题目内容
如图甲所示的轮轴,它可以绕垂直于纸面的光滑固定水平轴O转动.轮上绕有轻质柔软细线,线的一端系一重物,另一端系一质量为
的金属杆.在竖直平面内有间距为L的足够长的平行金属导轨PO、EF,在QF之间连接有阻值为R的电阻,其余电阻不计.磁感应强度为B的匀强磁场与导轨平面垂直.开始时金属杆置于导轨下端,将重物由静止释放,重物最终能匀速下降.运动过程中金属杆始终与导轨垂直且接触良好,忽略所有摩擦。
小题1:若重物的质量为M,则重物匀速下降的速度
为多大?
小题2:对一定的磁感应强度B,重物的质量M取不同的值,测出相应的重物做匀速运动时的速度,可得出
实验图线.图乙中画出了磁感应强度分别为
和
时的两条实验图线,试根据实验结果计算
与
的比值。![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082411451221411584.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512089202.gif)
小题1:若重物的质量为M,则重物匀速下降的速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512105184.gif)
小题2:对一定的磁感应强度B,重物的质量M取不同的值,测出相应的重物做匀速运动时的速度,可得出
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512121349.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512136218.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512152218.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512136218.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512152218.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082411451221411584.jpg)
小题1:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512261634.gif)
小题2:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512370835.gif)
小题1:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512386221.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512417281.gif)
则
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512433640.gif)
对
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512386221.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512089202.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512479507.gif)
由以上式子解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512261634.gif)
小题2:由(1)得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512620709.gif)
由
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512121349.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512682499.gif)
所以解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114512370835.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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