题目内容
如图所示,间距
的足够长的光滑平行金属导轨与水平面成
角放置,导轨电阻不计,导轨上端连有
的电阻,磁感应强度为
的匀强磁场垂直导轨平面向上,
时刻有一质量
,电阻
的金属棒,以
的初速度从导轨上某一位置
开始沿导轨向上滑行,金属棒垂直导轨且与导轨接触良好,与此同时对金属棒施加一个沿斜面向上且垂直于金属棒的外力
,使金属棒做加速度大小为
的匀减速直线运动,则:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241407206567679.png)
(1)
时,外力
的大小?
(2)若已知金属棒运动从开始运动到最高点的过程中,电阻
上产生的热量为
,求此过程中外力
做的功?
(3)到最高点后,撤去外力
,经过足够长时间后,最终电阻
上消耗的功率是多少?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140719969481.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720016385.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720063569.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720125441.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720172370.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720266547.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720344549.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720422664.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720484366.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720562303.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720609563.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241407206567679.png)
(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720734436.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720562303.png)
(2)若已知金属棒运动从开始运动到最高点的过程中,电阻
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720921310.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720983397.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720562303.png)
(3)到最高点后,撤去外力
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720562303.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140720921310.png)
(1)
(2)
(3)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241407214201052.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140721217540.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140721342694.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241407214201052.png)
(1)
,其中
,得
;
如图受力分析,有
,
其中
,
,![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140721810587.png)
解得:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140721217540.png)
(2)到最高点位移:
,
由动能定理得:
,
其中
,
解得:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140721342694.png)
(3)如图,最后稳定时导体棒速度满足:
,
解得:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140722200573.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241407214201052.png)
本题考查电磁感应与牛顿运动定律和能量的结合,根据导体棒做匀加速运动,求出末速度,求出安培力,在下落过程中根据动能定理求出拉力做功
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140721467561.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140721514651.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140721607629.png)
如图受力分析,有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241407216701016.png)
其中
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140721732631.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140721763664.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140721810587.png)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140721217540.png)
(2)到最高点位移:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140721904946.png)
由动能定理得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241407219661465.png)
其中
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241407220281042.png)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140721342694.png)
(3)如图,最后稳定时导体棒速度满足:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241407221381133.png)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824140722200573.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241407222621199.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241407223099306.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241407214201052.png)
本题考查电磁感应与牛顿运动定律和能量的结合,根据导体棒做匀加速运动,求出末速度,求出安培力,在下落过程中根据动能定理求出拉力做功
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目