题目内容
将质量为m的重球与较长的细丝线组成单摆,小振幅振动(摆角小于5°)时周期为T。使小球带电量为q的正电后,置于水平向右的匀强电场中,当把它拉至悬点O右方等高处,使线展开并自由释放,它摆至左方当丝线与竖直方向夹角θ=30°时速度恰为零,如所示。求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250002330181952.png)
(1)匀强电场的电场强度。
(2)使小球进行小角度摆动时的平衡位置及周期。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250002330181952.png)
(1)匀强电场的电场强度。
(2)使小球进行小角度摆动时的平衡位置及周期。
(1)E=
mg/3q,(2)60°,T′=(3/4)1/4T。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000233081313.png)
试题分析:(1)在电场中运动时有动能定理
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250002330961057.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000233081313.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000233127740.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000233143779.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000233143497.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000233174951.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000233190818.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000233205723.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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