问题 选择题

下列运动中,物体机械能不守恒的是:

     

A.物体沿光滑斜面下滑过程中;

  

B.物体沿圆弧匀速下滑过程中;

  

C.人造卫星沿椭圆轨道绕地球运动过程中;

  

D.圆锥摆的摆球在水平面内做匀速圆周运动的过程中;

答案

答案:B

分析:物体机械能守恒的条件是只有重力或者是弹力做功,根据机械能守恒的条件逐个分析物体的受力的情况,即可判断物体是否是机械能守恒

物体沿光滑斜面下滑过程中,只有重力做功,故机械能守恒

物体沿圆弧匀速下滑过程中,动能不变,势能减少,故机械能不守恒

人造卫星沿椭圆轨道绕地球运动过程中,只是动能和势能的相互转化,仅有万有引力做功,故机械能守恒

圆锥摆的摆球在水平面内做匀速圆周运动的过程中,没有力做功,机械能不变,守恒

所以选不守恒的应该是:B

选择题
阅读理解

阅读理解。

     Not all awards are as noble as the Nobel Prize. Even though most countries have a system for recognizing,

honoring and rewarding people who have done something good in their countries, there are now hundreds of

awards and awards ceremonies for all kinds of things.

     The Oscars are probably the most famous, a time for the (mostly) American film industry to tell itself how

good it is, an annual opportunity for lots of big stars to give each other awards and make tearful speeches. But

it's not only films-now there are also Grammies, Brits, the Mercury Prize and the MTV and Q awards for music.

In Britain, a writer who wins the Booker prize can expect to see their difficult, literary novel hit the bestseller lists

and compete with the "Da Vinci Code" for popularity. The Turner Prize is an award for a British contemporary

artist-each year it causes controversy (争论) by apparently giving lots of money to artists who do things like

display their beds, put animals in glass cases or-this year-build a garden shed.

     Shakespeare never won a prize, nor did Leonardo da Vinci or Adam Smith or Charles Dickens. It would be

possible to say, however, that in the past, scientists and artists could win "patronage" from rich people-a king

or a lord would give the artist or scientist money to have them paint their palaces or help them develop new

ways of making money. With the change in social systems across the world, this no longer happens. A lot of

scientific research is now either funded by the state or by private companies. Perhaps awards ceremonies are

just the most recent face of this process. However, there is more to it than that. When a film wins an Oscar,

many more people will go and see it, or buy the DVD. When a writer wins the Nobel Prize, many more people

buy their books. When a group wins the MTV awards, the ceremony is seen by hundreds of thousands of

people across the world. The group sells lots more records.

     Most awards ceremonies are now sponsored by big organizations or companies. This means that it is not

only the person who wins the award who benefits-but also the sponsors. The MTV awards, for example, are

great for publicizing not only music, but also MTV itself! On the surface, it seems to be a "win-win" situation,

with everyone being happy, but let me ask you a question-how far do you think that publicity and marketing are

winning here, and how much sincere recognition of achievement is taking place?

1. Which of the following awards often confuses the public by giving a prize to people who do unusual things? [ ]

A. The Turner Prize.

B. The Booker Prize.

C. The Mercury Prize.

D. The Oscars.

2. From the context of the paragraph we can infer that "patronage" was perhaps _____.[ ]

A an official position in the government

B the works of ancient scientists and artists

C. the professional qualification for a post

D. an old-fashioned form of prize-giving

3. Which of the following questions does the third paragraph mainly give the answer to? [ ]

A. How does the social system in history develop across the world?

B. Why can someone win a prize and why not for someone else?

C. Why have all these awards and awards ceremorues appeared recently?

D. Why did Shakespeare, Leonardo da Vinci, Adam Smith and Charles Dickens never wm prizes?

4. At the end of the text: the writer shows concern about whether _____. [ ]

A. people are really being given credit for what they have done

B. people are happy to do something good for their countries

C. it is worthwhile to launch.so many awards

D. so many awards will continue to be given around the world

5. Which of the following statements is NOT true according to the text? [ ]

A. The Oscars are given to (usually) American film stars and directors.

B. The Booker Prize can help someone who is not usually successful become successful.

C. When people win awards, they usually become richer and more famous.

D. The MTV awards publicize the people who win them more than the people who are giving them.