题目内容
为了测量列车运行的速度和加速度的大小,可采用如图(a)所示的装置,它是由一块安装在列车头底部的强磁体和埋设在轨道地面的一组线圈及电流测量仪组成的(测量仪未画出)。当列车经过线圈上方时,线圈中产生的电流被记录下来,就能求出列车在各位置的速度和加速度。假设磁体端部磁感强度为B=0.004T,且全部集中在端面范围内,与端面垂直,磁体宽度与线圈宽度相同,且都很小,线圈匝数n=5,长L=0.2m,电阻0.4Ω(包括引线电阻),测试记录下来的电流-位移图象如图(b)所示。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500265003026874.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500265009211516.png)
试求:⑴在离O(原点)30m,130m处列车的速度v1和v2的大小;⑵假设列车是匀变速运动,求列车加速度的大小。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500265003026874.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500265009211516.png)
试求:⑴在离O(原点)30m,130m处列车的速度v1和v2的大小;⑵假设列车是匀变速运动,求列车加速度的大小。
(1)
,![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250026502171023.png)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250026502481132.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250026501081033.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250026502171023.png)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250026502481132.png)
试题分析:(1)列车车头底部的强磁体通过线圈时,在线圈中产生感应电动势和感应电流,根据公式可得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002650264737.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250026502951603.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250026503101593.png)
(2)根据匀速运动公式
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002650326678.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250026503421572.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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