问题
计算题
如图所示，小球的质量为m，，悬挂小球的丝线与竖直方向成θ角时，小球恰好在场强为E的匀强电场中静止不动，丝线长度为L。
小题1:小球带何种电荷，电量是多少？
小题2:将小球从图示位置拉回到悬线竖直方向电势能如何变化？
小题3:若将小球从竖直方向成θ角的位置缓慢拉回到悬线竖直的方向，则拉力做功多少？
答案
小题1:正电
（
小题2:增大
小题3:
搜题请搜索小程序“爱下问搜题”
如图所示，小球的质量为m，，悬挂小球的丝线与竖直方向成θ角时，小球恰好在场强为E的匀强电场中静止不动，丝线长度为L。
小题1:小球带何种电荷，电量是多少？
小题2:将小球从图示位置拉回到悬线竖直方向电势能如何变化？
小题3:若将小球从竖直方向成θ角的位置缓慢拉回到悬线竖直的方向，则拉力做功多少？
小题1:正电 （
小题2:增大
小题3:
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| Helen Keller was a very bright, beautiful girl. 1 the age of six months she could already say 2 words. But before she was two years old, she was badly ill. She could not see or hear, and soon she could not even talk. Since then Helen had to fight for _ 3 she wanted. When she was six, her parents invited a teacher for her. 4 _ the help of the teacher, she 5 to see and hear the world around her through her 6 .She learned to 7 the books for the blind. The teacher took Helen for long walks, and 8 her about all the beautiful sights. Helen 9 flowers, climbed the trees and smelled a rainstorm before _10 came. She also learned how to swim and _11_ a horse. After she _12 ,she became a famous writer in America. Her first and most famous _13 is The Story of My Life. Her story has _14 new hope to many blind and deaf people. It has given light to 15 in darkness and encouraged them to live and work. | |||
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