Words to be remembered:
a number of
concept
descriptive
measurable
size
duration
property
elementary particle
angular
precise
precision
In spite of
limitation
meaningful
ряд, несколько
понятие
описательный
измеримый
размер
продолжительность
свойство
элементарная частица
угловой
точный
точность
несмотря на
ограничение
значащий; многозначительно
№5
THE GEOMETRY OF VECTORS
There are two points of difference between vectors and numbers. The first difference is that vectors are essentially geometric, number are not. Numbers may be represented geometrically, either by points on a line, or by distances measured along the line, but they need not be. And even if they are, the line is arbitrary; its direction in physical space is without significance. A vector, on the other hand, has meaning only when its direction in space is specified. For a mathematician, this "space" of vector may be itself an abstraction, such as a space of many dimensions, but it is still basically geometrical. For the physicist, the space of most vectors is the ordinary three-dimensional space of classical physics, the space of human perception. The second difference between vectors and numbers is the fact that the vector has no sign. To call a vector positive or negative has no meaning. A number has magnitude and direction. Direction may be thought as the generalization of the idea of sign. Instead of two possibilities (plus and minus), there are infinitely many possibilities for direction. Of course a vector may be added or subtracted, and it may appear in an equation with a plus sign or a minus sign. Every vector, whether pointing north, south, west, east, up or down has (as it is said) a positive magnitude. The idea of direction replaces the idea of sign.
Words to be remembered:
point
direction
space
significance
meaning
specify
dimension
three-dimensional
sign
magnitude
add
subtract
equation
replace
пункт, точка
направление
пространство
важность, значение
значение
указывать
измерение
трехмерный
знак
величина
складывать, прибавлять
вычитать
уравнение
заменять
№6
FREELY FALLING BODIES
A real object can rotate as it moves. Also a body may vibrate as it moves, for example, a falling water drop. These complications can be avoided if we consider the motion of a very small body that is called a particle. Mathematically, a particle is treated as a point, an object without extent, so that rotational and vibrational considerations are not involved.
Actually, there is no such thing in nature as an object without extent. The concept of "particle" is very useful because real objects often behave to a very good approximation as if they were particles. A body need not be small in usual sense of the word in order to be treated as a particle. We can find out a great deal about the motion of the sun and planets without appreciable error if we threat these bodies as particles. Even if the body is too large in order to be considered a particle for a particular problem, we can always think of it as if it is made up of a large number of a particles.
The most common example of motion with nearly constant acceleration is the example of a body that falls toward the earth. In the absence of air resistance it is found out that all bodies, regardless of their size, weight, or composition, fall with the same acceleration at the same point of the earth's surface, and if the distance which is covered by them is not too large, the acceleration remains constant throughout the fall. This ideal motion, in which air assistance and the small change in acceleration with altitude are neglected, is called "free fall".
The acceleration of a freely falling body is called the acceleration due to gravity and is denoted by the symbol g. Near the earth's surface its magnitude is approximately 32 ft/sec2, or 980 cm/ sec2, and it is directed down toward the center of the earth.
Words to be remembered:
object
rotate
complication
motion
extent
consideration
actually
approximation
appreciable
error
treat
particular
resistance
regardless of
composition
surface
altitude
due to
предмет, объект
вращаться
осложнение
движение
протяженность, размер
соображение
действительно, на самом деле
приблизительный подсчет
заметный, ощутимый
ошибка
трактовать, относиться к
особый
сопротивление
независимо от
состав
поверхность
высота
благодаря, из-за
№7
WEIGHT AND MASS
In common language, “weight” and “mass” are often spoken of as though they were the same things, and a body may be spoken of as “heavy” or “massive” interchangeably: even physicist sometimes fall into a trap. However, consider what weight is. This weight of a body is the force with which it is attracted to the earth.
What will happen to the spring to Hook's law? A simple way to measure the weight of an object is to suspend it from a coiled spring. In accordance with Hook’s law the force by which the body is attracted to the earth will extend the spring, and the amount of the extension is proportional to the force. A weights-measuring device of this sort is a spring balance.
The mass of a body, on the other hand, is the quantity of inertia it possesses. By Newton’s second law m=f/a: it is a force divided by an acceleration. Weight, which is a force, must by the same law be a mass multiplied by an acceleration. In the case of weight, which is the force of earth's gravitational field upon a body, the acceleration is, naturally, that which is produced by the earth’s gravitational field.
Words to be remembered:
interchangeable
trap
consider
attract
suspend
extension
device
spring balance
multiply
взаимозаменяемый
ловушка
рассматривать
притягивать
подвешивать
удлинение
прибор, устройство
пружинные весы
умножать
№8
THE ROLE OF GRAVITY
Among the fundamental forces of nature, gravity is of special interest for several reasons. It is, first of all, the only truly universal force. It acts on every material thing from electron to galaxy, and, as we have learned in this century, it even acts on particles like photons and neutrinos or energy in the development and growth of mechanics. Newton, in his definitive formulation of mechanics, drew upon the studies of motion near the earth, influenced by local gravity, and of planetary motion far from the earth, influenced by the sun’s gravity. Since Newton’s time, motion governed by gravitational force has provided the strictest tests of mechanics, has served as stimulus for much of the mathematical elaboration of the theory of mechanics, has led to the discovery of distant new planets, and in own are of artificial satellites, has revealed new details of the shape and structure of the earth. Through the study of the orbit of Mercury came the first hint of an imperfection of Newtonian mechanics. Mercury’s refusal to follow precisely the laws of classical mechanics stands now as one of the experimental supports of new mechanics of einstein’s general relativity.
Words to be remembered:
gravity
reason
galaxy
growth
provide
strict
elaboration
discovery
distant
artificial satellite
imperfection
precisely
support
сила тяжести
причина
галактика
рост
обеспечивать
строгий
уточнение
открытие
далекий, отдаленный
искусственный спутник
несовершенство
точно
поддержка
№9
ELEMENTARY ATOMIC STRUCTURE
All matter is made up of tiny particles known as atoms. There are only about a hundred different kinds of atoms, and they combine with each other in different ways to form groups called molecules. All matter is composed of atoms or molecules and some knowledge of how atoms are made will give us valuable information about the behaviour of matter.
In 1911, Rutherford in England discovered that an atom has a tiny nucleus which is positively charged and contains nearly all the mass of the atom. Distributed about the nucleus and revolving about it in orbits are much less massive negatively charged particles called electrons.
In a normal atom, there are exactly as many negatively charged electrons as are needed to neutralize the positive charge of the nucleus, so that the atom as a whole is electrically neutral. This is of course also true of all normal material substances, which are composed of atoms. The outermost electrons are less strongly bound to the atom than the inner ones, and there are the ones that take part in chemical reactions between atoms and that are responsible for the accumulation of an electric charge on bodies.
Words to be remembered:
matter
tiny
combine
behavior
nucleus
charge
distribute
revolve
substance
outermost
bind/bound
inner
to be responsible for
accumulation
вещество, материя
крошечный
соединять/ся/
поведение
ядро
заряд; заряжать
распределять
вращаться
вещество
крайний
связывать
внутренний
отвечать за
накопление
№ 10
MAGNETS AND MAGNETIC FIELDS (I)
The ancient Chinese knew that pieces of certain natural iron ores, when suspended by a string, take a definite position with one end pointing approximately north and the other approximately south. It is clear from the behaviour of the magnetic compass of loadstones and other magnets, both natural and artificial.
We can use the magnetic field of the earth to magnetize steel rods if we hold them in the direction of the magnetic field of the earth and hitting them repeatedly with a hammer. The violent impacts shake the tiny particles of the rod and orient them, least partially, in the direction of the field. As a matter of fact, all steel objects possess a certain small degree of magnetization induced by the terrestrial magnetic field.
If we bring two magnetized steel rods close together, we find the ends pointed the same way during the magnetization process, to repel each other and if one of the rods is turned around, the ends of the rods attract one another.
This behaviour shows that a long piece of magnetized material – a steel bar, or a compass needle - shows its magnetic properties most strongly in regions near its ends, known as the poles of the magnet. It also shows that like poles, i.e. poles that point toward the same direction, repel each other and that unlike poles attract. It is interesting to notice that the magnetic pole of the earth located near its geographic north pole is actually its magnetic south pole, and vice versa.
Words to be remembered:
ore
suspend
string
point
approximately
loadstone
steel rod
violent
impact
at least
partially
terrestrial
repel
steel bar
needle
vice versa
руда
подвешивать
веревка
указывать
приблизительно
природный магнит
стальной стержень
сильный
удар, толчок
по крайней мере
частично, отчасти
земной
отталкивать
стальной брусок
игла
наоборот
№ 11
MAGNETS AND MAGNETIC FIELDS (II)
Magnetic materials are made of atomic particles that are themselves small magnets. In a piece of unmagnetized iron or steel, these particles point squally in all directions. When the iron or steel is strongly magnetized, all the atomic magnets are lined up in substantially the same direction. In soft iron the atomic magnets line up very readily when the iron is placed in a magnetic field. Since soft iron magnetize readily, it also readily losses its magnetism. When it is removed from the magnetic field, the atomic magnets are immediately again thrown into completely random alignment.
In hard steel, however, and to an even greater extent in certain special alloys, the atomic magnets, when they have been aligned, remain aligned until the steel is heated to high temperatures. Permanent magnets are thus made of such materials. Conversely, it requires a strong field to magnetize these materials. It is important to remember that, unlike positive and negative charges, magnetic poles must always occur in pairs, and that it is impossible to cut a north or south pole from a magnet and carry it away. If we cut a magnet into two pieces, we’ll get two smaller magnets, since a new pair of poles will originate at the broken ends. On the basis of the atomic magnetic picture it is plain to see why north and south poles cannot be separated if a magnet is broken in two.
Words to be remembered:
line up
readily
random
alignment
alloy
permanent
conversely
originate
выстраиваться
легко, без труда
случайный
выстраивание в ряд, ориентация
сплав
постоянный
наоборот
возникать, создавать