Unit 2 lesson 1 systems of measurement

Key terms: measurement, the Common (English) system, themetric (international) system, the MKS system, the CGS system, value, convert, unit of distance, metre, aver­age time, mean solar day, second, mass, gram, pound, kil­ogram, force, energy.

1. There are two main systems of measurement in use today: the English system of units (or as it is after called the Common system of units) and the metric system of units (the SI). Except for the United States and Great Britain nearly all the nations of the world use the metric system. Although the English system of units is still the official system in the US, American scientists use the metric system almost exclusively. The value of the met­ric aystem is that its various units possess simple and logical relationshi p among themselves, while in the Common system 1 mile is equal to 1760 yards; 1 yard is equal to 3 feet; 1 foot is equal to 12 inches. In the latter system converting one unit into another is a hard and monotonous job.

2. In the metric system the main unit of distance is the metre. Other units of distance are always obtained by multiplying the metre by 10 or some power of 10. Thanks to our system ofwriting this means that conversions of one unit to another with­in the metric system can be carried out by shifts of a decimal point.

3. Time is a physical concept and its definition is related to certain laws of physics. The laws of physics say that the aver­age time it takes for the sun to move from its noon position one day to its noon position the other day is'called the mean solar day. The basic unit of time used in both the English and the metric systems is the second. It is equal to l/60th of a minute x l/60th of an hour x l/24th of a day = l/86,400th of a mean solar day.

4. Being also a physical concept mass must be defined in terms of certain laws of physics. In the metric system the unit of mass was originally defined as the amount of mass contained in 1 cubic centimetre (cc) of water at a specified temperature and pressure. This amount of mass is called the gram. Thus the density of water is conveniently one gram per cubic centimetre. In the English system the unit of mass is the pound, one kilo­gram being equal to 2.204 pounds of mass. We shall use the abbreviations gm for gram, kg for kilogram and lb for pound.

5. In physics the quantities such as force and energy are usu­ally measured either in meters, kilograms and seconds, or in centimetres, grams and seconds. The former system is called the MKS system and the latter the CGS (the Gaussian) system. Both of these metric systems are used in scientific papers.

Exercise 1. Give the English equivalents from the text to the following words and words-combinations:

1. фізичне поняття 6. тиск

2. одиниця часу 7. плотність

3. дорівнювати 8. сила

4. крім, не враховуючи 9. енергія

5. кількість 10. наукові статті

Exercise 2. Find the synonyms to the following words in the text.

1. to perform (2) 4. different (1) 7. due to (2)

2. to deal with (3) 5. quantity (4) 8. have (1)

3. defined (4) 6. get (2). 9. basic (2)

10. mean (adj.) (3)

Exercise 3. Find the correspondence:

1. nearly 1. в межах, у рамках

2. although 2. обидві (системи)

3. still 3. завдяки

4. almost 4. такі, як

5. while 5. хоч

6. thanks to 6. в той час, коли

7. within 7. або…або…

8. such as 8. майже

9. either…or… 9. тільки

10. both (systems) 10. досі

Exercise 4. Define the abbreviations:

1 the SI; the USA ;cc; ft ; gr; kg; lb; yd ;m.; the MKS; the CGS system.

Exercise 5. Say if the statements are true or false:

1. The British and American scientists use primarily the Common System.

2. Basic units in two main systems of measurement are not the same, but the basic unit of time is the same in both systems.

3. The advantage of the metric system is its inner logic and order.

4. All conversions of one unit to another in the metric system are very simple operations.

5. Both the MKS and the CGS systems are in current use.

Exercise 6. Complete the sentences choosing the right variant:

1. In the metric system the main unit of distance is…

a). the kilometre

b). the metre

c). the centimetre

2. In the English System the unit of mass is…

a). the gram

b). the pound

c). the foot

3. The Common System is the official one in…

a). India and Persia

b). the USA and the UK

c). China and Japan

4. …possesses simple and logical relationship among its units.

a). the MKS system

b). the SI

c). the CGS system

5. Conversions of one unit to another within the metric system can be carried out by…

a). multiplying the unit by 10

b). shifting a decimal point

c). multiplying the unit by some power of 10

Exercise 7. Answer the following questions:

1. What are two main systems of measurement today? Where are they used?

2. Which one of mentioned above systems is more advantageous?

3. What is time as physical concept with its unit related to?

4. How is the unit of mass defined in the SI?

5. What units are the quantities such as force and energy measured in?

Exercise 8. Examine the usage of two main systems of measurement.

Exercise 9. Define the main units of distance, time, mass in both systems of measurement.

Exercise 10. Prove that metric system has more advantages than the Common one.

Exercise 11. Describe how all conversions of units within the metric system are performed.

Exercise 12. Explain why some physical concepts must be defined in terms of certain laws of physics.

Exercise 13. Discuss the text according to the points:

1. Two main systems of measurement.

2. The advantages of metric system.

3. The MKS system and the CGS system.

4. The main concepts and their units in the Common System and the SI.

Notes:

1. to possess relationship – мати стосунок

2. multiply – множити

3. shift – зсув, зміщення

4. a decimal point – десяткова кома

5. mean solar day – середня сонячна доба

6. exclusively – винятково

7. value – величина, значення

8. conversion – перетворювання

9. the former - перший

10. the latter - останній.