我们把杠杆处于______或______状态称为杠杆平衡.

题型:填空题

问题:

我们把杠杆处于______或______状态称为杠杆平衡.

考点:杠杆的平衡条件
题型:填空题

2010年温哥华冬奥会上,中国选手王潆一人获得三枚金牌,并打破世界纪录如图.下列论述错误的是(  )

A.王濛到达终点线后,还继续向前滑行是由于惯性的原因

B.用力蹬冰面加速,原理是“物体间力的作用是相互的”

C.王濛在领奖台上受到的重力与支持力是一对平衡力

D.王濛在领奖台上受到的支持力和对领奖台的压力是一对平衡力

题型:填空题

阅读理解。

     Northern Europeans spend a lot of time in their cold and cloudy winters planning their summer holidays.

They are proud of their healthy color when they return home after the holiday. But they also know that a

certain amount of sunshine is good for their bodies and general health.

     In ancient Greece people knew about the curing powers of the sun, but this knowledge was lost. At the

end of the nineteenth century a Danish doctor, Niels Finsen, began to study the effect of sunlight on certain

diseases, especially diseases of the skin. He was interested not only in natural sunlight but also in man-made

produced rays. Sunlight began to play a more important part in curing sick people.

     A Swiss doctor, Auguste Rollier, made full use of the sun in his hospital at Leysin. Leysin is a small village

high up in the Alps. The position is important, the rays of the sun with the greatest healing power are the

infra-red (红外线的) and ultraviolet (紫外线的) rays; but ultra-violet rays are too easily lost in fog and the

polluted air near industrial towns. Dr. Rollier found that sunlight, fresh air and good food cure a great many

diseases. He was particularly successful in curing certain forms of tuberculosis(结核病) with his"sun-cure".

     There were a large number of children in Dr. Rollier's hospital. He decided to start a school where sick

children could be cured and at the same time continue to learn. It was not long before his school was full.

     In winter, wearing only shorts, socks and boots, the children put on their skis after breakfast and left the

hospital. They carried small desks and chairs as well as their school books. Their teacher led them over the

snow until they reached a slope (斜坡)which faced the sun and was free from cold winds. There they set out

their desks and chairs, and school began.

     Although they wore hardly any clothes, Rollier's pupils were very seldom cold. That was because their

bodies were full of energy which they got from the sun. But the doctor knew that sunshine can also be

dangerous. If, for example, tuberculosis is attacking the lungs, unwise sunbathing may do great harm.

     Today there is not just one school in the sun. There are several in Switzerland, and since Switzerland is

not the only country which has the right conditions, there are similar schools in other places.

1. According to the passage, when did people began to realize sunlight played a more important part in

    the treatment of disease?

A. From ancient times.

B. At the end of the nineteenth century.

C. Not until this century.

D. Only very recently.

2. Why are a Danish doctor and a Swiss doctor mentioned in the second and third paragraphs? 

A. Because they both made use of sunlight to treat illness.

B. Because they were the first people who used sunlight for treatment.

C. Because they were both famous European doctors.

D. Because they used sunlight in very different ways.

3. Dr Rollier set up a "sun-cure" school probably for the reason that _____.

A. most children could stay in his hospital

B. children could study while being treated

C. the school was expected to be full of pupils

D. the school was high up in the mountains

4. What can be inferred from the last paragraph of the passage?

A. "Sun-cure" schools are becoming popular everywhere.

B. Switzerland is the only country where "sun-cure" schools are popular.

C. Proper Conditions are necessary for the running of a"sun-cure" school.

D. "Sun-cure" schools are found in countries

题型:填空题

数字证书通常采用()格式。

A.X.400

B.X.500

C.X.501

D.X.509

题型:填空题

关于高压隔离开关装设地点和方式的说法不合适的是( )。

A.中小型发电机出口一般应装设隔离开关;
B.容量为200MW及以上大型机组与双绕组变压器为单元连接时,其出口一般均应装设隔离开关;
C.在出线装设电抗器的6~10kV配电装置中,当向不同用户供电的两回线共用一台断路器一组电抗器时,每回线上各装一组出线隔离开关;
D.中性点直接接地的自耦变压器中性点接地不必装设隔离开关。

题型:填空题

每个绕组首端与末端之间的电压叫()。

A.额定电压

B.线电压

C.相电压

D.空载电压

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