题目内容
(8分)如图,质量为40kg的物体受到与水平面成370、大小为200N的拉力F作用,从静止开始运动。力F作用
后撤去。已知物体与水平地面的动摩擦因数
,sin370≈0.6,cos370≈0.8,g取10m/s2。求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241613223161959.jpg)
(1)力F作用过程,物体的加速度大小![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161322332315.png)
(2)撤去F后,物体在水平面上运动的时间![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161322457329.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161321942459.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161322176502.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241613223161959.jpg)
(1)力F作用过程,物体的加速度大小
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161322332315.png)
(2)撤去F后,物体在水平面上运动的时间
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161322457329.png)
(1)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161322878550.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161322628731.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161322878550.png)
试题分析:(1)力F作用过程,物体匀加速
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161323112870.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161323268906.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161323502555.png)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161322628731.png)
(2) 力F撤去时,物体速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161323861471.png)
撤去力F后匀减速过程
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161324017743.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161324235499.png)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824161322878550.png)
点评:本题考查了利用匀变速直线运动规律和牛顿第二定律求解的运动学问题,有代表性。其中关键物理量就是求出加速度。
![](http://thumb2018.1010pic.com/images/loading.gif)
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