题目内容
如图所示,两光滑导轨相距为L,倾斜放置,与水平地面夹角为θ,上端接一电容为C的电容器。导轨上有一质量为m长为L的导体棒平行地面放置,导体棒离地面的高度为h,磁感强度为B的匀强磁场与两导轨所决定的平面垂直,开始时电容器不带电。将导体棒由静止释放,整个电路电阻不计,则( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250005167563121.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250005167563121.jpg)
A.导体棒先做加速运动,后作匀速运动 |
B.导体棒一直做匀加速直线运动,加速度为![]() |
C.导体棒落地时瞬时速度![]() |
D.导体棒下落中减少的重力势能转化为动能,机械能守恒 |
BC
试题分析:设微小时间
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000516803374.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000516881406.png)
则有
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250005168971166.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000516912854.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000516928942.png)
解得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250005169431065.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000516959963.png)
由
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250005169752424.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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