40 fluid mechanics basic questions
📝 Fluid Mechanics – 40 One-Liner Q&A
Basics
1. Q: Define a fluid.
A: A fluid is a substance that deforms continuously under a small shear stress.
2. Q: Name the two types of fluids.
A: Liquids and gases.
3. Q: What is density?
A: Mass per unit volume ().
4. Q: What is specific gravity?
A: Ratio of density of a substance to the density of water.
5. Q: What is compressibility?
A: Ability of a fluid to change its volume under pressure.
6. Q: What is viscosity?
A: Resistance offered by a fluid to relative motion between layers.
7. Q: SI unit of viscosity?
A: Pascal-second (Pa·s).
8. Q: What is surface tension?
A: Force per unit length acting along the surface of a liquid.
9. Q: SI unit of surface tension?
A: Newton per meter (N/m).
10. Q: What is capillarity?
A: Rise or fall of liquid in a narrow tube due to surface tension.
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Fluid Types
11. Q: Define ideal fluid.
A: A fluid with zero viscosity and incompressibility.
12. Q: Define real fluid.
A: A fluid with viscosity and compressibility.
13. Q: Define Newtonian fluid.
A: A fluid with constant viscosity independent of shear rate.
14. Q: Example of Newtonian fluid.
A: Water, air.
15. Q: Define Non-Newtonian fluid.
A: A fluid whose viscosity changes with shear rate.
16. Q: Example of Non-Newtonian fluid.
A: Toothpaste, blood.
17. Q: What is incompressible fluid?
A: A fluid whose density remains constant under pressure.
18. Q: What is compressible fluid?
A: A fluid whose density changes with pressure.
19. Q: Example of compressible fluid.
A: Air, steam.
20. Q: Example of incompressible fluid assumption.
A: Water in hydraulic machines.
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Laws & Principles
21. Q: State Pascal’s law.
A: Pressure applied on a confined fluid is transmitted equally in all directions.
22. Q: State Archimedes’ principle.
A: A body immersed in a fluid experiences a buoyant force equal to the weight of displaced fluid.
23. Q: State Bernoulli’s theorem.
A: Total energy (pressure + kinetic + potential) remains constant along a streamline.
24. Q: State continuity equation.
A1V1=A2V2
25. Q: Define buoyancy.
A: Upward force exerted by a fluid on a submerged body.
26. Q: Condition for floating body?
A: Weight = Buoyant force.
27. Q: Condition for submerged body equilibrium?
A: Center of buoyancy and center of gravity must align.
28. Q: Define pressure.
A: Force per unit area.
29. Q: SI unit of pressure.
A: Pascal (Pa).
30. Q: Define manometer.
A: Device used to measure fluid pressure.
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Fluid Flow
31. Q: What is streamline flow?
A: Flow in which fluid particles move in parallel paths without mixing.
32. Q: What is turbulent flow?
A: Flow with irregular motion and mixing of fluid particles.
33. Q: Define Reynolds number.
A: Dimensionless number used to predict flow type.
34. Q: Critical Reynolds number for pipe flow?
A: Approximately 2000.
35. Q: Formula for Reynolds number?
A: .
36. Q: Define laminar flow.
A: Smooth and orderly flow of fluid (Re < 2000).
37. Q: Define turbulent flow.
A: Chaotic flow with eddies (Re > 4000).
38. Q: What is discharge?
A: Volume of fluid flowing per unit time ().
39. Q: SI unit of discharge?
A: m³/s.
40. Q: Define velocity potential.
A: A scalar function whose gradient gives fluid velocity in irrotational flow.
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