问题 问答题

关于单摆的运动,下列说法中正确的是(  )

A.单摆摆动过程中,摆线的拉力和摆球重力的合力为回复力

B.摆球通过平衡位置时,所受合力为零

C.摆球通过平衡位置时,所受回复力为零

D.摆球摆动过程中,经过最大位移处时所受合力为零

答案

A、单摆在运动过程中的回复力是重力沿圆弧方向上切向分力.故A错误.

    B、对于单摆,在平衡位置,回复力为0,合力不为0.拉力和重力的合力提供圆周运动的向心力.故B错误,C正确.

    D、摆球摆动过程中,经过最大位移处,受重力和拉力,合力不为0.故D错误.

故选C.

完形填空

阅读下面短文,根据所读内容在文后的空格里填上适当的单词或短语。注意:每空不超过三个单词。

My name is Jane. My job is to write stories and newsletters for a magazine. My hobby is traveling and I hope to visit Great Britain one day. I’d like a pen-pal from London, who is interested in discussing the differences between Europe and Asia. I love listening to pop music and playing football.

I’m Manuel. I’m a businessman and have a large  company with many workers and clerks. I’d like to find a pen-pal who is also a businessman and lives in North America. I like using the Internet.

I am working in a university. I speak English, French and Russian. My family name is Jackson but my students usually call me Sarah. I’d like a pen-pal who is fond of language learning working in Oxford University. I don’t like using computers for learning and I believe that true language can only happen in a classroom.

I’m Peter and interested in the differences bet ween East Europe and North America. I love riding my horse and listening to jazz. I usually get up at 7 o’clock and go to school around 7:30 in the morning. I want to find a pen-pal living in Sydney who has the same interest as me.

Cindy is my first name. I’m working in a travel agency. Sometimes I am called Mr. Guide as I am working. I’d like to find a pen-pal who comes from Europe. I like playing the piano and listening to jazz. I’m interested in history, but I don’t like to discuss languages.

Name    Vocation(职业) 小题1:___________    Pen-pal from

Jane   小题2:_____________  Traveling;

listening to pop music and 小题3:____________   

London

小题4: _____________ Businessman Using 小题5:_________    North America

Jackson 小题6: _____________ Teaching    Oxford University

Peter   Student 小题7:____________ and listening to jazz 小题8: _____________

Cindy  小题9: _____________ Playing the piano; listening to jazz; history  小题10:_____________

填空题