题目内容
如图甲所示,两根足够长的平行光滑金属导轨固定放置在水平面上,间距L=0.2m,一端通过导线与阻值为R=1Ω的电阻连接;导轨上放一质量为m=0.5kg的金属杆,金属杆与导轨的电阻均忽略不计.整个装置处于竖直向上的大小为B=0.5T的匀强磁场中.现用与导轨平行的拉力F作用在金属杆上,金属杆运动的v-t图象如图乙所示.(取重力加速度g=10m/s2)求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241156253711446.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241156253871176.gif)
(1)t=10s时拉力的大小及电路的发热功率.
(2)在0~10s内,通过电阻R上的电量.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241156253711446.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241156253871176.gif)
(1)t=10s时拉力的大小及电路的发热功率.
(2)在0~10s内,通过电阻R上的电量.
(1)0.16W (2)2C
(1)由v-t图象可知:
①
由牛顿第二定律:
②
③
④
⑤
(或由图可知,t=10s时,v=4m/s) ⑥
联立以上各式,代入数据得:
=0.24N ⑦
⑧
(2)
⑨
⑩
⑾
⑿
联立以上各式,代入数据得:
⒀
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115625418622.gif)
由牛顿第二定律:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115625433461.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115625449431.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115625465297.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115625496295.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115625496347.gif)
联立以上各式,代入数据得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115625511621.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115625543624.gif)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115625558405.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115625558299.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115625574472.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115625589712.gif)
联立以上各式,代入数据得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115625605758.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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