题目

如图所示，在真空中有一水平放置的不带电平行板电容器，板间距离为d，电容为C，上极板B接地，现有大量质量均为m，带电荷量为q的小油滴，以相同的初速度持续不断地从两板正中间沿图中虚线所示方向射入，第一滴油滴正好落到下极板A的正中央P点。能落到A极板的油滴仅有N滴，且第N＋1滴油滴刚好能飞离电场，假设落到A极板的油滴的电荷量能被极板全部吸收，不考虑油滴间的相互作用，重力加速度为g，则A. 落到A极板的油滴数N＝B. 落到A极板的油根据下列句子单词首字母或所给汉语注释，在横线上写出空缺处各单词的正确形式。（每空只写一词）【1】After the police arrested him, they went to the thief’s house to （追回）the stolen jewelry.【2】Some adverts about __________（环境）protection cater for our conscience or our desire to be respectable citizens.【3】Though he has retired, still he reads newspapers every day to keep himself i of the latest news.【4】Oh, I’ve put on weight recently. I should eat less and take exercise on a r basis.【5】As we know, Wardian cases improved the __________ （存活） rates of plants transported long distances.【6】In the center of the b of flats, there is a small courtyard where I can plant some flowers.【7】In France the children place their shoes by the fireplace, a tradition d back to when children wore wooden peasant shoes.【8】I was quite annoyed the other day, with Xiamen Airline c me extra for the overweight luggage.【9】The young girl has been __________（提拔）from an ordinary office clerk to a manager due to her excellent performance.【10】These comments came in r to specific questions often asked by local newsmen.【11】Some cigarette advertisements are not aimed at mature audiences but instead t at children.【12】Another __________（潜在）dangerous sea animal is the jelly fish, which can cause severe pain to anyone who touches them.【13】If an alarm is s , do get out of the water as quickly as possible, as sharks are spotted nearby.【14】Many countries have a government organization to deal with customers’ __________（投诉）about ads.【15】Teaching as a career ____________（吸引）to many young people because of the long holiday.