题目内容
(9分) 杭州市民吴菊萍徒手勇救小妞妞,被誉为“最美妈妈”。 设妞妞的质量m =10kg,从离地h1 ="21.5" m高的阳台掉下,在妞妞开始掉下时,吴菊萍立刻奔跑到达妞妞的正下方,站立着张开双臂在距地面高度为h2 =1.5m处接到妞妞,缓冲到地面时速度恰好为零。空气阻力不计,取g =10m/s2。求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082423184436755004.png)
(1)妞妞在被接到前下落的时间t1 ;
(2)在缓冲过程中吴菊萍对妞妞做的功W和吴菊萍对妞妞的平均作用力F的大小。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082423184436755004.png)
(1)妞妞在被接到前下落的时间t1 ;
(2)在缓冲过程中吴菊萍对妞妞做的功W和吴菊萍对妞妞的平均作用力F的大小。
(1)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824231848516610.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824231845818506.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824231847206663.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824231848516610.png)
试题分析:(1)妞妞自由下落过程,由运动学公式得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824231849936765.png)
求得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824231845818506.png)
(2)从阳台掉下到地面,对妞妞由动能定理得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824231852635722.png)
求得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824231847206663.png)
设吴菊萍对妞妞的平均作用力大小为F
由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824231855365599.png)
求得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824231848516610.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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