According to the theory of boundary layer flow, the boundary layer thickness δ grows along a flat plate as δ ∝ √(νx/V). This relationship is derived from:

The correct answer is C: Navier-Stokes equations with boundary layer approximations. The √x dependence comes from solving the Navier-Stokes equations with boundary layer approximations (Blasius solution). This is fundamental to aerodynamic design in Indian aircraft industries.

A rolling contact bearing has an equivalent dynamic load of 8 kN and a rating life of 10,000 hours at 1500 RPM. Which bearing parameter is most affected by speed and load combination?

The correct answer is B: L10 life in revolutions. The L10 life (in revolutions) is directly affected by both the equivalent dynamic load and speed according to the bearing life equation: L₁₀ = (C/P)³ × 10⁶

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?

The correct answer is B: 6.0 m/s. 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

A simple epicyclic gear train is used in an automobile differential. What is its primary function?

The correct answer is B: Allow different wheel speeds while distributing torque during straight-line motion. The differential uses an epicyclic gear arrangement to allow the drive wheels to rotate at different speeds during cornering while maintaining equal torque distribution during straight-line acceleration.

Which of the following is a characteristic of turbulent flow in pipes?

The correct answer is B: Velocity profile is highly skewed near the wall with rapid mixing. Turbulent flow exhibits random fluctuations, eddies, and rapid mixing. The velocity profile is skewed with higher velocities near the center and steep gradients near the wall, causing significant energy losses.

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Mechanical Engineering

Thermodynamics, hydraulics, machine design

54 Q 3 Topics Take Mock Test

Difficulty: All Easy Medium Hard 51–54 of 54

Topics in Mechanical Engineering

All Thermodynamics 100 Fluid Mechanics 79 Machine Design 80

Q.51 Hard Thermodynamics

In a turbojet engine operating on a Brayton cycle, if the pressure ratio r_p increases, the thermal efficiency:

A Decreases

B Remains constant

C Increases

D First increases then decreases

Correct Answer: C. Increases

EXPLANATION

For Brayton cycle: η = 1 - 1/r_p^((γ-1)/γ). As pressure ratio r_p increases, efficiency increases. This is why modern turbojets use high pressure ratios.

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Q.52 Hard Thermodynamics

For a system undergoing a reversible process from state 1 to state 2, which statement is true?

A ΔS_universe = 0

B ΔS_system > 0

C ΔS_surroundings > 0

D ΔS_system = 0

Correct Answer: A. ΔS_universe = 0

EXPLANATION

For a reversible process: ΔS_universe = ΔS_system + ΔS_surroundings = 0. The system's entropy can increase or decrease, but total entropy doesn't change.

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Q.53 Hard Thermodynamics

The Clausius-Clapeyron equation relates vapor pressure to:

A Temperature only

B Temperature and latent heat of vaporization

C Volume and pressure

D Entropy and enthalpy

Correct Answer: B. Temperature and latent heat of vaporization

EXPLANATION

Clausius-Clapeyron: dp/dT = L/(T·Δv), where L is latent heat of vaporization and relates pressure-temperature relationship at phase equilibrium.

Test

Q.54 Hard Thermodynamics

A Carnot refrigerator operates between T_H = 300 K and T_C = 250 K. Its coefficient of performance (COP) is:

A 5

B 6

C 7

D 4

Correct Answer: A. 5

EXPLANATION

For Carnot refrigerator: COP_ref = T_C/(T_H - T_C) = 250/(300-250) = 250/50 = 5.

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