In an Otto cycle, the compression ratio is 10 and γ = 1.4. Calculate the thermal efficiency.

The correct answer is B: 60.2%. Otto cycle efficiency = 1 - (1/r^(γ-1)) = 1 - (1/10^0.4) = 1 - (1/2.512) = 1 - 0.3981 = 0.602 ≈ 60.2%

A shaft is designed for a combined bending moment of 1000 Nm and a torque of 800 Nm. Using the maximum shear stress theory, the equivalent torque is approximately:

The correct answer is C: 1414 Nm. Using maximum shear stress theory: T_eq = √(M² + T²) = √(1000² + 800²) = √(1,640,000) ≈ 1280.62 Nm. For von Mises: T_eq = √(M² + 0.75T²) ≈ 1204 Nm. The closest option using MSST is C.

The Darcy friction factor for fully developed laminar flow in a pipe depends on:

The correct answer is B: Reynolds number only. For laminar flow, friction factor f = 64/Re is independent of surface roughness. Roughness effects become significant only in turbulent flow.

In a U-tube manometer with mercury, if one leg shows 50 mm height difference, the pressure difference is:

The correct answer is B: 50 × ρ_mercury × g Pa. ΔP = ρgh = ρ_mercury × 9.81 × 0.05 ≈ 50 × ρ_mercury × g Pa (approximately)

According to Bernoulli's equation, which energy form is neglected when the fluid flow is at constant elevation in a horizontal pipe?

The correct answer is B: Potential energy. 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.

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Mechanical Engineering
Fluid Mechanics

Thermodynamics, hydraulics, machine design

23 Q 3 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–23 of 23

Topics in Mechanical Engineering

All Thermodynamics 100 Fluid Mechanics 79 Machine Design 80

Q.21 Easy Fluid Mechanics

The continuity equation for incompressible flow states that:

A A₁V₁ = A₂V₂

B A₁V₁² = A₂V₂²

C A₁²V₁ = A₂²V₂

D V₁/A₁ = V₂/A₂

Correct Answer: A. A₁V₁ = A₂V₂

EXPLANATION

The continuity equation for incompressible flow is based on mass conservation: ρA₁V₁ = ρA₂V₂, which simplifies to A₁V₁ = A₂V₂ when density is constant.

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Q.22 Easy Fluid Mechanics

Which of the following statements about streamline flow is correct?

A Streamlines can intersect each other

B Streamlines are paths followed by fluid particles

C Streamlines form closed loops in steady flow

D Velocity is perpendicular to streamline

Correct Answer: B. Streamlines are paths followed by fluid particles

EXPLANATION

Streamlines represent the paths followed by individual fluid particles in steady flow. They cannot intersect, and velocity is always tangential to streamlines.

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Q.23 Easy Fluid Mechanics

The unit of kinematic viscosity in SI system is:

A m²/s

B N·s/m²

C kg/(m·s)

D Pa·s

Correct Answer: A. m²/s

EXPLANATION

Kinematic viscosity is the ratio of dynamic viscosity to density. Its SI unit is m²/s or Stoke (1 Stoke = 10⁻⁴ m²/s).

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