题目内容
光滑水平面上并排放置质量分别为m1 =2kg、m2=1kg昀两物块,t=0时刻同时施加两个力,其中F1="2" N、F2="4-2t" N,方向如图所示。则两物块分离的时刻为 ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241604199032772.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241604199032772.png)
A.l s | B.1.5 s | C.2 s | D.2.5 s |
D
试题分析:水平面光滑,则物块不会受到摩擦力。他们的加速度仅由水平外力提供。两个物块贴在一起,他们之间的内力不为0之前,加速度和速度都相同,直到它们的加速度变化为方向相同且大小不同时,开始分离。在开始时刻,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160420044565.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160420153586.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160420262402.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160420465353.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160420730445.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160420824424.png)
之后
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160421027470.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160420262402.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160421448456.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160421557333.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160420465353.png)
t=2.5s时,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160421963564.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160422150524.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160422368549.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160422633565.png)
之后,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160420465353.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160422852344.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160423086315.png)
综上,两物块分离的时间为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160423179484.png)
故选D,
点评:本题容易错解题为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160423367683.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160423491453.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目