如圖所示,在方向豎直向下的勻強(qiáng)電場(chǎng)中,一絕緣輕細(xì)線一端固定于O點(diǎn),另一端系一帶正電的小球在豎直平面內(nèi)做圓周運(yùn)動(dòng).小球的電荷量為q,質(zhì)量為m,絕緣細(xì)線長(zhǎng)為L(zhǎng),電場(chǎng)的場(chǎng)強(qiáng)為E.若帶電小球恰好能通過(guò)最高點(diǎn)A,則( )
![](http://thumb.zyjl.cn/pic6/res/GZWL/web/STSource/2017113006052263085801/SYS201711300605264256264259_ST/SYS201711300605264256264259_ST.001.png)
A.在A點(diǎn)時(shí)小球的速度v1= ![](http://thumb.zyjl.cn/pic6/res/GZWL/web/STSource/2017113006052263085801/SYS201711300605264256264259_ST/SYS201711300605264256264259_ST.002.png)
B.在A點(diǎn)時(shí)小球的速度v1= ![](http://thumb.zyjl.cn/pic6/res/GZWL/web/STSource/2017113006052263085801/SYS201711300605264256264259_ST/SYS201711300605264256264259_ST.003.png)
C.運(yùn)動(dòng)到B點(diǎn)時(shí)細(xì)線對(duì)小球的拉力為6(mg+qE)
D.小球運(yùn)動(dòng)到最低點(diǎn)B時(shí)的速度v2=![](http://thumb.zyjl.cn/pic6/res/GZWL/web/STSource/2017113006052263085801/SYS201711300605264256264259_ST/SYS201711300605264256264259_ST.004.png)