Words to be remembered:

gravity

friction

acceleration

contradict

conclusion

apparent

Inconsistency

velocity = speed

simultaneously

evacuate

сила тяжести

трение

ускорение

противоречить

заключение, вывод

видимый, явный

непоследовательность

скорость

одновременно

освобождать

№ 3

Physical quantities

The laws of physics are expressed in terms of the physical quantities. Among the physical quantities are force, time, ve­locity and density, temperature, charge and others. Many of these terms, such as force and temperature, are part of our everyday vocabulary.

Physical quantities are often divided into fundamental quantities and derived quantities. This division is arbitrary. A quantity can be regarded as fundamental in one set of opera­tions and as derived in another. Derived quantities are quantities which are defined in terms of other physical quantities. Examples of derived quantities are velocity, acceleration and volume. Fundamental quantities are not defined in terms of other physical quantities. The number of quantities regarded as fundamaental is the minimum number which is necessary in or­der to give a description of all the quantities of physics. Examples of fundamental quantities are length and time. Their definitions have two steps: first the choice of a standard, and second, establishment of procedures in order to compare the standard to the quantity which is necessary to measure.

An ideal standard has two principal characteristics: it is accessible and it is invariable. These two requirements are often incompatable and a compromise has to be found between them. The requirements of science and technology make invariability very directly connected with the human arm, foot, and thumb. Today such primitive measures of length are not satisfactory.

Words to be remembered:

in terms of

force

density

charge

quantity

vocabulary

derived

arbitrary

in order to

definition

procedure

accessible

invariable

incompatable

в терминологии, в единицах

сила

плотность

заряд

количество

словарь, запас слов

произведенный, выведенный

произвольный

для того, чтобы

определение

методика

доступный

неизменный

несовместимый

№4

MEASUREMENTS

In order to describe nature, the scientist needs a number of concepts which are so well defined that they are not merely descriptive ideas but are measurable quantities. The simplest of these are the ideas of size (length measurement) and duration (time measurement). Each property of an elementary particle - its mass, electric charge, energy, angular momentum - is such a quantitative concept.

The quantities which are discussed here are the basic vocabulary of physics. Unfortunately it is not possible to give precise definitions of all or even most of the fundamental concepts in physics at one time, and then build the theories of physics upon them. This happens simply because the concepts of physics cannot be separated from the laws of physics. Electric charge can be defined with quantitative precision only in connection with the law of electric force. Mass can be defined only in terms of certain mechanical measurements. Energy can be defined in its numerous forms only with the help of some knowledge of every great theory of physics. In spite of these limitations, it is important early in the study of physics to obtain what a physicist calls a “feeling” for the most important concepts, in order to be able to think meaningfully about the natural world.