2. Составьте словарь к тексту.

3. Прочитайте текст снова и письменно ответьте на вопросы:

1. Who defined the yard?

2. What is the fundamental unit of measurement on which all other units are based in the SI?

3. Why do many people not like the thought of changing over to metric units?

4. What system is more logical and much easier to use?

5. What country hasn't adopted the SI system as their national standard?

Вариант 2

1. Прочитайте и письменно переведите на русский язык текст:

UNITS OF MEASUREMENT

1. A unit of measurement is units of defined as a standard unit used to determine a particular quantitative characteristic. In metrology, there are different measurements for different characteristics (e.g., length, force, weight, speed, distance, etc.). Such units as length, mass, and time are called fundamental units. A fundamental unit can be quite arbitrary unit, for example, metre, second. All other units such as velocity, area, volume, density, temperature, and energy are called derived units. A derived unit is a combination of arbitrary unit, for example, kilogram per cubic metre. A system of units is that system of fundamental and derived units which enable us to express all quantities.

2. There are three main systems of fundamental units in use today; Metric, English, and SI (Systeme international d’unites).

3. The Metric System of Weights and Measures is based on the metre, kilogram, and second. Using metric system distance (length) is usually measured in millimetres, centimetres, metres, or kilometres; mass is measured in grammes or kilogrammes; and time is measured in seconds, minutes, or hours. The main advantage of the Metric System is that all metric units are divided into 10 or 100 parts. This enables fractional distances and masses to be expressed as decimals. Decimals are easier to manipulate in the addition, subtraction, multiplication, and division of two or more quantities.

4. The English System of Weights and Measures uses the foot, yard, and mile as units of length; the ounce, pound, and ton as units of force; and the second as the unit of time.

5. The SI System is a modification of the original metric system. The seven basic units in it are: metre (m), kilogram (kg), second (s), ampere (a), Kelvin (k), mole (mol), and candle (cd).

2. Составьте словарь к тексту.

3. Прочитайте текст снова и письменно ответьте на вопросы:

1. What is a unit of measurement?

2. What is a derived unit?

3. How many systems of fundamental units are there in use today?

4. What is the main advantage of the Metric System?

5. What does the English System of Weights and Measures use?

Вариант 3

1. Прочитайте и письменно переведите на русский язык текст:

THE ROLE OF STANDARDS

1. A standard is defined as a rule or a basis of comparison in measuring, quantity, weight, distance, value, or quality. Industry, commerce, international trade, and, in fact, modern civilization itself would be impossible without a good system of standards. The complex technological structure of modern civilization requires uniform, consistent, and repeatable measurements. The role of standards is to support such measurements.

2. Man has always converted the natural resources into devices and products to meet his needs and desires. He has always been concerned with the shape, size, proportions, and performances of the devices he has produced. In earlier times, parts of the human body were used to establish length, thickness, and height. The foot, for example, was used as a standard. At first, any human foot would do. Later, only the royal foot of a king or ruler was acceptable.

3. Today, the features and configurations of many devices are controlled to extremely close limits. All dimensions which affect the important characteristics such as size, shape, volume, and mass must be directly related to the same master standards.

4. To be useful, accurate, and efficient, standards must meet certain qualifications and requirements. The three main characteristics which standards must have are stability, reproducibility, and transferability. Mass, length, time, and temperature are the four standards basic to various measuring systems. All other physical quantities can be expressed in terms of these fundamentals. Temperature was based on a physical constant, but the other three basic standards were man-made standards. But man-made standards are not adequate for science and technology. Scientists, therefore, are gradually replacing man-made standards with standards based on physical constants. At present three of these standards length, time, and temperature are based on physical constants. Mass, a man-made constant, will probably remain for some time.