题目内容
放在水平地面上静止木块,质量为2kg,在水平方向受到F=10N的拉力作用,木块与地面间的动摩擦因数为0.3,g取10m/s2求:
(1)木块的加速度
(2)木块在4s内的平均速度
(3)若拉力F在6s时撤去,木块在撤去F后还能滑行多远?
(1)木块的加速度
(2)木块在4s内的平均速度
(3)若拉力F在6s时撤去,木块在撤去F后还能滑行多远?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161327901502.png)
试题分析:(1)根据牛顿第二定律
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161328073673.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161328354984.png)
(2)由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161328619628.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161328759493.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161329024702.png)
(3)撤去拉力时物体的速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161329321670.png)
撤去拉力后木块的加速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241613295861062.png)
撤去拉力后木块还能滑行的时间
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161329726706.png)
所以木块在撤去F后还能滑行的距离
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161329960754.png)
点评:在撤掉拉力后,木块的加速度发生了变化,所以要重新求加速度,再者本题还可以用
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161330101652.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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