题目

补全对话：（其中两个为多余选项） A：What are you doing for vacation? B: _________(1) A:Where are you doing ? B: To Shanghai . A;_________(2) B;It’s very great. A;_________(3) B;Next Sunday morning . A:_____________(4) B;I’m going there with my parents . A;_________(5) B;For seven days . A;I hope  you’ll have a good time . B.Thank you. A:I have no idea .                         B.I’m going sightseeing C.Who are you going with?                 D,How long are you staying in Shanghai? E.What are you thinking of going there?  �如图所示，竖直放置的半圆形绝缘轨道半径为R，下端与光滑绝缘水平面平滑连接，整个装置处于方向竖直向上的匀强电场E中．一质量为m、带电荷量为+q的物块（可视为质点），从水平面上的A点以初速度v水平向左运动，沿半圆形轨道恰好通过最高点C，场强大小为E（E小于）．（1）试计算物块在运动过程中克服摩擦力做的功．（2）证明物块离开轨道落回水平面过程的水平距离与场强大小E无关，且为一常量．