题目内容
质量为2 kg的物体静止在水平面上,物体与水平面的动摩擦因数为0.1,作用在物体上的水平拉力F随时间的变化如图所示(以向右为正方向)。(g取10 m/s2。)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241542151184456.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154215134163.png)
(1)试求出物体做变速运动时各时间段的加速度?
(2)请画出物体的速度随时间变化的图象.并求出物体在前13s内的位移?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241542151184456.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154215134163.png)
(1)试求出物体做变速运动时各时间段的加速度?
(2)请画出物体的速度随时间变化的图象.并求出物体在前13s内的位移?
(1)加速时:
;减速时: ![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154215664614.png)
(2) 速度随时间变化的图象如下图
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241542158673338.jpg)
物体在前13s内的位移为51m
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154215570593.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154215664614.png)
(2) 速度随时间变化的图象如下图
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241542158673338.jpg)
物体在前13s内的位移为51m
试题分析:(1)加速时:由牛顿第二定律有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154216366708.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241542165531018.png)
减速时: 由牛顿第二定律有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154216616746.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241542167251065.png)
(2)由图可知0~6s匀加速直线运动6s末速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154217052693.png)
因
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154217271811.png)
10~13s匀减速直线运动,末速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154217942640.png)
则速度随时间变化的图象如下图
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241542185343337.jpg)
速度图线与横轴所围的面积为位移,则物体在前13s内的位移
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241542185661056.png)
点评:利用F-t图象和V-t图象的不同时段的受力和运动情况,结合牛顿运动定律,可以分析求解物体的速度、加速度、位移、质量等物理量。
![](http://thumb2018.1010pic.com/images/loading.gif)
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