问题 选择题

一列简谐波横波在x轴上传播,在某时刻的波形如图所示.已知此时质点F的运动方向向下,则下列判断正确的是:(  )

A.此波沿x轴正方向传播

B.质点H此时向上运动

C.质点B将比质点C先回到平衡位置

D.质点E振幅为零

答案

A、简谐波横波在x轴上传播,此时质点F的运动方向向下,可判断出波x轴负方向传播.故A错误.

    B、质点H此时的运动方向与F的运动方向相反,即向上运动.故B正确.

    C、此时质点B向上运动,而质点C向下运动,直接回到平衡位置,则C先回到平衡位置.故C错误.

    D、此时质点E的位移为零,但振幅不为零,各个质点的振幅均相同.故D错误.

故选B

阅读理解

阅读理解。

       Mobile phone has become a problem for middle schools. Some middle schools in Australia

have banned (禁止) students from carrying mobile phones during school hours.

       Mobile phone use among children has become a problem for the schools this year. Several

children have got mobile phones as Christmas presents, and more students want them.

       Mary Bluett, an official (官员) said mobile phone use is a distraction (分心) to students during

school hours and it also gives teachers so much trouble in their classrooms. Teachers were also

saying that sometimes students might use phone messages to cheat (作弊) during exams.

       The official said some schools had tried to ban mobile phones. Some parents felt unhappy

because they couldn't get in touch with their children.

       Many teachers said students should not have mobile phones at school, but if there was a good

reason, they could leave their phones at school office. They also said there were many reasons why

the students should not have mobile phones at school: they were easy to lose and were a distraction

from studies.

       Many people say that they understand why parents would like their children to have phones, but

they think schools should let the students know when they can use their mobile phones.

1. Have some middle schools in Australia banned students from carrying mobile phones at school?

    ______________________________________

2. Probably from whom did some children get mobile phones?

    ______________________________________ 

3. What did some students use phone messages to do? 

    ______________________________________

4. Why did some parents feel unhappy about banning mobile phones at school? 

    ______________________________________

5. Can students use mobile phones for some special reasons?

     ______________________________________

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