LESSON 6
Topic: “UNITS OF MEASUREMENT (continuation)” Lead-in List all physical quantities you know.
Main stage Reading practice pp. 53-54 Reading: “Units of Measurement (continuation)”.
UNITS OF MEASUREMENT (Continuation)
Mass, length, time, area, velocity, acceleration - all of these are physical quantities. Whenever we measure one of these we are finding its magnitude. To find a magnitude of a physical quantity we must measure it. The magnitude of any physical quantity is expressed as number times a unit of measure.
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 on one day to its noon position the next day must be constant and is called the mean solar day. The laws of physics say also that the period of oscillation of a vibrating slab of crystal in a crystal oscillator should remain constant if the temperature and other external conditions are kept constant. So an electronic crystal oscillator can be made into a very accurate clock. The same is true of the vibrational frequency of atoms in a molecule. In fact atomic clocks counting up these vibrations are the most accurate of all.
The basic unit of time used in both the English and the metric systems is the second, the latter being 1/60 x 1/60 x 1/24 = 1/86.400 of a mean solar day. That is why we divide the mean solar day into 86.400 equal parts to get the unit used to measure time, namely 1 second.
A concept such as time basing on the laws of physics, we cannot be sure that these laws are absolutely correct. For example, suppose the speed of light is slowly increasing with the time. This would then cause a change in some of our standards of length and time. So far there is no experimental evidence that any of the universal physical constants is changing with time, this does not rule out the possibility of a very slow change beyond the accuracy of present measurements. 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 cc (cubic centimeter) of water (at a specified temperature and pressure), this amount of mass-being called the gram. Thus the density of water is conveniently one gram per cubic centimeter. Jn the English system the unit of mass is the pound, one kilogram (10’ grams) being equal to 2.204 pounds of mass. We will use the abbreviations gm for gram, kg for kilogram and lb for pound. In physics the quantities such as force and energy are usually measured either In meters, kilograms, and seconds or in centimeters, grams and seconds, the former being called the MKS system of units and the latter the CGS system of unite). Both of these metric systems are referred to in scientific papers.
Comprehension
p. 55 ex. 7 Answer the questions:
1. What is the definition of time related to? 2. Under what condition does the period of oscillation of a vibrating slab of crystal remain constant? 3. What can this fact be used for? 4. What can an electronic crystal oscillator be made into? 5 What can you say about atomic clocks counting vibrational frequency of atoms in a molecule?
Translation
a) Translate the text “Units of Measurement (continuation)” into Ukrainian.
b) Ex.4 p.55
4. Translate some sentences, paying attention to «following» and «followed»:
1. The calculations following the experiment gave accurate results. 2. The lecture followed by the demonstration of experiments was a success. 3. The practical studies following the theoretical ones were of great use. 4. Following this new method they achieved good results. 5. 10§ is a number expressed by one followed by eight zeroes. 6. Experiments of many other scientists following Rutherford's research proved his predictions.
Vocabulary practice
1. Give nouns corresponding to the following verbs: to discover, to act. to solve, to express, to observe, to measure, to define, to move, to suppose, to explain, to equip, to equal. 2. Keep in mind the following suffixes of nouns: a)-or, -cr, -ion, -tion. -sion, -ment, -ance, -encc: movement, difference, production, development, resistance, observation, measurement, reference, abbreviation, reducer, conductor; b) Give the verbs corresponding to these nouns.
3. Fill in the blanks with «accurate» (adj.), «accurately» (adv.), «accuracy» (n.) in the sentences and ask questions about the missing parts of the sentences:
1. We usually measure physical quantities... 2. They received... results. 3. The ... of the measurements surprised us. 4. They will carry out the experiment with...
Speaking practice
1. Units of measurement – to speak on 2. Pole play: “Units of measurement”
Grammar practice Ex. 6 p.55 6. Translate into Ukrainian. Pay attention to the Absolute Participle Constructions
1. The data being accurate, you may rely on it. 2. The theory having been discussed, they could proceed to practice. 3. Radioactivity discovered, we made great progress in atomic physics. 4. The laboratory being provided with necessary instruments, they could earn out the work successfully. 5. We must find this article, the subject presented in it being closely connected with our work. 6. With kinematics studying motion, position, velocity and acceleration are related to this field of physics. 7. With the object accelerating Eq. l will give the wrong answer. 8. With an object moving in a fixed direction or along a straight line, we call this type of motion one-dimensional motion. 9. With a car moving with constant velocity, the distance travelled is directly proportional to the time.
Homework 1. Home-reading (5.0) 2. Inquiry letter - to write Materials and resources:
1. Петрова Л.С. Методичні вказівки до вивчення курсу „Англійська мова”. – К., 2005. – 83с.