题目内容
一辆电动玩具车,由静止开始沿平直轨道以加速度
匀加速运动,一段时间
后,立即以加速度
匀减速运动,当速度变为零后,立即掉头(不计掉头所需时间),并保持加速度
不变匀加速原路返回。小车改变加速度后恰好经过相同时间
回到原出发点。则
与
的大小之比( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124806142313.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124806157271.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124806188353.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124806188353.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124806157271.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124806142313.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124806188353.png)
A.1:l | B.1:2 | C.1:3 | D.1:4 |
C
本题抓住两过程中位移大小相等,这个等量,玩具车开始以
匀加速运动,则位移为
,后一个阶段先做匀减速运动后有反向加速,设
为正方向,则位移为
,联立可得
与
的大小之比为1:3
故选:C
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124806142313.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124806438656.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124806188353.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124806516803.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124806142313.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124806188353.png)
故选:C
![](http://thumb2018.1010pic.com/images/loading.gif)
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