题目内容
如图所示,一光滑的半径为R的半圆形轨道放在水平面上,B点在A点的正上方,一个质量为m的小球以某一速度冲上轨道,当小球到达B点时,小球对轨道的压力恰好为零。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241349555632838.jpg)
(1)求小球到达B点时的速度?
(2)求小球落地点C距A处多远?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241349555632838.jpg)
(1)求小球到达B点时的速度?
(2)求小球落地点C距A处多远?
(1)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241349556251221.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134955578505.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241349556251221.png)
(1)在最高点小球对轨道的压力正好为零,即
(3分)
(2分)
(2)从B点出来后,小球作平抛运动,在竖直方向上
(2分)
即
(1分)
所以在水平方向上:
(2分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134955688711.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134955578505.png)
(2)从B点出来后,小球作平抛运动,在竖直方向上
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134955766676.png)
即
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824134955859643.png)
所以在水平方向上:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241349556251221.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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