题目内容
如图所示,小球沿光滑的水平面冲上一光滑的半圆形轨道,轨道半径为R,小球在轨道的最高点对轨道压力等于小球的重力,问:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241620313802074.png)
(1)画出小球在最高点的受力情况,并指出向心力的来源。(4分)
(2)小球在最高点的速度为多大?(4分)
(3)小球落地时,距最高的水平位移是多少?(6分)
(4)小球落地时速度为多大?(6分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241620313802074.png)
(1)画出小球在最高点的受力情况,并指出向心力的来源。(4分)
(2)小球在最高点的速度为多大?(4分)
(3)小球落地时,距最高的水平位移是多少?(6分)
(4)小球落地时速度为多大?(6分)
(1)向心力由重力与支持力的合力提供 (2)
(3)S=
(4)Vt=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824162032082504.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824162031520583.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824162031832475.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824162032082504.png)
试题分析:(1) 如图所示:向心力由重力与支持力的合力提供
(2)由mg+N=mv2/R , mg=N 得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824162031520583.png)
(3)由S="vt" ,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824162032612650.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824162031832475.png)
(4)由vy=gt ,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824162033096564.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824162033439676.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824162032082504.png)
点评:本题难度较小,在最高点时,由弹力和重力共同提供向心力,处理平抛运动问题时,根据竖直高度求解运动时间,水平方向上做的是匀速直线运动
![](http://thumb2018.1010pic.com/images/loading.gif)
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