题目内容
在一个水平面上建立x轴,在过原点O垂直于x轴的平面的右侧空间有一个匀强电场,场强大小
,方向与x轴正方向相同.在O处放一个电荷量
,质量
的绝缘物块.物块与水平面间的动摩擦因数
,沿x轴正方向给物块一个初速度
,如上图所示.(g取
)试求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242148285682240.jpg)
(1)物块向右运动的最大距离.
(2)物块最终停止的位置.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824214821875826.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824214822530717.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824214823872735.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824214825104497.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824214826446649.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824214827647531.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242148285682240.jpg)
(1)物块向右运动的最大距离.
(2)物块最终停止的位置.
(1)0.4 m (2)O点左侧0.2 m
试题分析:(1)设物块向右运动的最大距离为xm,由动能定理得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242148293011258.png)
可求得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824214830487566.png)
(2)因
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824214831735741.png)
由动能定理得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242148329981053.png)
可得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824214834137525.png)
点评:在使用动能定理时,一定要分清楚过程中各个力的做功情况,以及过程的始末动能
![](http://thumb2018.1010pic.com/images/loading.gif)
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