Ответы 2
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к какому соцветию относится,семейство послёновых
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Автор:
jacklynlpbm - 6 лет назад
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Что такое соц?что именно нужно по семейству паслёновых?
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Автор:
powdernem9 - 6 лет назад
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ПОМОГИТЕ СОКРАТИТЬ ТЕКСТ. ВЫДЕЛИВ ОСНОВНОЕ В ТЕКСТЕ В 20-ТИ ПРЕДЛОЖЕНИЯ
TRANSPORTATION FOR THE 21ST CENTURY
1.Experts estimate that in the 21st century we will go by rocket from New York to Tokyo in 30 minutes. We will be able to reach any point on the globe from any other point through tunnels deep in the earth. The prospect is adventurous and exciting.
It’s possible that within the next two or three decades we will be riding in remote-controlled electronic cars.
Trips through metropolitan areas will be made on quiet, swift buses travelling on separate express lines of city streets. Helicopters may carry whole buses loaded with passengers from point to point above city traffic. “Flying crane” helicopters soon may help solve the complicated problem of getting passengers from the centre to the airport and back again.
2.Most of the advances in air transportation will materialize within the next few years. The largest airplane ever designed for commercial service, capable of seating nearly 500 passengers, is already being built.
Supersonic transport prototypes now in development are forerunners of a new generation of 1,800 miles per hour passenger jet-liners.
The “ideal” short-haul air transport is a vertical or short take-off and landing aircraft that can fly 30 to 45 passengers right into the heart of a city or its suburbs trips up to 260 miles.
3.Mankind has entered an age of high speeds, pressures, and temperatures which could be generated and withstood only with the help of new and hitherto unknown materials.
In the 1920s the top speed of an airplane was not more than 200 kilometres per hour, the load per square metre of the wing area was about 50 kilograms. The main construction material was wood. In our day, the speed of aircraft, even passenger planes, is approaching 3,000 kilometres per hour, loads may be as high as 600 kilograms per square metre of wing. The turbine that drives such an aircraft is not only a miracle of design, it is also a miracle of materials strength. Its blades, for example, rotate at a tremendous speed and at the temperature greater than 1,000 Centigrade.
The given examples are sufficient to indicate the complexity of materials studies today and the extent to which progress in the near or more distant future depends on them.
4.Of tremendous importance is the creation of new materials. Chemists engaged in polymer research have produced the world’s best synthetic materials.
Metallurgists studying a new class of aluminium alloys have produced a very durable alloy which is being used in aircraft and rocket engineering. The alloy helps reduce the weight of apparatus substantially, thereby effecting a considerable saving of materials.
Plastics are employed in a number of aircraft engine applications and have successfully displaced metals in jet turbine impellers where the high fatigue resistance of the material is of great importance. If suitable higher temperature plastics were developed, it is quite feasible that turbines will one day be all of plastic construction.
At present a great deal of research and development is being carried out to produce special grades of plastics for space vehicles.
For space travel, resistance to cosmic radiation is an important consideration. Many plastic materials possess this property, and also offer the advantage of light weight. Astronaut couches, space capsules, missile fuel cases are manufactured of plastic materials.
5.Some ideas of rapid air transportation are on the drawing boards, some may never get off. Some are already under way and operational, while others may not take shape until the next decade. But changes are taking place, and there are more to come.
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Предмет:
Английский язык -
Автор:
urbanon47q - 6 лет назад
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Ответов:
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Проанализируйте примеры и определите,чем может быть НЕ в русском языке. Обозначьте морфему или часть речи.
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Предмет:
Русский язык -
Автор:
emersongu9m - 6 лет назад
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Ответов:
1 -
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подскажите сходства и различия птиц-нырцов и птиц-плавцов
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Предмет:
Биология -
Автор:
dustyhorton - 6 лет назад
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Ответов:
1 -
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как вы понимаете фразу дети становятся объектами заботы СРОЧНО ДАЮ 16 БАЛОВ
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Предмет:
Обществознание -
Автор:
grady94 - 6 лет назад
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Ответов:
0 -
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