A coupling is required for a motor-pump assembly where slight misalignment and vibration are expected. Which coupling type is MOST suitable?

The correct answer is B: Flexible coupling with elastomeric elements. Flexible couplings with elastomeric elements can accommodate angular, axial, and parallel misalignments while damping vibration, making them ideal for motor-pump assemblies with expected misalignment.

For a turbulent flow in pipes, the friction factor f in the Darcy-Weisbach equation depends primarily on:

The correct answer is B: Reynolds number and relative roughness. Friction factor for turbulent flow depends on Re and roughness (ε/d) as shown in Moody diagram.

For a Venturi tube with throat area ratio A₁/A₂ = 3 and upstream pressure P₁ = 200 kPa, assuming inviscid flow (Bernoulli applicable), if the pressure at throat P₂ drops to 80 kPa, the upstream velocity V₁ is (ρ = 1000 kg/m³):

The correct answer is C: 10.5 m/s. From Bernoulli: P₁/ρg + V₁²/2g = P₂/ρg + V₂²/2g. Using continuity A₁V₁ = A₂V₂, and solving: V₁ = √(2(P₁-P₂)/(ρ(A₂²/A₁²-1))) ≈ 10.5 m/s. Venturi tubes are standard in flow measurement systems.

A substance has a critical temperature Tc=647 K and critical pressure Pc=22.1 MPa. This is most likely:

The correct answer is B: Water. These are the critical constants for water. This falls within standard thermodynamic property tables for water.

In a constant volume process (isochoric), if temperature increases from 300 K to 600 K, the pressure ratio P₂/P₁ will be:

The correct answer is C: 2.0. For isochoric process: P/T = constant, so P₂/P₁ = T₂/T₁ = 600/300 = 2.0

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Mechanical Engineering
Thermodynamics

Thermodynamics, hydraulics, machine design

36 Q 3 Topics Take Mock Test

Difficulty: All Easy Medium Hard 31–36 of 36

Topics in Mechanical Engineering

All Thermodynamics 100 Fluid Mechanics 79 Machine Design 80

Q.31 Easy Thermodynamics

A heat engine operates between temperature reservoirs of 500 K and 300 K. What is the maximum possible efficiency of this engine?

A 40%

B 60%

C 50%

D 70%

Correct Answer: A. 40%

EXPLANATION

Maximum efficiency is Carnot efficiency = 1 - (T_cold/T_hot) = 1 - (300/500) = 0.4 = 40%

Test

Q.32 Easy Thermodynamics

Which process requires zero work to be done by the system?

A Isobaric process

B Isochoric process

C Isothermal process

D Adiabatic process

Correct Answer: B. Isochoric process

EXPLANATION

In an isochoric (constant volume) process, W = ∫PdV = 0 because volume does not change.

Test

Q.33 Easy Thermodynamics

The entropy of a reversible adiabatic process is:

A Increases

B Decreases

C Remains constant

D Becomes negative

Correct Answer: C. Remains constant

EXPLANATION

A reversible adiabatic process is also called isentropic, meaning entropy remains constant (ΔS = 0).

Test

Q.34 Easy Thermodynamics

For an ideal gas undergoing an isothermal process, the change in internal energy is:

A Maximum

B Zero

C Negative

D Positive

Correct Answer: B. Zero

EXPLANATION

In an isothermal process, temperature is constant. For an ideal gas, internal energy depends only on temperature, so ΔU = 0.

Test

Q.35 Easy Thermodynamics

The First Law of Thermodynamics is a statement of conservation of:

A Momentum

B Energy

C Entropy

D Enthalpy

Correct Answer: B. Energy

EXPLANATION

The First Law of Thermodynamics states that energy cannot be created or destroyed, only converted from one form to another.

Test

Q.36 Easy Thermodynamics

Which of the following is an intensive property in thermodynamics?

A Temperature

B Mass

C Volume

D Weight

Correct Answer: A. Temperature

EXPLANATION

Temperature is an intensive property as it does not depend on the quantity of matter. Mass, volume, and weight are extensive properties.

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