题目内容
(8分)在高1.5 m的光滑平台上有一个质量为2 kg的小球被一细线拴在墙上,球与墙之间有一根被压缩的轻质弹簧。当烧断细线时,小球被弹出,小球落地时的速度方向与水平方向成60°角,则弹簧被压缩时具有的弹性势能为多大?(g=10 m/s2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241546335952283.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241546335952283.jpg)
Ep=10 J
试题分析:由h=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154633907339.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154633969410.png)
落地时,tan60°=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154634047451.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154634125691.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154634188363.png)
由机械能守恒得:Ep=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154633907339.png)
点评:解决本题的关键知道平抛运动在水平方向上做匀速直线运动,在竖直方向上做自由落体运动.平抛运动的时间由高度决定.
![](http://thumb2018.1010pic.com/images/loading.gif)
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