题目内容
质量m=3kg的物体,在水平拉力F=6N的拉力作用下,在光滑的水平面上从静止开始运动,运动时间t=3s,求:
(1)力F在3s内对物体所做的功
(2)力F在3s内对物体所做的功的平均功率
(3) 3s末力F对物体所做的功的瞬时功率
(1)力F在3s内对物体所做的功
(2)力F在3s内对物体所做的功的平均功率
(3) 3s末力F对物体所做的功的瞬时功率
(1)54J (2)18W (3) ![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140232133686.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140232133686.png)
根据牛顿第二定律得
3S末的速度为![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140232242873.png)
所以在3s内物体做功为![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241402322891318.png)
力F在3s内对物体所做的功的平均功率![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140232351783.png)
3s末的瞬时功率为![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140232133686.png)
本题考查的是功和功率,一定要分清瞬时功率和平均功率
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140232180798.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140232242873.png)
所以在3s内物体做功为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241402322891318.png)
力F在3s内对物体所做的功的平均功率
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140232351783.png)
3s末的瞬时功率为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140232133686.png)
本题考查的是功和功率,一定要分清瞬时功率和平均功率
![](http://thumb2018.1010pic.com/images/loading.gif)
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