问题 选择题

一枚炸弹在空中爆炸,形成冲击波向四面八方传播,下面关于波传播过程中各质元的振动情况的说法中正确的是

A.各质元的振动周期都相等,振幅也都相等

B.各质元的振动周期都相等,离爆炸中心越远的质元振幅越小

C.各质元的振幅都相等,离爆炸中心越远的质元振动周期越小

D.离爆炸中心越远的质元振动周期越小,振幅也越小

答案

答案:B

冲击波向四面八方传播,能量向四周传输,振幅是决定振动能量的物理量,说明振幅越来越小,我们听到的声音也是越远处越弱.但振动周期不变.

阅读理解

阅读理解。

     On a warm Monday, Jenny Neilson bought a sandwich and parked her car under some trees. Rolling

down the windows to let in fresh air, she settled back to enjoy her lunch. Suddenly she noticed a big bald man running through the parking lot. Before she came to realize what would happen, the man was there,

shouting through her window, "Get out!"

     Neilson refused.

     Pulling open her door, the man seized her by the neck and hair, and threw her out of the car onto the

ground. She screamed, grabbing her purse and the keys.

     Two reporters of the local newspaper, Robert Bruce and Jeff Jackson, just outside their office building on a break, heard the screams and began running .

     When they reached Neilson's car, the attacker had jumped into the driver's seat and was madly

searching for the keys. Bruce opened the door, and he and Jackson dragged the man out. The attacker

fought back. But even in his cornered panic, he was no match for the two athletic men.

     Reggie Miller, a worker of the local newspaper, heard the screams, too. He rushed back to the office

to phone the police, and then ran back with some plastic ropes-used to tie up newspapers.

     With his arms tied tight behind him, the prisoner looked up and said coldly, "I hope you guys feel

good about yourselves-you just caught one of the most wanted men." They ignored him and waited for

the police. Later, Bruce and Jackson were shocked to learn the man was the professional carjacker (劫

车者)and suspected murderer, whose picture-but with a full head of hair-had been recently printed in

their own newspaper.                                                                                                                              

     Neilson considers herself lucky though she suffered injuries. She believes the story might have had a

different ending if those good people had not come to her aid. "Unfortunately," she said, "many people

would never have done what they did, and that is the real truth."

1. The underlined word "bald" in Paragraph 1 most probably means     .  

A. strong      

B. without hair    

C. ugly    

D. rude

2. Please arrange the time order of the following events according to the passage.

a. Neilson was enjoying her lunch in the car.

b. A man robbed Neilson of her car.

c. The picture of the carjacker was printed in the local news paper.

d. The carjacker was caught.

A. abcd    

B. dbca      

C. cabd        

D. abdc

3. According to the passage , which of the following statements is True?

A. The two reporters reported the story of the carjacker.

B. The two reporters recognized the carjacker as soon as they saw him.

C. Reggie Miller is also a reporter of the local newspaper.

D. The carjacker was a suspected murderer the police had been searching for.

4. What can be inferred from the last paragraph?

A. Neilson considers herself lucky because she was not badly hurt.

B. Neilson doesn't think many people will do the same as the three men.

C. Neilson thinks everyone will do the same as the three men.

D. Neilson has great confidence in people's kindness and bravery.

5. How is the story organized?

A. According to the order of time.    

B. Accoding to the order of space.

C. By comparison.                

D. By putting forward arguments to support an idea.

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