题目内容
图3中各摆球可视为质点,各段绳长均为l,摆角均小于10°,(a)图在垂直纸面内摆动,(b)图中电梯匀加速上升,加速度为a,(c)图摆球带正电,磁场垂直纸面向外,(d)图摆球带正电,电场方向向下.以下说法正确的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082413355621912687.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082413355621912687.png)
A.a图中摆球的周期最小 | B.b和d图中摆球的周期不可能相等 |
C.c图中摆球的周期与未加磁场时是相同的 | D.d图中摆球的周期是最大的 |
C
分别求出周期后进行比较,a图
,b图
,c图由于洛仑兹力方向始终与速度方向垂直,不提供向心力,周期依然是
,d图
,C对;
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133556391908.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133556500805.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133556547730.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824133556687817.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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