题目内容
水滴由屋檐自由下落,当它通过屋檐下高为1.4m的窗户时,用时0.2s,不计空气阻力,g取10m/s2,求窗台下沿距屋檐的高度。
3.2m
试题分析:雨滴自由下落,由题意画出雨滴下落运动的示意图如图所示,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241559433774720.png)
利用自由落体运动的特点和图中的几何关系求解。
如图所示
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155943549687.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155943658703.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155943861602.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155943970565.png)
由①②③④解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241559441891085.png)
代入数据得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155944376519.png)
所以,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241559445941534.png)
点评:本题还可以求出通过窗户的平均速度等于通过时间0.2s的中点时刻的速度,然后算出水滴通过窗台下沿的速度,在根据
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824155944781585.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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