试题与答案

如图所示,细线拴一带负电的小球在竖直向下的匀强电场中运动。假设小球所受的电场力q

题型:选择题

题目:

如图所示,细线拴一带负电的小球在竖直向下的匀强电场中运动。假设小球所受的电场力qE与重力G的大小关系为qE=G,且小球运动到最低点a处的速率为va,运动到最高点b处的速率为vb,则va与vb的关系为(   )

A.va>vb

B.va=vb

C.va<vb

D.条件不足,无法确定

答案:

答案:B

题目分析:因为电场力等于重力,所以从a点运动到b点,两力做功之和为零,所以,B正确,

点评:此题是一道简单的粒子在复合场中的运动,关键是从做功的角度分析

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题型:完形填空

第一节 短文填词(共10小题,每小题1分,满分10分)

阅读下面短文,根据以下提示:1)汉语提示; 2)首字母提示;3)语境提示,在每个空格内填入一个适当的英语单词,并将该词完整地写在右边相对应的横线上。所填单词要求意义准确、拼写正确。

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小题1:.

____________

force to ________ the same thing repeatedly; then a habit

小题2:.

____________

is formed. O________ a habit is formed, it’s difficult to get rid of it.

小题3:.

__________

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小题4:.

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小题5:.

____________

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小题7:.

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小题8:.

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小题9:.

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We should k________ from all the bad habits and try to form good ones.   

小题10:.

__________

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