问题 多选题

如图所示,沿x轴正方向传播的一列横波在某时刻的波形图为一正弦曲线,其波速为200m/s,下列说法正确的是(  )

A.从图示时刻开始,质点b比质点a先到平衡位置

B.从图示时刻开始,经0.01s质点a通过的路程为0.1m

C.若该波传播中遇到宽约3m的障碍物能发生明显的衍射现象

D.若该波波源从O点沿x轴正向运动,则在x=2000m处接收到的波的频率小于50Hz

答案

A、波沿x轴正方向传播,此时b质点振动方向向下,而a质点直接向下向平衡位置运动,则质点a比质点b先到平衡位置.故A错误.

    B、由图λ=4m,则T=

λ
v
=0.02s

      t=0.01s=

1
2
T,经0.01s质点a通过的路程为S=2A=0.1m.故B正确.

    C、λ=4m>3m,能发生明显的衍射现象.故C正确.

    D、若该波波源从O点沿x轴正向运动,则在x=2000m处接收到的波的频率升高,大于50Hz.故D错误.

故选C

阅读理解

任务型阅读。

      In the United States, it is not usual to telephone someone very early in the morning.  If you telephone

him early in the day, while he is taking a shower or having breakfast, the time of the call shows the matter

is very important and requires attention at once. If someone receives a call after 11:00 pm, he thinks it is

a matter of life and death.  The time chosen for the call communicates its importance.

      In social life,   time   plays  a  very  important part.   In  the  USA, guests will feel they are not highly

regarded if the invitation  to  a dinner party is only three or four days before the party date.  But it is not

true in all countries.  In  other  areas of  the world, it may be considered foolish to make an appointment

too early because plans that are made for a date more than a week away will be forgotten. The meaning

of time is different in different parts of the world. Therefore, misunderstandings appear between people

from different cultures that treat time differently. Being on time is thought of highly  in  American  life.  If

people are not on time, they may be regarded as impolite.  In  the  USA,  keeping  business  companies

waiting for an hour is too impolite.  A  person  is  expected to say sorry when he is 5 minutes late. lf he is

less than 5 minutes late, he  will  say a few words of explanation, though perhaps he will not complete the

sentence.

1题判断正误("T"表示正确,"F);2题完成句子;3~4题简略回答问题;5题将文中画线句子译成汉语.

1.  In the USA, it is usual to telephone someone very early in the morning.    [    ]

2.  In the United States, if someone receives a call after 11:00 pm, he thinks it is            

3.  Can you make an invitation more than a week before the date in the USA?

                                                                            

4.  What is thought of highly in American life according to the author?

                                                                            

5.                                                                            

判断题