NEET UG - Viscosity, Stokes law, terminal velocity, streamline and turbulent flow, critical velocity Online Test (MCQ Quiz)

1. Which of the following statements best defines viscosity?

A) The tendency of a fluid to resist compression. B) The property of a fluid that opposes relative motion between its layers. C) The pressure exerted by a fluid at rest. D) The rate at which a fluid flows through a narrow opening.

2. Viscosity is a measure of a fluid's internal resistance to:

A) Expansion B) Evaporation C) Flow D) Boiling

3. The SI unit of the coefficient of viscosity is:

A) Pascal-second (Pa·s) B) Poise (P) C) Stoke (St) D) Newton-second (N·s)

4. Which of the following is NOT a unit of viscosity?

A) Poise B) Pascal-second C) Dyne-second/cm² D) Newton/meter²

5. One Poise is equal to how many Pascal-seconds?

A) 0.01 B) 0.1 C) 1 D) 10

6. Stokes' Law describes the viscous force acting on a sphere moving through a fluid. What is the formula for this force?

A) F = 6πηrv B) F = 4πηrv C) F = 2πηrv D) F = 8πηrv

7. In Stokes' Law (F = 6πηrv), what does 'η' represent?

A) Radius of the sphere B) Velocity of the sphere C) Coefficient of viscosity of the fluid D) Density of the fluid

8. According to Stokes' Law, the viscous drag force on a sphere is directly proportional to:

A) Its radius squared B) Its velocity C) The square root of its radius D) The density of the fluid

9. Terminal velocity is reached when the net force acting on a falling object in a fluid is:

A) Maximum B) Zero C) Equal to the buoyant force D) Equal to the gravitational force

10. When an object falls through a viscous fluid and reaches terminal velocity, its acceleration is:

A) Maximum B) Minimum C) Zero D) Constant and non-zero

11. The terminal velocity of a sphere falling in a viscous fluid is directly proportional to:

A) The square of its radius B) The square root of its radius C) Its radius D) The viscosity of the fluid

12. If the radius of a sphere is doubled, its terminal velocity in a given viscous fluid will increase by a factor of:

A) 2 B) 4 C) 8 D) 16

13. Streamline flow is characterized by:

A) Chaotic and irregular fluid motion. B) Fluid particles moving in random paths. C) Smooth, orderly fluid motion where layers slide past each other. D) Rapid changes in fluid velocity and direction.

14. In streamline flow, the velocity of any fluid particle is:

A) Always constant B) Always changing randomly C) Constant at any given point in space D) Zero

15. Turbulent flow is characterized by:

A) Smooth, layered motion. B) Predictable fluid particle paths. C) Irregular, chaotic fluid motion with eddies and swirls. D) Low fluid velocities.

16. Which flow regime is associated with higher velocities and greater energy dissipation?

A) Streamline flow B) Laminar flow C) Turbulent flow D) Ideal flow

17. The Reynolds number (Re) is a dimensionless quantity used to predict the type of fluid flow. What does a low Reynolds number generally indicate?

A) Turbulent flow B) Streamline (laminar) flow C) Transitional flow D) Cavitation

18. A high Reynolds number typically indicates:

A) Streamline flow B) Laminar flow C) Turbulent flow D) Very low fluid viscosity

19. Critical velocity is the velocity above which a fluid flow transitions from:

A) Turbulent to streamline flow B) Streamline to turbulent flow C) Compressible to incompressible flow D) Steady to unsteady flow

20. For a given pipe and fluid, if the velocity exceeds the critical velocity, the flow regime is likely to become:

A) Streamline B) Laminar C) Turbulent D) Uniform

21. Which factor does NOT influence the critical velocity of a fluid in a pipe?

A) Diameter of the pipe B) Viscosity of the fluid C) Density of the fluid D) Temperature of the fluid

22. The formula for Reynolds number is given by Re = (ρvD)/η, where ρ is density, v is velocity, D is characteristic length, and η is dynamic viscosity. What does a higher value of ρ indicate for the Reynolds number, assuming other factors are constant?

A) Lower Reynolds number B) Higher Reynolds number C) No change in Reynolds number D) Reynolds number becomes zero

23. The relationship between the viscous force and velocity in streamline flow is:

A) Non-linear B) Quadratic C) Linear D) Exponential

24. If the viscosity of a fluid decreases, what happens to the terminal velocity of a sphere falling through it, assuming other factors remain constant?

A) Decreases B) Increases C) Remains the same D) Becomes zero

25. Poiseuille's law relates the flow rate of a viscous fluid through a pipe to pressure difference, viscosity, and pipe dimensions. The flow rate is inversely proportional to:

A) Pressure difference B) Radius of the pipe C) Length of the pipe D) Viscosity of the fluid

26. Which of the following is a characteristic of turbulent flow?

A) Conservation of energy is easily maintained. B) Viscous dissipation is minimal. C) Formation of eddies and vortices. D) Predictable particle trajectories.

27. The coefficient of viscosity of gases generally increases with:

A) Pressure B) Temperature C) Density D) Volume

28. The coefficient of viscosity of liquids generally decreases with:

A) Pressure B) Temperature C) Density D) Volume

29. When a sphere falls in a fluid, the forces acting on it are gravity, buoyancy, and viscous drag. At terminal velocity, which of the following is true?

A) Gravitational force = Buoyant force B) Gravitational force = Viscous drag force C) Buoyant force + Viscous drag force = Gravitational force D) Buoyant force = Viscous drag force

30. The unit of kinematic viscosity is:

A) m²/s B) Pa·s C) N·s/m² D) kg/(m·s)

31. Kinematic viscosity is defined as the ratio of dynamic viscosity to:

A) Pressure B) Temperature C) Density D) Velocity

32. If the density of a fluid increases, its kinematic viscosity will:

A) Increase B) Decrease C) Remain unchanged D) Become zero

33. Which phenomenon is directly related to the viscosity of the fluid through which an object moves?

A) Surface tension B) Capillary action C) Viscous drag D) Refraction

34. The flow of blood in our arteries is typically:

A) Turbulent B) Streamline C) Irregular D) Constant

35. Which of the following is a direct consequence of turbulent flow?

A) Reduced energy loss B) Increased efficiency of transport C) Increased resistance and energy dissipation D) Smoother flow through pipes

36. The critical velocity for flow through a pipe is generally lower for:

A) Higher viscosity fluids B) Lower viscosity fluids C) Denser fluids D) Wider pipes

37. Stokes' Law is applicable for the motion of:

A) Large objects in gases B) Small spherical objects in viscous liquids C) Objects in vacuum D) Objects moving at supersonic speeds

38. If the velocity of a fluid in a pipe is increased beyond the critical velocity, the flow pattern changes from laminar to:

A) Uniform B) Steady C) Turbulent D) Isothermal

39. The terminal velocity of a sphere falling in a viscous fluid is independent of:

A) Radius of the sphere B) Density of the sphere C) Viscosity of the fluid D) Acceleration due to gravity

40. Which property of a fluid determines the magnitude of the force resisting the relative motion of adjacent layers?

A) Density B) Surface tension C) Viscosity D) Compressibility

41. A fluid is flowing through a pipe. If the flow is streamline, the velocity at any point in the fluid remains:

A) Constant throughout the flow B) Variable with time C) Constant over time D) Zero

42. In the equation for terminal velocity (v_t = 2r²(ρ-σ)g / 9η), what does 'σ' represent?

A) Density of the sphere B) Density of the fluid C) Viscosity of the fluid D) Radius of the sphere

43. The transition from laminar to turbulent flow is influenced by the shape of the object and the:

A) Surface tension of the fluid B) Compressibility of the fluid C) Viscosity and density of the fluid D) Specific heat capacity of the fluid

44. Which of the following conditions would lead to a higher critical velocity for fluid flow in a pipe?

A) Increased viscosity B) Decreased density C) Increased pipe diameter D) Decreased viscosity

45. Stokes' Law is derived based on the assumption that the object is:

A) A cube B) A flat plate C) Spherical and moving slowly D) Moving at high speed

46. When a fluid flows from a wide section of a pipe to a narrow section at constant volume flow rate, its velocity:

A) Decreases B) Increases C) Remains constant D) Becomes zero

47. The resistance to flow in turbulent motion is generally:

A) Lower than in laminar flow B) Higher than in laminar flow C) Equal to laminar flow D) Dependent only on pressure

48. The unit of viscosity in the CGS system is:

A) Pascal-second B) Poise C) Stoke D) Dyne-second

49. If the density of the fluid and the radius of the sphere are kept constant, doubling the velocity of the sphere falling in a viscous fluid will:

A) Double the viscous drag force. B) Quadruple the viscous drag force. C) Halve the viscous drag force. D) Not change the viscous drag force.

50. Which of the following represents the correct relationship between streamline and turbulent flow?

A) Turbulent flow is always preferred for efficiency. B) Streamline flow occurs at lower velocities, and turbulent flow at higher velocities. C) Streamline flow is characterized by eddies and swirls. D) Turbulent flow is always predictable and smooth.

Viscosity, Stokes law, terminal velocity, streamline and turbulent flow, critical velocity - Online Test

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