In fall 2006，the National Basketball Association （NBA）started using basketballs made with synthetic ，or man-made ，material instead of leather（皮革）．They made the change be- cause they wanted every basketball they use to feel and bounce（彈起）the same．Not all leather balls are exactly alike in weight or how they bounce，but the synthetic balls are．

However，some players complained right away that the new balls bounced differently and were actually harder to control than the leather ones．

Physics helped answer questions about why the new balls felt different．For example，the scientists studied friction（摩擦力），which in this case affects the ability of a player to hold onto a ball．"The greater the friction，the better it will stick to his hand，"explains a scientist．

Tests on both wet and dry balls showed that while the synthetic ball was easier to hold onto when dry，it had less friction and became much harder to hold onto when wet．That's because sweat（汗水） stays on the surface of the synthetic balls but gets taken into the leather balls．

The scientists also tested bounce and found that the logo （商標(biāo)）printed on the new balls made their surface uneven（不平） and caused them to bounce a little strangely com- pared with the leather balls．

In January，the NBA went back to using the leather bails．They aren't perfect，but for now，that's just the way the ball bounces．

1．Why were the synthetic balls expected to be used in NBA according to the text?

       A．Because they are easier to control．           B．Because they waste less material．

       C．Because they look exactly alike．             D．Because they feel and bounce alike．

2．The ball is easier to hold on to_________

A．when friction is greater                    B．when friction is less

C．when it is heavier                         D．when it bounces strangely

3．The synthetic ball bounces differently from the leather one mainly because _________

A．it is wet                                  B．it is dry

C．there's a logo on it                       D．its weight remains the same

4．It can be inferred（推斷） from the text that _________．

A．a(chǎn) synthetic ball takes in water faster than a leather ball

B．a(chǎn) leather ball is more difficult to make than a synthetic one

C．a(chǎn) synthetic ball is more expensive than a leather ball

D．a(chǎn) leather ball may increase its weight during a game

5．The underlined word" They" in the last paragraph refers to __________．

A．the synthetic balls                        B．the leather balls

C．the ball players                          D．the scientists

練習(xí)冊系列答案
相關(guān)習(xí)題

科目：初中英語 來源：2012屆江蘇揚(yáng)州中學(xué)教育集團(tuán)初三第一次模擬考試英語試卷（帶解析） 題型：完型填空

Last fall I put a bird feeder outside my window. I thought as soon as I hung up, a great ___16____ beautiful birds would come. Days, weeks and months went by; ____17____, no birds.
I asked many people, why? What was I doing ___18____? “Nothing,” most of them replied. “Just ____19____.” So I waited, waited and waited.
I ____20____ off the deck （露臺）, I changed the feed, I ___21____ the feeders, and I ____22____ made the cat go out the other door! But ____23___ seemed to work. So --- I waited, “with patience and hope. ”
Two months later, early in the morning, I was ____24____. A beautiful bird had been on the bird feeder. All of a sudden, I saw hundreds upon hundreds of birds____25____ from everywhere.
____26____ a beautiful lesson this living thing taught me! “Patience and hope” will ____27____ the most beautiful things in life.
So I keep hoping and waiting, waiting and ___28____. I will try to use this “l(fā)ittle lesson” in ____29____ many other things in my life. I guess, “____30____ is a virtue （美德）” after all.

【小題1】
A．littleB．manyC．muchD．lot
【小題2】
A．soB．becauseC．howeverD．a(chǎn)nd
【小題3】
A．badB．wrongC．wellD．good
【小題4】
A．goB．sitC．watchD．wait
【小題5】
A．wentB．putC．cleanedD．took
【小題6】
A．boughtB．soldC．washedD．took
【小題7】
A．a(chǎn)lwaysB．hardlyC．evenD．sometimes
【小題8】
A．nothingB．everythingC．somethingD．a(chǎn)nything
【小題9】
A．sadB．surprisedC．worriedD．frightened
【小題10】
A．comingB．goingC．leavingD．singing
【小題11】
A．ThatB．WhichC．HowD．What
【小題12】
A．spendB．takeC．bringD．come
【小題13】
A．hopingB．dreamingC．watchingD．a(chǎn)sking
【小題14】
A．soB．suchC．muchD．very
【小題15】
A．dreamB．patienceC．volunteeringD．lesson

查看答案和解析>>

科目：初中英語 來源：2013屆重慶市西南大學(xué)附屬中學(xué)九年級6月（第九次）月考英語試卷（帶解析） 題型：完型填空

完型填空。（每小題2分，共20分）
根據(jù)短文內(nèi)容，從A、B、C、D四個(gè)選項(xiàng)中選出一個(gè)能填入相應(yīng)空格內(nèi)的最佳答案。
Every year thousands of people get hurt or die when they are crossing the road. Most of these people are old people and children. Old people often get hurt or die because  1  can’t see or hear very well. Children usually meet with accidents because they are   2 . They forget to look around   3  they cross the road.
How can we lessen (減少) traffic accidents? All of us must   4  the traffic rules. For the drivers, they shouldn’t drive too fast. If they drive too fast, it will be very difficult to stop the  5 in a very short time. For the pedestrians(行人)，it’s very important to be careful while they are   6  on the road. Therefore, when we walk   7  the road, we must try to walk along the pavements(人行道). We must stop and look   8  ways before crossing the road. Look left first, next look right, and then look left again. Only when we are sure that the road is clear, we can cross it. The right way to cross the road is to walk   9 . It’s not safe to walk too slowly or run fast. If people run across the road, they may   10 . As teenagers, we should try to help children, old people or blind people to cross the road. The last one is that we should never play in the street.

【小題1】
A．weB．theyC．heD．them
【小題2】
A．happyB．youngC．carelessD．sad
【小題3】
A．a(chǎn)fterB．beforeC．a(chǎn)lthoughD．if
【小題4】
A．obeyB．makeC．breakD．set
【小題5】
A．oldB．youngC．carD．train
【小題6】
A．walkingB．drivingC．cleaningD．standing
【小題7】
A．throughB．overC．a(chǎn)crossD．off
【小題8】
A．a(chǎn)llB．bothC．eitherD．neither
【小題9】
A．quicklyB．slowlyC．happilyD．safely
【小題10】
A．fall behindB．fall downC．lie downD．set off

查看答案和解析>>

科目：初中英語 來源：2013-2014學(xué)年浙江省溫州地區(qū)九年級上學(xué)期第一次月考英語試卷（解析版） 題型：其他題

五位病人想去醫(yī)院看病。請閱讀右欄A—F六位�？漆t(yī)生的簡介，根據(jù)五位病人的健康問題為他們選出最合適的�？漆t(yī)生診病，并將對應(yīng)字母寫在序號邊上。（有一項(xiàng)為多余選項(xiàng)）

1.Kent has lots of work to do every day. He can’t fall asleep at night.

2.8-year-old Dongdong has a sweet tooth. He has already had four bad teeth.

3.Linlin’s father just can’t give up drinking.

4.Betty is putting on weight but can’t stop eating.

5.Nina has a high fever because of the flu. She has such a big headache that she can’t go to school.  A. Dr. Yang is good at helping people give up drinking.

B. Dr. Smith has different kinds of false teeth for people who are over 20.

C. Dr. Li is good at treating flu (fever, cough etc.)

D. Dr. Chen has a lot of experience in helping patients get enough sleep.

E. Dr. Wright is always ready to offer help on eating problems.

F. Dr. Liu has great skills in fixing bad teeth and communicating with kids to win their trust.

 

查看答案和解析>>

科目：初中英語 來源：2013-2014學(xué)年北京市石景山區(qū)九年級上學(xué)期期末考試英語試卷（解析版） 題型：閱讀理解

Carmen Arace Middle School is situated in the pastoral town of Bloomfield, Conn., but four years ago it faced many of the same problems as inner-city schools in nearby Hartford: low scores on standardized tests and dropping enrollment（入學(xué)注冊）. Then the school’s hard-driving headmaster, Delores Bolton, persuaded her board to shake up the place by buying a laptop computer for each student and teacher to use, in school and at home. What’s more, the board provided wireless Internet access at school. Total cost: $2.5 million.

Now, an hour before classes start, every seat in the library is taken by students who cannot wait for getting online. Fifth-grade teacher Jen Friday talks about different kinds of birds as students view them at a colorful website. After school, students on buses pull laptops from backpacks to get started on homework. Since the computer arrived, enrollment is up 20%. Scores on state tests are up 35%.

Indeed, school systems in rural Maine and New York City also hope to follow Arace Middle School’s example. Governor Angus King had planned using $50 million to buy a laptop for all of Maine’s 17,000 seventh-graders – and for new seventh-graders each fall.

In the same spirit, the New York City board of education voted on April 12 to create a school Internet portal（入口）, which would make money by selling ads and licensing public school students. Profits（盈利）will also provide e-mail service for the city’s 1.1 million public school students. Profits will be used to buy laptops for each of the school system’s 87,000 fourth-graders. Within nine years, all students in grades 4 and higher will have their own computers.

Back in Bloomfield, in the meantime, most of the kinks have been worked out. Some students were using their computers to visit unauthorized（非法的）websites. But teachers have the ability to keep an eye on where students have been on the Web and to stop them. “That is the worst when they disable you,” says eighth-grade honors student Jamie Bassell. The habit is rubbing off on parents. “I taught my mom to use e-mail,” says another eighth-grader, Katherine Hypolite. “And now she’s taking computer classes. I’m so proud of her!”

1.The example of Carmen Arace Middle School in the passage is used to ______.

A. show the problems schools are faced with today

B. prove that a school without high enrollment can do well

C. express the importance of computers in modern education

D. tell that laptops can help improve students’ school performance

2.According to the writer, students in New York City’s public schools will ______.

A. enjoy e-mail service in the near future

B. make money by selling ads on websites

C. all have their own laptops within nine years

D. become more interested in their studies with laptops

3.The underlined word “kinks” in the last paragraph most probably means ______.

A. plans         B. projects       C. problems      D. products

4.From the passage we learn that ______.

A. a school Internet portal is the key to a laptop program

B. the laptop program also has a good influence on parents

C. students slowly accept the fact their online activities controlled

D. the laptop program in public school is mainly for the eighth-graders

 

查看答案和解析>>

科目：初中英語 來源：2011-2012學(xué)年江蘇揚(yáng)州中學(xué)教育集團(tuán)初三第一次模擬考試英語試卷（解析版） 題型：完型填空

Last fall I put a bird feeder outside my window. I thought as soon as I hung up, a great ___16____ beautiful birds would come. Days, weeks and months went by; ____17____, no birds.

   I asked many people, why? What was I doing ___18____? “Nothing,” most of them replied. “Just ____19____.” So I waited, waited and waited.

   I ____20____ off the deck （露臺）, I changed the feed, I ___21____ the feeders, and I ____22____ made the cat go out the other door! But ____23___ seemed to work. So --- I waited, “with patience and hope. ”

   Two months later, early in the morning, I was ____24____. A beautiful bird had been on the bird feeder. All of a sudden, I saw hundreds upon hundreds of birds____25____ from everywhere.

   ____26____ a beautiful lesson this living thing taught me! “Patience and hope” will ____27____ the most beautiful things in life.

So I keep hoping and waiting, waiting and ___28____. I will try to use this “l(fā)ittle lesson” in ____29____ many other things in my life. I guess, “____30____ is a virtue （美德）” after all.

1.A. little       B. many         C. much        D. lot

2.A. so           B. because      C. however     D. and

3.A. bad          B. wrong        C. well        D. good

4.A. go           B. sit          C. watch       D. wait

5.A. went         B. put          C. cleaned     D. took

6.A. bought       B. sold         C. washed      D. took

7.A. always       B. hardly       C. even        D. sometimes

8.A. nothing    B. everything   C. something   D. anything

9.A. sad    B. surprised          C. worried     D. frightened

10.A. coming  B. going        C. leaving     D. singing

11.A. That        B. Which        C. How         D. What

12.A. spend       B. take         C. bring       D. come

13.A. hoping      B. dreaming    C. watching   D. asking

14.A. so          B. such         C. much        D. very

15.A. dream       B. patience     C. volunteering  D. lesson

 

查看答案和解析>>

同步練習(xí)冊答案