.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123125119308.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123124947346.png)
故选BD
![](http://thumb2018.1010pic.com/images/loading.gif)
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