题目内容
如下图所示,完全相同的三个木块固定在水平面上,一颗子弹以初速度v水平射入,在木块中做匀减速运动,穿过第三块木块后速度减为零,子弹穿入每一块木块之前的速度之比和穿过每一木块的时间之比为 ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125844167999.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125844167999.png)
A.![]() ![]() ![]() |
B.![]() ![]() ![]() ![]() ![]() |
C.![]() ![]() ![]() ![]() ![]() ![]() |
D.![]() ![]() ![]() ![]() ![]() ![]() |
BD
减速到零的匀变速直线运动,可以做反向的初速度为零的匀加速运动处理。处理匀加速运动,由
得,穿过一块、两块、三块的之间之比为
,则穿过三块木块之间之比为
:
:
=
。有公式
得,
。所以答案选BD。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125845836625.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125845852515.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125845181333.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125845103333.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125845087295.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125846211757.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125846538554.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125846569729.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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