高二英语牛津周报2021-2022第二十七期答案

11.BC【解析】小球从A点运动到B点的过程中,动能不变,根据能量守恒定律可得小球的重力势能增加,则电势能减少,则小球在B点的电势能一定小于小球在A点的电势能,B点的电势小于A点的电势,故A项错误;根据动能定理得- mg lsin0N=0,可得Un= mglsin=mg2,故B项正确;若电场是匀强电场,电场力恒定,到达B点时小球速度仍为v,故小球做匀速直线运动,电场力与重力、支持力的合力为零,则当电场力沿斜面向上时,电场力最小,场强最小,如图所示:mg由平衡条件可得qEm= mosin6=2mg,解得Eamnmg,故C项正确;若该电场是AC边中点处的点电荷Q产生的,点电荷Q到A点的距离小于到B点的距离,由于B点的电势小于A点的电势,则Q一定是正电荷,故D项错误。

Dear JackHow are you doing recently I miss you very muchNow I m so excited that I can't wait to share with you anunforgettable experienceLast Friday, our school held a book sale,aimed toraise same money to help those in need. During the courseof the-after- class activity, we gathered on the playground to2e books, which were collected ahead of time. Luckily, agreat many students took an active part in this program andwe got a large amount of money.I believe our generous help is sure to have a goodeffect on children in need, especially those in themountainous areas or poverty-stricken districts. Throughour efforts, we can not only share what we have with thembut also make their life more colorful. We show our lovewhich makes our world go roundBest wishes to you!oursi hua

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