题目内容
如图所示,一小球A与一个白炽灯泡S紧靠在一起,小球在灯泡的右侧,小球可看做质点,灯泡可视为一点光源,P为一个竖直放置的屏幕,P与
光源之间的距离为L,今将小球以水平速V0向右抛出。
(1)试证明小球运动过程中(没有碰
到屏幕)它在屏幕上的影子将沿屏幕向下做匀速运动。
(2)求影的运动速度。![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241220264861407.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412202643972.gif)
(1)试证明小球运动过程中(没有碰
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412202643972.gif)
(2)求影的运动速度。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241220264861407.gif)
(1)证明见解析
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122026501786.jpg)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122026501786.jpg)
如图所示
,做出小球在t时刻形成的影子的光路图.小球在运动过程中做平抛运动,由其运动规律可知:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241220265643886.jpg)
y=
x=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122026689965.gif)
由三角形知识可知:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241220267201019.jpg)
联立以上三式可得:
式中,g、
、L均为常量,表明影的位移与运动的时间成正比
即影的运动为匀速运动.影的运动速度为V=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122026501786.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412202651772.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241220265643886.jpg)
y=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241220265791024.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122026689965.gif)
由三角形知识可知:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241220267201019.jpg)
联立以上三式可得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241220267351084.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122026751945.gif)
即影的运动为匀速运动.影的运动速度为V=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122026501786.jpg)
![](http://thumb2018.1010pic.com/images/loading.gif)
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