In gear nomenclature, what does the module represent?

The correct answer is B: Ratio of pitch circle diameter to number of teeth. Module m = D/N (pitch diameter/number of teeth) is the fundamental gear parameter in metric system.

For laminar flow between parallel plates, the velocity profile is parabolic. The average velocity is what fraction of the maximum velocity?

The correct answer is B: 0.50 times. For laminar flow between parallel plates, V_avg = V_max/2 = 0.5 × V_max. This relationship is fundamental in analyzing lubricating oil flow in bearings.

In journal bearing design, if the bearing length is doubled while keeping other parameters constant, how does the load capacity change?

The correct answer is A: Doubles. Load capacity in journal bearings is directly proportional to bearing length. Doubling the length doubles the total load-carrying area, thereby doubling the load capacity.

In open channel flow, the critical depth occurs when:

The correct answer is B: Froude number = 1. Critical depth in open channel flow corresponds to Fr = 1, minimum specific energy condition.

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Mechanical Engineering

Thermodynamics, hydraulics, machine design

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Topics in Mechanical Engineering

All Thermodynamics 100 Fluid Mechanics 79 Machine Design 80

Q.31 Easy Fluid Mechanics

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?

A 3.0 m/s

B 6.0 m/s

C 9.0 m/s

D 12.0 m/s

Correct Answer: B. 6.0 m/s

EXPLANATION

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

Test

Q.32 Easy Fluid Mechanics

Which of the following fluids is classified as non-Newtonian?

A Water

B Air

C Ketchup

D Mercury

Correct Answer: C. Ketchup

EXPLANATION

Ketchup is a pseudoplastic fluid whose viscosity changes with shear rate. Water, air, and mercury are Newtonian fluids with constant viscosity.

Test

Q.33 Easy Fluid Mechanics

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?

A 80 Pa

B 160 Pa

C 40 Pa

D 320 Pa

Correct Answer: A. 80 Pa

EXPLANATION

Shear stress τ = μ × (du/dy) = 0.8 × 100 = 80 Pa. This is a direct application of Newton's law of viscosity.

Test

Q.34 Easy Fluid Mechanics

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:

A 5 Pa

B 500 Pa

C 5000 Pa

D 0.002 Pa

Correct Answer: A. 5 Pa

EXPLANATION

τ = μ(du/dy) = 0.1 × 50 = 5 Pa

Test

Q.35 Easy Fluid Mechanics

For steady flow of an incompressible fluid through a variable area duct, which equation relates velocities at different sections?

A Bernoulli equation

B Continuity equation (A₁v₁ = A₂v₂)

C Energy equation

D Momentum equation

Correct Answer: B. Continuity equation (A₁v₁ = A₂v₂)

EXPLANATION

Continuity equation for incompressible flow states Q = constant, so A₁v₁ = A₂v₂

Test

Q.36 Easy Fluid Mechanics

For flow through an orifice, the discharge coefficient Cd is always:

A Greater than 1

B Equal to 1

C Less than 1

D Zero

Correct Answer: C. Less than 1

EXPLANATION

Cd < 1 accounts for vena contracta and frictional losses in actual orifice flow compared to ideal flow.

Test

Q.37 Easy Fluid Mechanics

Which of the following statements about boundary layers is correct?

A Boundary layer thickness increases linearly with distance

B Shear stress is zero at the wall surface

C Boundary layer develops due to viscous effects near the surface

D Boundary layer is independent of Reynolds number

Correct Answer: C. Boundary layer develops due to viscous effects near the surface

EXPLANATION

Boundary layer develops due to viscous effects that cause velocity gradient near solid surfaces, creating shear stress.

Test

Q.38 Easy Fluid Mechanics

For laminar flow in a circular pipe, the Hagen-Poiseuille equation gives volumetric flow rate as Q = πΔPd⁴/(128μL). This assumes:

A Turbulent flow with smooth pipes

B Incompressible, fully developed laminar flow

C Compressible flow with entrance effects

D Flow with variable viscosity

Correct Answer: B. Incompressible, fully developed laminar flow

EXPLANATION

Hagen-Poiseuille equation is valid for incompressible, fully developed laminar flow in circular pipes without entrance effects.

Test

Q.39 Easy Fluid Mechanics

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?

A 1.0 × 10⁻³ m²/s

B 6.4 × 10⁻⁴ m²/s

C 1.25 × 10⁻³ m²/s

D 8.0 × 10⁻⁴ m²/s

Correct Answer: A. 1.0 × 10⁻³ m²/s

EXPLANATION

Kinematic viscosity ν = μ/ρ = 0.8/800 = 1.0 × 10⁻³ m²/s

Test

Q.40 Easy Fluid Mechanics

In a converging nozzle, as the cross-sectional area decreases, the velocity of incompressible flow:

A Decreases

B Increases

C Remains constant

D First increases then decreases

Correct Answer: B. Increases

EXPLANATION

From continuity equation A₁V₁ = A₂V₂, when area decreases, velocity must increase to maintain constant mass flow rate.

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