题目内容
从某一高度平抛一物体,当抛出2s后它的速度方向与水平方向成45°角,落地时速度方向与水平成60°角,g取10m/s2。求:
(1)抛出时的初速度;
(2)落地时的速度;
(3)抛出点距地面的高度;
(4)水平射程。
(1)抛出时的初速度;
(2)落地时的速度;
(3)抛出点距地面的高度;
(4)水平射程。
(1)20m/s
(2)40m/s
(3)60m
(4)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123906849599.png)
(2)40m/s
(3)60m
(4)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123906849599.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241239068805166.png)
根据题意画出物体做平抛运动的曲线图如上图所示,设地面高度为h,物体平抛运动落地水平距离为L,时间为t,水平初速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123906911325.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123906927302.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123906958265.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123906973668.png)
水平方向:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123907005465.png)
竖直方向:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123907020651.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123907083457.png)
(1) 当抛出2s后它的速度方向与水平方向成45°角,则此时的高度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241239070981162.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123907145893.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241239071761178.png)
(2) 物体做平抛运动落地时的速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241239072231371.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241239072391507.png)
(3) 抛出点距地面的高度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241239072542120.png)
(4) 物体做平抛运动的水平射程为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241239072851788.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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