Water Resources · MCQ practice Properties of Fluid MCQs – Part 3
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Part 3 of 6 Question 31 Easy
The SI unit of kinematic viscosity is:
A N-s/m² B m²/s C cm²/s D dyne-s/m²
Answer: B. m²/s
The SI unit of kinematic viscosity (ν = μ/ρ) is m²/s. Its CGS unit is stoke (cm²/s).
Question 32 Easy
The unit of dynamic viscosity of a fluid is:
A N.m²/s B N/s²/m C N.m/s D N.s/m²
Answer: D. N.s/m²
The SI unit of dynamic viscosity is N·s/m² (or Pa·s).
Question 33 Easy
A fluid which has shear stress, is proportional to the rate of shear strain is called:
A Non-Newtonian fluid B Ideal fluid C Ideal Plastic fluid D Real fluid
Answer: D. Real fluid
A fluid where shear stress is proportional to shear strain rate is a Newtonian fluid, which is a real fluid (since ideal fluids have zero viscosity).
Question 34 Easy
The Bulk modulus of a fluid is given by 25 GPa. What is the compressibility (Pa⁻¹) of that fluid?
A 4 × 10⁻⁹ B 4 × 10⁻¹¹ C 25 × 10⁻⁹ D 25 × 10⁻¹¹
Answer: B. 4 × 10⁻¹¹
Compressibility is the reciprocal of bulk modulus: β = 1 / K = 1 / (25 × 10⁹ Pa) = 4 × 10⁻¹¹ Pa⁻¹.
Question 35 Easy
On increasing the temperature of a liquid, the viscosity of the liquid:
A Decrease B Increase C First decrease and then increase D Remains same
Answer: A. Decrease
The viscosity of a liquid decreases with increasing temperature because thermal energy weakens the cohesive intermolecular bonds.
Question 36 Easy
Which of the following represents the unit of kinematic viscosity?
A cm²/s B dyne-sec/cm² C gm/cm-sec D gm/cm²-sec
Answer: A. cm²/s
cm²/s is the CGS unit of kinematic viscosity, also known as the stoke.
Question 37 Easy
Which of the following is measured in the poise?
A Dynamic viscosity B Kinematic viscosity C Velocity of flow D Discharge
Answer: A. Dynamic viscosity
Dynamic viscosity is measured in poise (dyne·s/cm²), where 1 poise = 0.1 Pa·s.
Question 38 Easy
Which of the following expression represents the CORRECT relationship between the compressibility (C) and bulk modulus (K) of the fluid?
A C = 1 / √K B C = √K C C = 1 / K D C = K^(3/2)
Answer: C. C = 1 / K
Compressibility C is defined as the reciprocal of the bulk modulus of elasticity K: C = 1 / K.
Question 39 Easy
In the isothermal condition, the isothermal bulk modulus of an ideal gas is equal to:
A gas constant B pressure C temperature D viscosity
Answer: B. pressure
For an isothermal process (PV = constant), the bulk modulus K = −V(dP/dV) equals the absolute pressure P.
Question 40 Easy
Surface tension for an ideal fluid is:
A depends on temperature B one C infinite D zero
Answer: D. zero
An ideal fluid is an imaginary frictionless fluid that is incompressible, non-viscous, and has zero surface tension.
Question 41 Easy
Which of the following is not true about density of the gases?
A Proportional to pressure B Inversely proportional to temperature C Inversely proportional to volume D Do not depend on temperature and pressure
Answer: D. Do not depend on temperature and pressure
The density of a gas depends directly on pressure and inversely on temperature (ρ = P / RT), so stating that it does not depend on them is false.
Question 42 Easy
On increasing temperature, the viscosity of gas:
A decreases B first increases and then rapidly decrease C increases D not affected by temperature
Answer: C. increases
As temperature increases, gas molecules move faster and collide more frequently, increasing molecular momentum transfer and viscosity.
Question 43 Easy
If the velocity gradient is given by θ and dynamic viscosity of the fluid is given by μ. What is the shear stress on the wall of the boundary layer in the direction of motion?
A μθ B μ − θ C μ/θ D μ
Answer: A. μθ
By Newton's law of viscosity, shear stress τ = μ(du/dy). With du/dy = θ, τ = μθ.
Question 44 Easy
In which of the following unit kinematic viscosity of fluid is measured?
A m/s B m/s² C dyne D stokes
Answer: D. stokes
Kinematic viscosity is measured in stokes (CGS unit = cm²/s, where 1 stoke = 10⁻⁴ m²/s).
Question 45 Easy
Calculate the kinematic viscosity (stoke) of the fluid, if the dynamic viscosity of fluid is 0.5 poise and specific gravity is 0.4?
A 0.95 B 1 C 1.25 D 1.5
Answer: C. 1.25
In CGS units, kinematic viscosity ν = μ / ρ = 0.5 poise / 0.4 g/cm³ = 1.25 stokes.
Part 3 of 6