III. Read the text and do the tasks following it.

There are many words of long standing which the scientist has been accustomed to use with a meaning that might or might not be the same as its customary one.

Sometimes he restricts the meaning of the word. The physicist adopted the word "current" when he described the changed properties of a wire connected to a voltaic battery as an electric current. In 1827, G. S. Ohm discovered the constancy of the relation between electromotive force and current and gave the ratio the name of "resistance."

Sometimes, a scientist will take an ordinary word and expand or widen its meaning, so that a single thing gives its name to a group or category.

"Salt," for example, is a material that is essential for human beings and animals, and has a long association with social history.

Its name appears in the English language in such a word—as "salary" meaning that the money one earns is meant, in the first turn, for buying what is most necessary for human existence.

The chemist, however, uses the word to denote a class of compounds, which he defines as the products of replacing the hydrogen of an acid, wholly or in part, by a metal or a metallic radicle. Common salt is a compound which comes only to a limited extent within the terms of this definition and only to this limited extent do these two salts mean the same thing.

Sometimes, a scientist will seize a word and force it to do work for which it has no qualifications. Such is the case of a family of related words — "force," "work," "power" and "weight."

In mechanics, force does not mean strength. It seems to say no more than that a force is a push or a pull, and since in physics all things must be measured it acquires, from Newton's Law of Motion, a quantitative sense which makes it the product of mass and acceleration. This, of course, is quite different from anything that the word "force" implies in everyday use.

A weight, one is surprised to learn, is not only the familiar block of metal with a ring on top, but a force. This is logical, because things fall under their own weight with an acceleration (due to gravity), so that the weight of a thing has to be the force with which the earth attracts it.

As to "work," the physicist has decided that a force works, or does work, only when it moves something. I may push and pull in vain at some immovable obstacle, and find that, nevertheless, mathematically I have done no work.

After this it is quite easy to accept the idea that power has come to mean the rate at which work is done; or that metals suffer from "fatigue" or that oils can be made "to crack."

Scientific words do not change their basic meanings in the course of centuries, as many ordinary words do. This singleness of meaning, this constancy in form and function, give to scientific words a character which distinguishes them from other words, but relates them to the symbols of mathematics.

IV. Comprehension Check.

1. Find the English equivalents for the following words and phrases: электрический ток, электродвижущая сила, усталость, расщеплять, вес, ускорение, ограничивать значение, сопротивление, класс соединений, определять (обозначать), количественное значение, неподвижное препятствие.

Read the text again to decide if the statements are true or false. Correct the false ones with the facts from the text.

1. Sometimes, a scientist uses an ordinary word to give its name to a group or category.

2. The word “salary” origins from the word “salt”.

3. In mechanics, force is used in the meaning of strength.

4. The weight of a thing is the force with which the earth attracts it.

5. Both scientific and ordinary words do not change their basic meanings in the course of centuries.

Make a plan to the text.