题目内容
质量m=2㎏的物块放在粗糙水平面上,在水平拉力的作用下由静止开始运动,物块动能EK与其发生位移x之间的关系如图所示。已知物块与水平面间的动摩擦因数μ=0.2,重力加速度g取10m/s2,则下列说法正确的是
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241635317821938.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241635317821938.png)
A.x=1m时物块的速度大小为2m/s |
B.x=3m时物块的加速度大小为2.5m/s2 |
C.在前4m位移过程中拉力对物块做的功为9J |
D.在前4m位移过程中物块所经历的时间为2.8s |
D
试题分析:物体在水平方向上受到拉力和摩擦力作用,根据动能定理可得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824163532000841.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824163532266811.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824163532453621.png)
图像的斜率表示合力,在2-4m过程中,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824163532796698.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824163533155904.png)
在前4m位移过程中拉力和摩擦力的合力对物体做功为9J,C错误;
0-2m过程中,物体做加速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824163533389545.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824163533529621.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824163533966628.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824163534184517.png)
故选D
点评:做本题的关键是先写出动能和位移的关系式,根据关系式判断图像斜率等问题
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目