Bernoulli's equation is valid for inviscid (frictionless), incompressible, steady flow along a streamline. It represents energy conservation in such flows.
Q.42Easy
Water at 20°C flows through a pipe network. The dynamic viscosity of water at 20°C is approximately:
Answer: A
The dynamic viscosity of water at 20°C is approximately 1.002 × 10⁻³ N·s/m² or 0.001 N·s/m², which is used in Reynolds number calculations.
Q.43Easy
In a converging nozzle, as the cross-sectional area decreases, the velocity of incompressible flow:
Answer: B
From continuity equation A₁V₁ = A₂V₂, when area decreases, velocity must increase to maintain constant mass flow rate.
Q.44Easy
A fluid with dynamic viscosity μ = 0.8 Pa·s and density ρ = 800 kg/m³ flows through a pipe. What is the kinematic viscosity?
For laminar flow in a circular pipe, the Hagen-Poiseuille equation gives volumetric flow rate as Q = πΔPd⁴/(128μL). This assumes:
Answer: B
Hagen-Poiseuille equation is valid for incompressible, fully developed laminar flow in circular pipes without entrance effects.
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Q.46Easy
Which of the following statements about boundary layers is correct?
Answer: C
Boundary layer develops due to viscous effects that cause velocity gradient near solid surfaces, creating shear stress.
Q.47Easy
For flow through an orifice, the discharge coefficient Cd is always:
Answer: C
Cd < 1 accounts for vena contracta and frictional losses in actual orifice flow compared to ideal flow.
Q.48Easy
For steady flow of an incompressible fluid through a variable area duct, which equation relates velocities at different sections?
Answer: B
Continuity equation for incompressible flow states Q = constant, so A₁v₁ = A₂v₂
Q.49Easy
A fluid undergoes viscous deformation with velocity gradient du/dy = 50 s⁻¹. For Newtonian fluid with μ = 0.1 Pa·s, the shear stress is:
Answer: A
τ = μ(du/dy) = 0.1 × 50 = 5 Pa
Q.50Easy
A fluid with dynamic viscosity μ = 0.8 Pa·s flows between two parallel plates separated by 5 mm. If the velocity gradient is 100 s⁻¹, what is the shear stress in the fluid?
Answer: A
Shear stress τ = μ × (du/dy) = 0.8 × 100 = 80 Pa. This is a direct application of Newton's law of viscosity.
Q.51Easy
Which of the following fluids is classified as non-Newtonian?
Answer: C
Ketchup is a pseudoplastic fluid whose viscosity changes with shear rate. Water, air, and mercury are Newtonian fluids with constant viscosity.
Q.52Easy
A 300 mm diameter pipe reduces to 150 mm diameter. If velocity in the larger pipe is 1.5 m/s, what is the velocity in the smaller pipe, assuming incompressible flow?
Answer: B
By continuity equation A₁V₁ = A₂V₂. Since diameter ratio is 2:1, area ratio is 4:1, so V₂ = 1.5 × 4 = 6.0 m/s
Q.53Easy
For laminar flow in a circular pipe, the Hagen-Poiseuille equation gives discharge as Q = πΔPd⁴/(128μL). This is valid for Reynolds number:
Answer: B
Hagen-Poiseuille equation applies only to laminar flow where Re < 2300. Beyond this critical value, flow becomes transitional or turbulent.
Q.54Easy
In a convergent nozzle, which property increases as the flow accelerates?
Answer: C
In a convergent nozzle, pressure decreases and velocity increases due to Bernoulli's principle. Temperature may decrease due to pressure drop.
Q.55Easy
In compressible flow, if Mach number M = 1.2, the flow is classified as:
Answer: C
Mach number classification: M < 1 (subsonic), M = 1 (sonic), 1 < M < 5 (supersonic), M > 5 (hypersonic). M = 1.2 is supersonic.
Q.56Easy
In fluid mechanics, which of the following statements about Pascal's law is correct?
Answer: A
Pascal's law states that pressure applied to a confined fluid is transmitted undiminished in all directions. This principle is fundamental to hydraulic systems used in Indian industries.
Q.57Easy
The continuity equation for incompressible flow states that A₁V₁ = A₂V₂. If water flows through a pipe that narrows from 100 mm to 50 mm diameter, the velocity ratio V₂/V₁ is:
Answer: C
Using continuity equation: A₁V₁ = A₂V₂. Area ratio = (D₁/D₂)² = (50100)² = 4. Therefore V₂/V₁ = 4:1. This is critical for pipe flow analysis in water supply systems.
Q.58Easy
According to Bernoulli's equation, which energy form is neglected when the fluid flow is at constant elevation in a horizontal pipe?
Answer: B
In Bernoulli's equation (P/ρg + V²/2g + Z = constant), when flow is in a horizontal pipe at constant elevation, Z (potential energy head) remains constant and can be neglected in differential form.
Q.59Easy
In centrifugal pump design, the impeller exit diameter D₂ and speed N (rpm) determine the peripheral velocity U₂ = πD₂N/60. For a pump with D₂ = 300 mm running at 1500 rpm, the peripheral velocity is:
Answer: A
U₂ = π × 0.3 × 601500 = 23.56 m/s. This velocity is critical in pump design as it affects the Euler's head and pump efficiency in Indian water supply and irrigation projects.
Q.60Easy
Which of the following is the primary function of a key in mechanical design?
Answer: A
A key is a mechanical element that prevents relative rotational motion between a shaft and a hub or pulley by transmitting torque.
