Unit 15 Theme: Kinematics. Grammar: Grammar revision.

Objectives: By the end of this unit, students should be able to use active vocabulary of this theme in different forms of speech exercises.

Students should be better at solving kinematics problems.

Methodical instructions: This theme must be worked out during two lessons a week according to timetable.

Lexical material: Introduce and fix new vocabulary on theme “Kinematics”.

Grammar: Practice and revise grammar themes of previous 7 units.

Kinematics

Kinematics is the branch of physics which describes motion with respect to speed, time and distance, the nature of the particle or object whose motion is under study being not specified. So, in kinematics we concern ourselves primarily with three physical quantities: 1) the distance between two positions; 2) speed, i.e. how fast a continuous change positions takes place; 3) the time it takes to get from one position (point, location) to another. Kinematics is not concerned with either the mass of a moving particle or forces producing change of speed.

Motion is defined in physics as continuous change of position. We describe motion from one position to another in terms of the distance moved and the time it takes to go from one position to another. We describe speed as amount of change of position per unit time, the amount of position being measured in units of length (distance). Generally, the word “per” indicates division, the mathematical definition of speed being х=d/t – or in other words speed is the distance travelled per unit time. The speedometer reads instantaneous velocity of a car in mph (miles per hour).

Constant velocity. A car moving with constant velocity, the distance travelled is directly proportional to the time. For constant velocity х, S=х*t, where S is the distance covered in time t. We may study particular motions by analyzing their graphs. Fig. 1 is an example of a speed-time graph. It shows us values of speed plotted against (vs) values of time. Of the three quantities involved in any study of motion, the speed-time graph relates to two directly. The quantity not shown directly is distance (length). A speed-time graph showing that speed doesn’t change with time, it is a graph of motion at constant speed. If the speed varies from one time period to the next we say it is a graph of a variable or no uniform (noconstant) speed.

Average velocity. Suppose a car in making a 60-mi. trip travels at 20 mph for the first 30-mi. and at 60 mph for the last 30-mi. We are tempted to say that the average velocity defined would be (20+60)/2, or 40 mph. However, this would be wrong because of the convention that average velocity is defined with respect to time and not with respect to distance. If t1 is the time needed to make the first part of the trip (at the velocity х1) and t2 is the time for the second part then average velocity with respect to time is х=(х1t1+х2t2)/(t1+t2) the preceding being an example of what is called a weighted average. We can calculate the average velocity of the car finding t1 and t2 from the relation t=S/х, the result being t1=30 mi/20 mph=1.5 hr and t2=30 mi/60 mph=0.5 hr. Substituting these values into the above equation we obtain х=(20*1.5+60*0.5)/(1.5+0.5) mph.

We then see that the average velocity for this trip is 30 mph rather than 40 mph.

Topical vocabulary

1. motion движение

2. respect расположение, связь

3. particle частица

4. concern отношение

5. primarily в основном, главным образом

6. quantity количество, размер, долгота звука

7. speed скорость

8. division деление, разделение

9. unit единица

10. constant velocity постоянная скорость

11. particular motion движение частиц

12. substitute замена, заместитель

13. plotted нанесенный, вычерчиваемый

14. relate to иметь отношение

15. vary изменяться

16. average средний

17. tempted притягиваемый

18. preceding предшествующий

19. a weighted average среднее взвешенное

20. obtain получать

21. equation уравнение, равенство

Ex.1. Read the text and aanswer the questions.

1. What does kinematics study?

2. Is the nature of the object under study specified?

3. In what units of measurement does the speedometer read the velocity?

4. Does it read the instantaneous or average velocity?

5. What is the relation between distance travelled and time if a car is moving with constant velocity?

6. What type of motion do we call one-dimensional motion? 7. What is the formula for the constant (instantaneous) velocity?

Ex.2. Fill in the gaps with the words and expressions from the text.

1. Kinematics is the branch of physics which describes … with respect to …, time and …, the nature of the particle or object whose motion is under study being not specified.

2. In kinematics we concern ourselves primarily with …physical quantities.

3. Kinematics is not concerned with either the … of a moving particle or … producing change of speed.

4. Motion is defined in physics as … … of position.

5. We describe speed as amount of change of position … unit time.

6. The speedometer reads … velocity of a car in mph (miles per hour).

7. A car moving with … …, the distance travelled is directly … to the time.

8. If the speed varies from one time period to the next we say it is a graph of a … or nonuniform (noconstant) speed.

Ex.3. Ask questions using the question-words in brackets.

1. In the kinematics we study position, velocity and acceleration (in what field of physics).

2. The speedometer reads the instantaneous velocity of a car (what velocity).

3. A car moving with constant velocity, the distance travelled is directly proportional to the time (on what condition).

4. The graph shows us values of speed plotted against values of time (what values).

5. This equation will give the wrong answer for the “speedometer reading” unless a very small value of S is used (on what condition).

6. Until we come to compound motion the discussion will be restricted (how long).

7. We shall use the symbol t to stand for the time taken to travel the distance S (what symbol).

Ex.4. Translate the following sentences paying attention to:

with respect to – относительно чего-то, учитывая.

1. The information being given with respect to the new data, it must be made use of in our research.

2. We defined the volume, all the measurements having been done with respect to the instruction.

3. The research having been carried out with no respect to errors, we do not consider it accurate.

rather, adv – довольно, до некоторой степени; скорее

rather than – а не, вместо того, чтобы; скорее, чем.

4. These measurements require rather high accuracy.

5. The speedometer reads the instantaneous velocity of a car rather then the average one.

6. This plot is rather for an object moving with uniform velocity.

7. In this case the magnitude rather than the direction of the velocity may change.

no matter – независимо от того.

8. No matter how accurate the measuring device can be, repeated readings will not be the same. 9. No matter how long it takes, you should make the experiment at least three times.

10. You are to apply the mean value of the voltage no matter which device you use.

Ex.5. Form the verbs from the following nouns according to the model.

Model : distribution – to distribute.

Calculation, displacement, observation, movement, description, production, variation, substitution, equation.

Ex.6. Retell the text using the out line.

1) the definition of kinematics; 2) the three physical quantities considered in kinematics; 3) the definition of motion in physics; 4) explanation of a speed-time graph.

Ex.7.Listening

Follow the link: http://www.youtube.com/watch?v=MMIjt3EajM4 (Computation and the Future of Mathematics)

Grammar: Grammar revision

Do exercises p.313-314 ex.:19-21,p.321 ex.:32-33 (Raymond Murphy “English Grammar in Use” A self-study reference and practice book for intermediate students of English Third Edition. Cambridge)

БӨЖ тапсырмалар:

“Mechanical engineering as future professions” try to remember five things about mechanical engineering . page 1 (КривоноговаО.В.

Mechanical Engineering) Волгоград: ВолГУ, 2004 г.

Follow the link and pass the tests for grammar:

http://www.study.ru/test/