The rockets take astronauts and man-made satellites into space. The satellites are used for communication, weather monitoring and research. But how do satellites stay up without falling down?

There are two opposite forces (力量) acting on the satellite. One of them is the force of gravitation (地心引力), which tries to pull the satellite towards the earth. The other force is created by the rotation (旋轉(zhuǎn)) of the satellite around the earth. This force tries to take the satellite away from the earth. With these two forces, the satellite goes round and round. The gravitational pull of the earth (the force which pulls everything towards the ground) is like a rope which keeps the satellite from flying away.

Everything that goes up has to come down. It is only a matter of time before a satellite comes back to the earth. As time goes by, the satellite loses its speed, which makes the gravitational pull stronger than the force pulling it away. This makes the satellite crash (墜落) down to the earth.

1.Which of the following uses of satellites is NOT mentioned?

A. communication

B. monitoring the weather condition

C. doing some research

D. taking pictures

2.The force that pulls the satellite towards the earth is created by ________.

A. the earth

B. the satellite itself

C. the rotation of the satellite

D. the rope

3.Why can’t the satellites fly away?

A. Because of the force from the earth.

B. Because the satellite is too big.

C. Because of the force created by the rotation of the satellite around the earth.

D. Because people on earth have made ropes to tie the satellites tightly.

4.The satellite will finally crashes down to the earth ________.

A. when it flies faster

B. when its speed slows down

C. when people cut the rope

D. when there is no electricity in it

5.Which of the following is TRUE according to the passage?

A. There are four forces acting on the satellite.

B. The force of gravitation makes the satellite go round and round.

C. As time goes by, the satellite will finally fall down.

D. The satellite will stay in space forever.

練習(xí)冊系列答案
相關(guān)習(xí)題

科目：初中英語 來源：人教版九年級Unit2 I think that mooncakes are delicious周周清 題型：單選題

Should we share the earth ______ animals?

A. and B. with C. in D. at

查看答案和解析>>

科目：初中英語 來源：外研版七年級英語上冊Module 7模塊單元測試卷 題型：單選題

Don't______ the TV.My baby is sleeping now.

A. turn on B. turn off

C. look at D. pick up

查看答案和解析>>

科目：初中英語 來源：2018年秋人教版九年級英語下冊（山西）習(xí)題：Unit12 1第一課時 題型：補(bǔ)全對話7選5

根據(jù)對話內(nèi)容，從方框內(nèi)的選項中選出能填入空白處的最佳選項，其中有兩個為多余選項。

A：Hi，Lisa！Have you ever been late for school?

B：Yes，I have.But only once last term.

A：1.

B：I stayed up watching the football match the evening before，so I overslept the next morning.

A：2.

B：I rushed to the bus stop without breakfast.But unluckily，by the time I got there，the school bus had already left.

A：Poor guy！3.

B：I started walking.Luckily，my uncle drove by and gave me a ride，but I was still late.

A：4.

B：He said I shouldn't stay up so late at night.

A：Yes.He is right.5.

B：That's true.I'll go to bed before ten from now on.

A．What did your teacher say?

B．How did you go to school then?

C．Which bus do you take to go to school?

D．Why were you late?

E．It's bad to sleep too long.

F．You should go to bed early at night.

G．What did you do after you get up?

查看答案和解析>>

科目：初中英語 來源：江蘇省蘇州市2018年中考英語專題練習(xí)《閱讀理解》（3） 題型：閱讀單選

A famous foreign company in China wanted a clerk for its public relation department(公關(guān)部).

A beautiful girl with a master's degree(碩士學(xué)位)went through a lot of challenges and her name was on the list. In the final stage she faced an interview together with another girl. Both of them were outstanding, not only in looks but also in education.

The girl was successful in the interview. It seemed that she would get the chance. At last the examiner asked her, "Can you come to the office next Monday?" Shocked by the unexpected question, the beautiful girl couldn't make a decision at the moment, so she said, "I have to talk with my parents before I give an answer." The examiner felt surprised but said calmly, "If so, let's wait till you are ready."

The next day, the girl came to tell the examiner that her parents had agreed to let her begin work next Monday. But the examiner said regretfully, "Sorry, another suitable candidate(候選人)has got the job. You had better try another place. "The beautiful girl was surprised. She asked for an explanation(解釋) and was told, " What is needed here is a person who knows her own mind."

That was how a good opportunity right under the nose of a beautiful girl ran away.

1.The beautiful girl wanted to ask her parents for advice because .

A. she didn't like the job

B. she didn’t expect the examiner would ask such a question

C. she didn't want to answer the question

D. her parents would be angry if she didn't ask them

2.The examiner regarded as the most important.

A. a person's confidence B. a person's knowledge

C. a person's age D. a person' s beautiful looks

3.The underlined phrase "right under the nose of" probably means .

A. 就在鼻子下 B. 想要得到的

C. 沒有把握的 D. 就在眼前的

4.The best title for the passage above might be__________.

A. Make Decisions With Your Parents

B. A Successful Interview

C. Use Your Own Mind

D. Answer the Examiner's Question Quickly

查看答案和解析>>

科目：初中英語 來源：江蘇省蘇州市2018年中考英語專題練習(xí)《閱讀理解》（3） 題型：閱讀單選

Bill was a boy of 15. His parents went gambling(賭博) day and night. Nobody cared about him. He always failed in his exams.①So his teachers didn't like him, nor did his classmates play with him.

Bill often slept in class because his heart was not in school. He almost gave himself up.

One day, Miss Jones, a new teacher, came to Bill's class. She was a smiling, beautiful woman. Bill was in love! For the first time in his young life, he tried not to take his eyes off his teacher; yet, he still failed.

It was Miss Jones' class. She was asking a question. "I'd like the smartest boy to answer my question. " Then she said 1oudly, "Bill, please! "

Bill was surprised. And he stood up without a word.

"Just try it! I believe you can! "

After school, Miss Jones had a long talk with Bill. She told him that she cared about him and believed in him.

Bill thought a lot that evening. From then on he arrived at school on time every day. Miss Jones helped him with his homework in the afternoon. She even cooked delicious food for him. She told Bill, "Nothing is impossible if you put your heart into it. "

Later, Miss Jones gave another exam. Bill did it with all his heart. He was very excited to find that he had passed the exam.② Now Bill discovered that not only could he learn, but he could do it well. A change took place in Bill's heart.

1.Bill always failed in the exams at first because he .

A. went gambling B. talked in class

C. didn't like his teacher D. almost gave himself up

2.Miss Jones changed Bill by .

A. doing homework for him

B. encouraging and helping him

C. giving Bill another exam

D. cooking delicious food for him

3.From the passage we can learn .

A. Miss Jones was a warm-hearted and responsible teacher

B. Bill's pereats-cared about him very much

C. Miss Jones loved to answer Bill's questions

D. Bill didn't like to play with his classmates

4.Which may be the best title for the passage?

A. Parents' Duty B. A Lazy Boy

C. A Boy's Chance D. A Strict Teacher

查看答案和解析>>

科目：初中英語 來源：江蘇省蘇州市2018年中考英語專題練習(xí)《閱讀理解》（3） 題型：閱讀單選

I came to study in the USA a year ago. Yet I did not know the real American society until I injured in an accident, because after the accident I had to see a doctor and go to court(法院).

After the accident, my roommate called a doctor for me. I was very grateful and decided to repay him one day. But the next day, he asked me to pay him $200 for what he had done. I was very surprised. He had a good reason to charge me, he said. ①And if I wanted to collect money from the person who was responsible(負(fù)責(zé))for my injury, I'd have to have a good lawyer. And only a good doctor can help me get a good lawyer.②Now that he had helped me find a good doctor, it was only fair that I should pay him.

But every time I went to see the doctor, I had to wait about 50 minutes. He would see two or three patients at the same time, and often stop treating one so as to see another, yet he charged me $115 each time. The final examination report was only ten lines, and it cost me $215.

My lawyer was all smiles the first time we met. But after that he avoided seeing me at all. He knew very well the other party was responsible for the accident, yet he hardly did anything. He simply waited to collect his money. He was so irresponsible that I decided not to ask for him again. And he made me pay him $770.

Now I had to act as my own lawyer. Because of my inexperience, I told the insurance company(保險公司)the date I was leaving America. Knowing that, they played for time, and I left without getting a cent.

My experiences taught me two things about America: Firstly, in America money is everything. It is more important than friendship, honor or professional morality. Secondly, foreigners are still being unfairly treated. So when we talk about America, we should see both its good and bad sides.

1.The writer 's roommate offered to help him because .

A. he thought it was a chance to make some money

B. he felt sorry for the writer

C. he knew the doctor was a very good one

D. he wanted the writer to have a good lawyer

2.A good doctor is necessary for the writer to .

A. be properly treated

B. talk with the person responsible for the accident

C. become healthy before he leaves America

D. finally get the responsible party to pay for his injury

3.The underlined word "charge" in this passage means " ".

A. be responsible B. be careful

C. ask for money D. get an answer

查看答案和解析>>

科目：初中英語 來源：2018-2019學(xué)年七年級英語上冊（人教版）Unit 5綜合檢測卷 題型：補(bǔ)全對話7選5

補(bǔ)全對話，方框中有兩個多余選項

A: Let's play basketball.

B: 31.1. Where is your basketball?

A: I don't have a basketball. Do you have one?

B: 32.2. But I have a TV.Let's watch TV.

A: 33.3. Let's play ping?pong. I have a ping?pong ball and a ping?pong bat.

B: Oh, where are they?

A: On the desk. 34.4.

B: No, I don't. But my brother has one. Let's borrow(借) it from him.

A: OK. 35.5.

A. No, that sounds boring.

B. Yes, I do.

C. No, I don't.

D. No, he doesn't.

E. That sounds good.

F. Do you have a ping?pong bat?

G. Let's go.

查看答案和解析>>

科目：初中英語 來源：人教新目標(biāo)八年級英語上冊Unit 3　I 題型：單選題

What makes you________ so outgoing?

A. becomes B. becoming

C. to become D. become

查看答案和解析>>

同步練習(xí)冊答案