Hydrostatics: Practise Exercise 122 Short-answer questions on hydrostatics

Practise Exercise 122 Short-answer questions on hydrostatics

1. Define pressure.

2. State the unit of pressure.

3. Define a fluid.

4. State the four basic factors governing the pressure in fluids.

5. Write down a formula for determining the pressure at any point in a fluid in symbols, defining each of the symbols and giving their units.

6. What is meant by atmospheric pressure?

7. State the approximate value of atmospheric pressure.

8. State what is meant by gauge pressure.

9. State what is meant by absolute pressure.

10. State the relationship between absolute, gauge and atmospheric pressures.

11. State Archimedes’ principle.

12. Name four pressure measuring devices.

13. Standard atmospheric pressure is 101325 Pa.

State this pressure in millibars.

14. Briefly describe how a barometer operates.

15. State the advantage of a Fortin barometer over a simple barometer.

16. What is the main disadvantage of a Fortin barometer?

17. Briefly describe an aneroid barometer.

18. What is a vacuum gauge?

19. Briefly describe the principle of operation of a U-tube manometer.

20. When would an inclined manometer be used in preference to a U-tube manometer?

21. Briefly describe the principle of operation of a Bourdon pressure gauge.

22. What is a ‘dead weight tester’?

23. What is a Pirani gauge?

24. What is a McLeod gauge used for?

25. What is buoyancy?

26. What does the abbreviation BM mean?

27. What does the abbreviation GM mean?

28. Define BM in terms of the second moment of area I of the water plane, and the dis- placed volume V of a vessel.

29. What is the primary purpose of a ship’s inclining experiment?

Practise Exercise 123 Multiple-choice questions on hydrostatics

1. A force of 50 N acts uniformly over and at right angles to a surface. When the area of the surface is 5 m2, the pressure on the area is:

(a) 250 Pa

(b) 10 Pa

(c) 45 Pa

(d) 55 Pa

2. Which of the following statements is false?

The pressure at a given depth in a fluid

(a) is equal in all directions

(b) is independent of the shape of the container

(c) acts at right angles to the surface containing the fluid

(d) depends on the area of the surface

3. A container holds water of density 1000 kg/m3. Taking the gravitational acceleration as 10 m/s2, the pressure at a depth of 100 mm is:

(a) 1 kPa

(b) 1 MPa

(c) 100 Pa

(d) 1 Pa

4. If the water in Question 3 is now replaced by a fluid having a density of 2000 kg/m3, the pressure at a depth of 100 mm is:

(a) 2 kPa

(b) 500 kPa

(c) 200 Pa

(d) 0.5 Pa

5. The gauge pressure of fluid in a pipe is 70 kPa and the atmospheric pressure is 100 kPa. The absolute pressure of the fluid in the pipe is:

(a) 7 MPa

(b) 30 kPa

(c) 170 kPa

(d) 10/7 kPa

6. A U-tube manometer contains mercury of density 13600 kg/m3. When the difference in the height of the mercury levels is 100 mm and taking the gravitational acceleration as 10 m/s2, the gauge pressure is:

(a) 13.6 Pa

(b) 13.6 MPa

(c) 13 710 Pa

(d) 13.6 kPa

7. The mercury in the U-tube of Question 6 is to be replaced by water of density 1000 kg/m3. The height of the tube to contain the water for the same gauge pressure is:

(a) (1/13.6) of the original height

(b) 13.6 times the original height

(c) 13.6 m more than the original height

(d) 13.6 m less than the original height

8. Which of the following devices does not measure pressure?

(a) barometer

(b) McLeod gauge

(c) thermocouple

(d) manometer

9. A pressure of 10 kPa is equivalent to:

(a) 10 millibars

(b) 1 bar

(c) 0.1 bar

(d) 0.1 millibars

10. A pressure of 1000 mbars is equivalent to:

(a) 0.1 kN/m2

(b) 10 kPa

(c) 1000 Pa

(d) 100 kN/m2

11. Which of the following statements is false?

(a) Barometers may be used for the measurement of altitude.

(b) Standard atmospheric pressure is the pressure due to the mass of the air above the ground.

c)The maximum pressure that a mercury manometer, using a 1 m length of glass tubing, is capable of measuring is in the order of 130 kPa.

(d) An inclined manometer is designed to measure higher values of pressure than the U-tube manometer.

In Questions 12 and 13 assume that atmospheric pressure is 1 bar.

12. A Bourdon pressure gauge indicates a pressure of 3 bars. The absolute pressure of the system being measured is:

(a) 1 bar

(b) 2 bars

(c) 3 bars

(d) 4 bars

13. In question 12, the gauge pressure is:

(a) 1 bar

(b) 2 bars

(c) 3 bars

(d) 4 bars

In Questions 14 to 18 select the most suitable pressure-indicating device from the following list:

(a) Mercury filled U-tube manometer

(b) Bourdon gauge

(c) McLeod gauge

(d) aneroid barometer

(e) Pirani gauge

(f) Fortin barometer

(g) water-filled inclined barometer

14. A robust device to measure high pressures in the range 0 – 30 MPa.

15. Calibration of a Pirani gauge.

16. Measurement of gas pressures comparable with atmospheric pressure.

17. To measure pressures of the order of 1 MPa.

18. Measurement of atmospheric pressure to a high degree of accuracy.

19. Figure 22.7(b), on page 252, shows a U-tube manometer connected to a gas under pressure. If atmospheric pressure is 76 cm of mercury and h1 is measured in centimetres then the gauge pressure (in cm of mercury) of the gas is:

(a) h1

(b) h1 + 76

(c) h1 – 76

(d) 76 – h1

20. In question 19 the absolute pressure of the gas (in cm of mercury) is:

(a) h1

(b) h1 + 76

(d) 76 – h1

21. Which of the following statements is true?

(a) Atmospheric pressure of 101.325 kN/m2 is equivalent to 101.325 millibars.

(b) An aneroid barometer is used as a stan- dard for calibration purposes.

(c) In engineering, ‘pressure’ is the force per unit area exerted by fluids.

(d) Water is normally used in a barometer to measure atmospheric pressure.

22. Which of the following statements is true for a ship floating in equilibrium?

(a) The weight is larger than the buoyancy.

(b) The weight is smaller than the buoyancy.

(c) The weight is equal to the buoyancy.

(d) The weight is independent of the buoyancy.

23. For a ship to be initially stable, the meta- centric height must be: