Английский - 2курс_3семестр_physics

4. Translate into English using the participles.

1)Артистка, рассказывающая детям сказки по радио, знаменита на всю страну.

2)Сказка, рассказанная няней, произвела на ребенка большое впечатление.

3)Рассказав ребенку сказку, она пожелала ему спокойной ночи.

4)Моя бабушка, рассказавшая мне эту сказку, живет в маленьком домике на берегу озера.

5)Ребенок всегда с интересом слушает сказки, рассказываемые няней.

6)Рассказывая детям сказки, она говорит разными голосами, имитируя героев сказок.

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UNIT 12

Home-reading

Johannes Kepler

Johannes Kepler is now chiefly remembered for discovering the three laws of planetary motion that bear his name published in 1609 and 1619). He also did important work in optics (1604, 1611), discovered two new regular polyhedral (1619), gave the first mathematical treatment of close packing of equal spheres (leading to an explanation of

the shape of the cells of a honeycomb, 1611), gave the first proof of how logarithms worked (1624), and devised a method of finding the volumes of solids of revolution that (with hindsight!) can be seen as contributing to the development of calculus (1615, 1616). Moreover, he calculated the most exact astronomical tables hitherto known, whose continued accuracy did much to establish the truth of heliocentric astronomy (Rudolphine Tables, Ulm, 1627).

A large quantity of Kepler's correspondence survived. Many of his letters are almost the equivalent of a scientific paper (there were as yet no scientific journals), and correspondents seem to have kept them because they were interesting. In consequence, we know rather a lot about Kepler's life, and indeed about his character.

Kepler was born in the small town of Weil der Stadt in Swabia and moved to nearby Leonberg with his parents in 1576. His father was a mercenary soldier and his mother the daughter of an innkeeper. Johannes was their first child. His father left home for the last time when Johannes was five, and is believed to have died in the war in the Netherlands. As a child, Kepler lived with his mother in his grandfather's inn. He tells us that he used to help by serving in the inn.

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One imagines customers were sometimes bemused by the child‘s unusual competence at arithmetic.

Kepler's early education was in a local school and then at a nearby seminary, from which, intending to be ordained, he went on to enrol at the

University of Tübingen, then (as now) a bastion of Lutheran orthodoxy.

Throughout his life, Kepler was a profoundly religious man. All his writings contain numerous references to God, and he saw his work as a fulfilment of his Christian duty to understand the works of God. Man being, as Kepler believed, made in the image of God, was clearly capable of understanding the Universe that He had created. Moreover, Kepler was convinced that God had made the Universe according to a mathematical plan (a belief found in the works of Plato and associated with Pythagoras). Since it was generally accepted at the time that mathematics provided a secure method of arriving at truths about the world (Euclid's common notions and postulates being regarded as actually true), we have here a strategy for understanding the Universe. Since some authors have given Kepler a name for irrationality, it is worth noting that this rather hopeful epistemology is very far indeed from the mystic's conviction that things can only be understood in an imprecise way that relies upon insights that are not subject to reason. Kepler does indeed repeatedly thank God for granting him insights, but the insights are presented as rational.

At this time, it was usual for all students at a university to attend courses on

―mathematics‖. In principle this included the four mathematical sciences: arithmetic, geometry, astronomy and music. It seems, however, that what was taught depended on the particular university. At Tübingen Kepler was taught astronomy by one of the leading astronomers of the day, Michael Mästlin (1550

- 1631). The astronomy of the curriculum was, of course, geocentric astronomy, that is the current version of the Ptolemaic system, in which all seven planets -

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Moon, Mercury, Venus, Sun, Mars, Jupiter and Saturn - moved round the Earth,

their positions against the fixed stars being calculated by combining circular

motions. This system was more or less in accord with current (Aristotelian)

notions of physics, though there were certain difficulties, such as whether one

might consider as ‗uniform‘ (and therefore acceptable as obviously eternal) a

circular motion that was not uniform about its own centre but about another

point (called an ‗equant‘). However, it seems that on the whole astronomers

(who saw themselves as ‗mathematicians‘) were content to carry on calculating

positions of planets and leave it to natural philosophers to worry about whether

the mathematical models corresponded to physical mechanisms. Kepler did not

take this attitude. His earliest published work (1596) proposes to consider the

actual paths of the planets, not the circles used to construct them.

Kepler‘s problems with this Protestant orthodoxy concerned the supposed relation between matter and ‗spirit‘ (a non-material entity) in the doctrine of the Eucharist. This ties up with Kepler‘s astronomy to the extent that he apparently found somewhat similar intellectual difficulties in explaining how ‗force‘ from the Sun could affect the planets. In his writings, Kepler is given to laying his opinions on the line - which is very convenient for historians. In real life, it seems likely that a similar tendency to openness led the authorities at Tübingen to entertain well-founded doubts about his religious orthodoxy. These may explain why Mästlin persuaded Kepler to abandon plans for ordination and instead take up a post teaching mathematics in Graz. Religious intolerance sharpened in the following years. Kepler was excommunicated in 1612. This caused him much pain, but despite his (by then) relatively high social standing, as Imperial Mathematician, he never succeeded in getting the ban lifted.

Kepler died in Regensburg, after a short illness. He was staying in the city

on his way to collect some money owing to him in connection with the

Rudolphine Tables. He was buried in the local church, but this was destroyed in

the course of the Thirty Years' War and nothing remains of the tomb.

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PROBLEM SOLVING

1. Roy has a mass of 60 kg. Laurie has a mass of 65 kg. They are 1.5 m apart.

(a)What is the magnitude of the gravitational force of the earth on Roy?

(b)What is the magnitude of Roy‘s gravitational force on the earth?

(c)What is the magnitude of the gravitational force between Laurie and the sun?

2.During a solar eclipse, the moon, earth and sun all lie on the same line, with the moon between the earth and sun. Define your coordinates so that the earth and moon lie at greater x values than the sun. For each force, give the correct sign as well as the magnitude. (a) What force is exerted on the moon by the sun?

(b) On the moon by the earth? (c) On the earth by the sun? (d) What total force is exerted on the sun? (e) On the moon? (f) On the earth?

3.Suppose that on a certain day there is a crescent moon, and you can tell by the

shape of the crescent that the earth, sun and moon form a triangle with a 135° interior angle at the moon‘s corner. What is the magnitude of the total gravitational force of the earth and the sun on the moon?

4. Ceres, the largest asteroid in our solar system, is a spherical body with a mass

6000 times less than the earth‘s, and a radius which is 13 times smaller. If an astronaut who weighs 400 N on earth is visiting the surface of Ceres, what is her weight?

5. Prove, based on Newton‘s laws of motion and Newton‘s law of gravity, that all falling objects have the same acceleration if they are dropped at the same location on the earth and if other forces such as friction are unimportant. Do not just say, ―g = 9.8 m/s2 – it‘s constant.‖ You are supposed to be proving that g should be the same number for all objects.

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6. Astronomers have detected a solar system consisting of three planets orbiting the star Upsilon Andromedae. The planets have been named b, c, and d. Planet b‘s average distance from the star is 0.059 A.U., and planet c‘s average distance is 0.83 A.U., where an astronomical unit or A.U. is defined as the distance from the Earth to the sun. For technical reasons, it is possible to determine the ratios of the planets‘ masses, but their masses cannot presently be determined in absolute units. Planet c‘s mass is 3.0 times that of planet b. Compare the star‘s average gravitational force on planet c with its average force on planet b.

7. Some communications satellites are in orbits called geosynchronous: the satellite takes one day to orbit the earth from west to east, so that as the earth spins, the satellite remains above the same point on the equator. What is such a satellite‘s altitude above the surface of the earth?

8. (a) A certain vile alien gangster lives on the surface of an asteroid, where his weight is 0.20 N. He decides he needs to lose weight without reducing his consumption of princesses, so he‘s going to move to a different asteroid where his weight will be 0.10 N. The real estate agent‘s database has asteroids listed by mass, however, not by surface gravity. Assuming that all asteroids are spherical and have the same density, how should the mass of his new asteroid compare with that of his old one?

(b) Jupiter‘s mass is 318 times the Earth‘s, and its gravity is about twice Earth‘s.

Is this consistent with the results of part a? If not, how do you explain the discrepancy?

9.Where would an object have to be located so that it would experience zero total gravitational force from the earth and moon?

10.The International Space Station orbits at an average altitude of about 370 km above sea level. Compute the value of g at that altitude.

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CHAPTER III. THERMODYNAMICS

UNIT 13

Pressure

Read and translate the text, be ready to discuss the given information.

When we heat an object, we speed up the mind-bogglingly complex random motion of its molecules. One method for training complexity is the conservation laws, since they tell that certain things must remain constant regardless of what process is going on. Indeed, the law of conservation of energy is also known as the first law of thermodynamics.

But conservation of energy by itself is not powerful enough to explain certain empirical facts about heat. A second way to sidestep the complexity of heat is to ignore heat‘s atomic nature and concentrate on quantities like temperature and pressure that tell us about system‘s properties as a whole. This approach is called macroscopic. Pressure and temperature were fairly well understood in the age of Newton and Galileo, hundreds of years before there was any firm evidence that atoms and molecules even existed.

We restrict ourselves to a discussion of pressure in fluids at rest and in equilibrium. In physics, the term ―fluid‖ is used to mean either a gas or a liquid. The important feature of a fluid can be demonstrated by comparing with a cube of jello on a plate. The jello is a solid. If you shake the plate from side to side, the jello will respond by shearing, i.e., by slanting its sides, but it will tend to spring back into its original shape. A solid can sustain shear forces, but a fluid cannot. A fluid does not resist a change in shape unless it involves a change in volume.

If you‘re at the bottom of a pool, you can‘t relieve the pain in your ears by turning your head. The water‘s force on your eardrum is always the same, and is

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always perpendicular to the surface where the eardrum contacts the water. If your ear is on the east side of your head, the water‘s force is to the west. If you keep your head in the same spot while turning around so your ear is on the north, the force will still be the same in magnitude, and it will change its direction so that it is still perpendicular to the eardrum: south. This shows that pressure has no direction in space, i.e., it is a scalar. The direction of the force is determined by the orientation of the surface on which the pressure acts, not by the pressure itself. A fluid flowing over a surface can also exert frictional forces, which are parallel to the surface, but the present discussion is restricted to fluids at rest.

Based on experimental results, it appears that the useful way to define pressure is as follows. The pressure of a fluid at a given point is defined as F ﬩/A where A is the area of a small surface inserted in the fluid at that point, and F﬩ is the component of the fluid's force on the surface which is perpendicular to the surface.

This is essentially how a pressure gauge works. The reason that the surface must be small is so that there will not be any significant different in pressure between one part of it and another part. The SI units of pressure are evidently N/m2, and this combination can be abbreviated as the pascal, 1 Pa=l N/m2. The pascal turns out to be an inconveniently small unit, so car tires, for example, have recommended pressures imprinted on them in units of kilopascals.

The pressure within a fluid in equilibrium can only depend on depth, due to gravity. If the pressure could vary from side to side, then a piece of the fluid in between would be subject to unequal forces from the parts of the fluid on its two sides. But fluids do not exhibit shear forces, so there would be on other force that could keep this piece of fluid from accelerating. This contradicts the assumption that the fluid was in equilibrium.

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Self-check

How does this proof (last paragraph) fail for solids?

True or false?

1)Conservation of energy by itself is powerful enough to explain empirical facts about heat.

2)The term ―fluid‖ is used to mean either a gas or a liquid.

3)The kilopascal turns out to be an inconveniently small unit, so car tires, for example, have recommended pressures imprinted on them in units of pascals.

4)The law of conservation of energy is also known as the second law of thermodynamics.

5)A solid can sustain shear forces, but a fluid cannot.

Answer the following questions.

1)What are the ways to sidestep the complexity of heat?

2)What does the term ―fluid‖ mean?

3)Can a solid and a fluid sustain shear forces?

4)Does pressure have no direction in space?

5)What are SI units of pressure?

6)What would happen with a piece of fluid in equilibrium if the pressure could vary from side to side?

Topic for reports.

1)The first law of thermodynamics.

2)The second law of thermodynamics.

3)Blaise Pascal.

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GRAMMAR

Review of Tenses

1. Put the verbs in brackets into the present indefinite or the present continuous.

- Excuse me. What time 1) …does the bus for Plymouth leave…? (the bus for

Plymouth/leave)

-It 2) … (leave) in half an hour. 3) … (you/go) to Plymouth too?

-Yes. I 4) … (visit) my granddaughter. She 5) … (live) there. And you?

-I 6) … (live) there too. I 7) … (do) a course at the college.

-What subject 8) … (you/study)?

-Tourism.

-That‘s interesting.

-I 9) … (come) here twice a week because I 10) … (work) in a hotel at the moment. It‘s work experience.

-Yes, I 11) … (think) that is very important. 12) … (you/like) the work?

-Yes, I 13) … (love) it. Ah, look! Here comes the bus!

2. Put the verbs in brackets into the past indefinite or the past continuous.

1)He …was watching… (watch) TV when the telephone …rang… (ring).

2)I … (clean) the house while he … (work) in the garden.

3)When we … (find) the cat it … (play) under the bed.

4)Joan … (have) a shower when the window cleaner … (come).

5)Grandma … (knit) while Grandpa … (smoke) his pipe.

6)When I … (arrive) home, Father … (paint) the front door.

7)Bob and Sally … (walk) when it … (start) to rain.

8)What … (you/talk) about when I … (come) in?

9)I … (read) my newspaper when they … (knock) on the door.

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