Essential vocabulary:

1. entity – сущность, объект

2. property - свойство

3. volume - объем

4. velocity - скорость

5. relevance - релевантность

6. density - плотность

7. to perceive - воспринимать

8. to cohere - слипаться

9. to settle down - устраиваться

10. solid – твердое вещество

11. drop - капля

12. jet - струя

13. surface - поверхность

14. beaker – химический стакан, колба

15. to constrain - ограничивать

16. to evaporate - испарять

17. to pick up - приобретать

18. to escape - исчезать

19. to exert - оказывать

20. a shear stress – свободное напряжение

21. to withstand - выдерживать

22. to yield – давать, уступать, сдаваться

23. to determine - устанавливать

24. viscosity – вязкость

25. friction - трение

26. adjacent - смежный

27. to slip over – выскальзывать, скользить

28. equilibrium - равновесие

29. plane - плоскость

30. irrespective - безотносительный

31. consistent - последовательный

32. equation - уравнение

I. Work in pairs. Discuss which sentence in b best continues the sentence in a:

A	B
1. The number of molecules per millilitre is	a) to move almost independently of one another.
2. In liquids the molecules are more or less in contact,	b) yield to shear stresses no matter how small these stresses may be.
3. In gases the molecules are sufficiently far apart	c) is normally long enough.
4. The lifetime of liquid drops and jets	d) that may exist in any solid or fluid medium.
5. There are two sorts of stress	e) so enormous that they need not be viewed as individual entities.
6. Fluids, by definition,	f) and the short-range attractive forces between them make them cohere.

II. Look at the groups of words below. Which word is the odd one?

1. a) fluid b) liquid c) solid d) pressure

2. a) molecules b) millilitre c) drops d) crystals

3. a) property b) velocity c) density d) volume

4. a) isotropic b) matter c) anisotropic d) macroscopic

5. a) substance b) pressure c) force d) stress

6. a) rate b) range c) perpendicular d) level

7. a) gravity b) orientation c) viscosity d) plane

III. Complete the sentences:

1. The vast … … … (including air and water) are isotropic.

2. Gases tend to … to fill any volume available to them.

3. The short-range attractive forces between molecules make them … .

4. The lifetime of liquid … and …, however, is normally long enough for evaporation to be ignored.

5. The shear stresses are everywhere zero in a … at rest and in … .

6. For an isotropic fluid in equilibrium there is only one value of the local … consistent with the stated values for ρ and T.

IV. Answer the following questions:

1. Why the molecules can’t be viewed as individual entities?

2. How the state of an isotropic fluid may be described in fluid mechanics?

3. How do the molecules usually act in gases?

4. How do the molecules move in liquids?

5. How the difference between two sorts of stress may be illustrated?