Прочитайте текст за две минуты. Найдите в тексте определение таких понятий, как «смещение», «направление», «скорость».

Scalar and Vector Quantities

Mass, length, time, area, velocity, acceleration —all of these are phys­ical quantities. Whenever we measure one of these, we are finding its magnitude.

The magnitude of a physical quantity is always expressed as some number times some unit of measure. For instance, " the magnitudes" 7 cm, 6 cm², 60 mph are all expressed as numbers " 7, 6, 60" times units of measure of length, area and speed (cm, cm², mph).

" 30 miles" is a measurement of a distance. " 30 miles west" is a meas­urement of displacement. Both have a magnitude of 30 miles. However, the displacement also includes the direction in which it is measured. " 30 mph" is a measurement of speed. " 20 mph south-west" is a measure­ment of velocity. Both speed and velocity have magnitude. Which of the two has direction? (speed or velocity? ) " 35 mph west" is a velocity. " 30 miles west" is a displacement. Quantities which have magnitude only are scalar quantities, while vector quantities have magnitude and direction.

Mass, volume, area, and intervals of time have magnitude only. They are scalar quantities. Force, velocity and acceleration have magnitude and direction. They are vector quantities. The words " velocity" and " speed" are considered as synonyms unless they are used in technical literature. In the language of science there is a difference in their meaning. While the word " speed" means the rate at which distance is covered, the word " ve­locity" means speed in a definite direction. Of the two terms " velocity" is much more often used by physicists, for it is broader and more convenient.

• Соотнесите каждый из терминов в списке А с соответствующей ему величиной в списке В.

A. velocity; a speed; a displacement; a magnitude; a direction В. 30 miles: 30 miles north; 30 mi/hr north; 30 mi/hr; north

• Прочитайте по-английски следующие величины и определите, являются они векторными или скалярными?

90 ft/sec north; 47 miles; 15 cm²; 15 mph 30°; 32 ft/sec² towards the centre of the earth

• Заполните пропуски соответствующими словами.

1. Quantities which are scalar have.. only. 2. Mass, volume, area and intervals of time have magnitude only. They are... quantities. 3. Quantities which have both magnitude and direction are... quantities. 4. Force, velocity and acceleration have magnitude and.... They are.... 5. " 5 miles 30° east or west"; " 10 mph north-east"; " 9.8 m/sec² towards the centre of the earth" are all... quantities because they have both... and.... 6. There are two kinds of physical quantities —.... 7. The measurement of a scalar quantity consists of.... 8. The measurement of a vector quantity consists of....

(4) Conversation Practice

• Answer the questions on Text 29A.

1. What is the text concerned with? 2. What is kinematics? 3. What does kinematics deal with⁷ 4. What is dynamics concerned with? 5. With respect to what parameters does kinematics describe motion? 6. What is the mathematical formula for speed? 7. Are the words " speed" and " velocity" synonyms in technical literature? 8. Which of them is more often used in technical literature and why? 9. What does the word " speed" mean? 10. What does the word " velocity" mean? 11. What distance does light cross in a single minute? 12. How much time does light take to reach the Earth from the Sun? 13. What units are used to measure distances in the solar system / other galaxies? 14. What interesting events that had happened in galaxies thousands of years ago were brought to us not long ago?

• Speak on the following topics:

1. Mechanics as a branch of physics and the object of its study. The subbranches of mechanics.

2. Scalar and vector quantities.

3. Speed of light and time.

(5) Home Exercises

Переведите на русский язык.

1. You will not succeed with your experiments, unless you work hard. 2. Supposing no data are given to us, what shall we do? 3. We could wait for you provided you came on time. 4. If I were you, I wouldn't promise to come on time. 5. If I made a promise, I would certainly keep it. 6. If I hadn't made a promise to come, I wouldn't have kept you waiting for me.

2. Напишите полные ответы на следующие вопросы.

1. What would you do, if you had a day off today? 2. Where would you go, if you had a holiday just now? 3. If you had more time, would you take up sports? 4. If you could do it over again, what profession would you choose?

3. Завершите следующие предложения по своему усмотрению:

1. If you promise to come,.... 2. Even if you were late,.... 3. If you promise to keep the secret,.... 4. If I knew what to expect,.... 5. If you came,....

4. Переведите на английский язык следующие предложения, упот­ребив союз unless — если не:

1. Если мы не учтем (involve) ускорение, описание движения не будет точным. 2. Если мы не сделаем этого допущения, ре­зультат будет неверным. 3. Если не ввести в уравнение силы ус­корения, решение будет неверным. 4. Если не поделить это про­изведение (product) на коэффициент плотности, результат будет неверным.

(3) Reading ЗОЛ

Внимательно прочитав текст, объясните, почему посленыотоновс-кий период называют «золотой порой» изобретателей.

Newtonian Mechanics

In 1987 the world science societies marked the 300th anniversary of the publication of Newton's book Philosophic Naturalis Principia Mathemat-ica. In powerful development of physical argument his book is unequalled in the whole history of science. Mathematically it could only be compared to Euclid's ['juiklidz] Elements. In its physical insight and its effect on scientific ideas it could be compared only to Darwin's Origin of Species ['spi: Ji: z]. It immediately became the bible of the new sciences.

Newton's contribution into the world science was a decisive one in find­ing the mathematical method for converting physical principles into quan­titatively calculable results confirmable by observation, and, conversely, to arrive at the physical principles from such observations.

The instrument by which he did this was the infinitesimal calculus which he used to solve vital questions in physics and taught others to do the same.

By its use it is possible to find the position of a body at any time by a knowledge of the relations between that position and its velocity or

rate of change of velocity at any other time. In other words, once the law of force is known, the path can be calculated. Applied inversely, Newton's law of gravitational force follows directly from Kepler's law of motion. Mathematically they are two different ways of saying the same thing; but whereas the laws of planetary motion seem abstract, the idea of a planet held in its course by a powerful gravity attraction is understandable, even if the gravitational force itself remains a com­plete mystery.

The calculus, as developed by Newton, could be used and was used by him for solving of a great variety of mechanical and hydrodynamic prob­lems. It immediately became the mathematical instrument for all under­standing of variables and motion, and hence of all mechanical engineer­ing, and remained almost the exclusive one until well into the present century. In his Principia Newton did far more than establish the laws of motion of the planets. His object was certainly to demonstrate how uni­versal gravity could maintain the system of the world. But he wished to do this not in the old philosophical way but in the new, quantitative, physical way. He destroyed all previous philosophic conceptions, old and new, and established his own not only the correct but also the most accurate way of accounting for the phenomena. In a word, Newton estab­lished, once and for all, the dynamic view of the universe instead of the static one and showed that the universe was regulated by simple mathe­matical laws.

Though Newton used the calculus in arriving at his results, he was very careful in his Principia and did all the work in the form of classical Greek geometry understandable by other mathematicians and astronomers. The immediate practical consequence of its publication was to provide a sys­tem of calculation enabling the positions of the moon and planets to be determined far more accurately on the basis of a minimum of observations. Three observations, for instance, were sufficient to fix the position of a celestial object for an indefinite future. The proof of this was given soon after Newton's time by his friend Halley in his famous comet, whose return he successfully predicted on the basis of Newton's theories.

ЗАДАНИЯ К ТЕКСТУ

• Выпишите из текста английские эквиваленты следующих русских словосочетаний:

не имеет себе равных; по способности проникновения в мир фи­зики; воздействие на научные идеи; метод преобразования; жизнен­но важные вопросы; примененный в обратной (функциональной) зависимости; полная загадка; большое разнообразие; наиболее точ-

ный способ объяснения явлений; раз и навсегда; практическое след­ствие; небесное тело; темп изменения скорости; машиностроение

• Завершите следующие предложения информацией из текста или по своему усмотрению:

1. Newton's Principia was published.... 2. In it Newton developed....

3. The importance of the theory of gravity can only be compared to....

4. In this work Newton established... and snowed.... 5. Newton developed the mathematical method for.... 6. By means of his infinitesimal calculus it is possible to find.... 7. Newton's calculus can be used for solving a great variety of problems in such fields as.... 8. The first proof of his theory was....

Reading ЗОВ

Прочитав текст за две минуты, скажите, в какой связи упоминает­ся имя великого французского ученого Декарта.

Слова для понимания текста:

intricate ['mtnkit] a — сложный; approach n — подход

Isaac ['aizak] Newton, the man of powerful mathematical ability, was bom into a family of a farmer in 1642, the year Galileo died. The early days of Isaac's life were rather unhappy. The child was so weak and slow-witted (несмышленый) that his grandmother had pity on him and didn't send him to school till the boy was twelve. While at school and later at Cambridge Newton studied with no particular distinction, though he was extremely skilful in making models, intricate mechanical toys (игрушки), sunclocks and so on.

His first " tutor" in science and the man who impressed Isaac most by his great charm and popularity was Descartes, who died when Newton was eight years old. Descartes' powerful imagination had enabled him to write not only serious scientific papers but a great number of popular scientific books and even science-fiction novels. In his serious scientific papers Des­cartes was able to concentrate the most advanced scientific ideas of his time widely ranging from philosophy to many fields of exact sciences in­cluding physics. *In his fancy-novels the features of real and imaginable worlds were so fantastically interconnected that Isaac Newton was com­pletely carried away by this brilliant, charming, powerfully clever and so popular Frenchman in those years. Descartes' influence on Newton can be felt in all the latter's works and through all his life. As to scientific ideas it was much later, that Newton understood the weakness of Descartes' ap­proach to solution of specific problems.

Newton was personally an extremely odd (эксцентричный) character, very reserved and even secretive ['sikrativ]. He never married. *He knew

enough to make him very self-critical, but this made him even more resentful of the criticism of other people.

In 1684, Halley, Newton's friend, offered a prize for the solution of the celestial body motion problem. *Many men led up to it, but only one had the genius to find the answer to it. That genius was Isaac Newton who had attracted little notice of before that.

ЗАДАНИЯ К ТЕКСТУ

• Объясните, как вы понимаете выделенные в тексте слова.

• Переведите на русский язык предложения, помеченные в тексте звездочкой.

• Speak on the following topics:

1. The role Descartes played in Newton's life.

2. Newton as a scientist and a personality.

3. Newton didn't found his school. Why?

(4) Conversation Practice

• Answer the questions on Text 30A.

1. Why did historians divide the history of science into pre-Newtonian and post-Newtonian periods? 2. Who of the greatest pre-Newtonian period scientists could you name? 3. When was Newton's Principia published⁹ 4. What great scientific discoveries could you compare this work to? Why? 5. What did Newton want to demonstrate in his work? 6. How and by means of what method did he do it? 7. What was the immediate significance of his calculus? 8. What branches of physics were developed based on Newton's laws?

• Speak on the following topics:

1. The Ancients' conceptions of the world.

2. The first scientific ideas of the structure of the solar system.

3. The three Kepler's laws of the planets' motion.

4. Newton's Principia and its significance for physics.

5. The world: two-dimensional, three-dimensional and foui-dimensional.

for his help, it would have been extremely difficult to deal with such accurate measurements. 4. Hadn't this assumption been made, we wouldn't have derived these data from experiments alone. 5. Were it not for such discoveries, we would make no progress in this field of technology. 6. But for his demand, we would have agreed on these terms. 7. Were we to approximate the ideal conditions of stability, we would provide the solution of the problem. 8. Should we test the hypothesis in practice, we would get the results desired.

⇐ Предыдущая123456789Следующая ⇒

Поделиться:

Популярное:

1. E) Воспитание сознательного отношения, склонности к труду как основной жизненной потребности путем включения личности в активную трудовую деятельность.
2. I. Драма одаренного ребенка, или как становятся психотерапевтами.
3. I. Сравните параллельные тексты.
4. I. Философия как мировоззрение, основной круг проблем
5. I.1 Творчество как средство социализации и развития личности
6. II – Предопределение, избрание и свобода воли
7. Ii) Основополагающий текст: Еф. 1:3-14
8. II. Найдите фрагменты из британских или американских видеофильмов,
9. II. ТЕКСТЫ ДЛЯ РАБОТЫ НАД ГОЛОСОМ.
10. II.1 Досуг как средство творческой самореализации личности
11. III. Две воли и два действия
12. III. ЛОГИЧЕСКАЯ ПЕРСПЕКТИВА СВЯЗНОГО ТЕКСТА.