Principles and Practice of Engineering – Mechanical
Examination Questions And Correct Answers (Verified
Answers) Plus Rationales 2025/2026 Q&A | Instant
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1. A heat engine absorbs 500 kJ of heat from a high-temperature reservoir
and rejects 200 kJ to a low-temperature reservoir. What is the thermal
efficiency?
A) 20%
B) 40%
C) 60%
D) 80%
Rationale: Thermal efficiency, η = (Q_in – Q_out)/Q_in = (500 – 200)/500 = 0.6
or 60%.
2. For a steady, incompressible flow through a horizontal pipe, which term in
Bernoulli’s equation can be ignored?
A) Pressure
B) Elevation
C) Velocity
D) Viscous loss
Rationale: Horizontal flow implies no change in elevation; thus, the
gravitational potential energy term can be ignored.
3. Which of the following is a property of an ideal gas?
A) High viscosity
B) No intermolecular forces
C) Constant density
D) Non-compressible
Rationale: Ideal gases are assumed to have no intermolecular forces and follow
the ideal gas law.
,4. A 2 kg block moves on a frictionless surface under a 10 N force. What is its
acceleration?
A) 2 m/s²
B) 5 m/s²
C) 10 m/s²
D) 20 m/s²
Rationale: F = ma → a = F/m = 10/2 = 5 m/s².
5. In a counterflow heat exchanger, the temperature difference between
fluids is:
A) Constant
B) Zero
C) Maximum at one end, minimum at the other
D) Uniform
Rationale: Counterflow allows the largest temperature difference at one end
and smallest at the other, maximizing heat transfer.
6. Which process is isentropic?
A) Heat addition at constant pressure
B) Heat rejection at constant volume
C) Reversible adiabatic compression
D) Constant temperature expansion
Rationale: Isentropic = reversible adiabatic, no heat transfer and entropy
remains constant.
7. The Prandtl number (Pr) is the ratio of:
A) Viscous forces to inertial forces
B) Inertial forces to thermal diffusion
C) Momentum diffusivity to thermal diffusivity
D) Thermal diffusion to momentum diffusion
, Rationale: Pr = ν/α, where ν is kinematic viscosity and α is thermal diffusivity.
8. Which type of stress occurs due to twisting of a shaft?
A) Tensile
B) Compressive
C) Shear
D) Bending
Rationale: Torsion produces shear stress along the surface of the shaft.
9. A pump delivers 0.01 m³/s of water against a 50 m head. Assuming 100%
efficiency, the power required is (ρ = 1000 kg/m³, g = 9.81 m/s²)?
A) 4.9 kW
B) 5.0 kW
C) 4.905 kW
D) 50 kW
Rationale: P = ρgQH = 1000 × 9.81 × 0.01 × 50 = 4.905 kW.
10. Which of the following is a dimensionless number in fluid mechanics?
A) Reynolds
B) Friction factor
C) Froude
D) All of the above
Rationale: Reynolds, Froude, and Mach numbers are all dimensionless.
11. The primary function of a safety relief valve is to:
A) Regulate temperature
B) Maintain flow rate
C) Prevent overpressure
D) Minimize vibrations
Examination Questions And Correct Answers (Verified
Answers) Plus Rationales 2025/2026 Q&A | Instant
Download Pdf
1. A heat engine absorbs 500 kJ of heat from a high-temperature reservoir
and rejects 200 kJ to a low-temperature reservoir. What is the thermal
efficiency?
A) 20%
B) 40%
C) 60%
D) 80%
Rationale: Thermal efficiency, η = (Q_in – Q_out)/Q_in = (500 – 200)/500 = 0.6
or 60%.
2. For a steady, incompressible flow through a horizontal pipe, which term in
Bernoulli’s equation can be ignored?
A) Pressure
B) Elevation
C) Velocity
D) Viscous loss
Rationale: Horizontal flow implies no change in elevation; thus, the
gravitational potential energy term can be ignored.
3. Which of the following is a property of an ideal gas?
A) High viscosity
B) No intermolecular forces
C) Constant density
D) Non-compressible
Rationale: Ideal gases are assumed to have no intermolecular forces and follow
the ideal gas law.
,4. A 2 kg block moves on a frictionless surface under a 10 N force. What is its
acceleration?
A) 2 m/s²
B) 5 m/s²
C) 10 m/s²
D) 20 m/s²
Rationale: F = ma → a = F/m = 10/2 = 5 m/s².
5. In a counterflow heat exchanger, the temperature difference between
fluids is:
A) Constant
B) Zero
C) Maximum at one end, minimum at the other
D) Uniform
Rationale: Counterflow allows the largest temperature difference at one end
and smallest at the other, maximizing heat transfer.
6. Which process is isentropic?
A) Heat addition at constant pressure
B) Heat rejection at constant volume
C) Reversible adiabatic compression
D) Constant temperature expansion
Rationale: Isentropic = reversible adiabatic, no heat transfer and entropy
remains constant.
7. The Prandtl number (Pr) is the ratio of:
A) Viscous forces to inertial forces
B) Inertial forces to thermal diffusion
C) Momentum diffusivity to thermal diffusivity
D) Thermal diffusion to momentum diffusion
, Rationale: Pr = ν/α, where ν is kinematic viscosity and α is thermal diffusivity.
8. Which type of stress occurs due to twisting of a shaft?
A) Tensile
B) Compressive
C) Shear
D) Bending
Rationale: Torsion produces shear stress along the surface of the shaft.
9. A pump delivers 0.01 m³/s of water against a 50 m head. Assuming 100%
efficiency, the power required is (ρ = 1000 kg/m³, g = 9.81 m/s²)?
A) 4.9 kW
B) 5.0 kW
C) 4.905 kW
D) 50 kW
Rationale: P = ρgQH = 1000 × 9.81 × 0.01 × 50 = 4.905 kW.
10. Which of the following is a dimensionless number in fluid mechanics?
A) Reynolds
B) Friction factor
C) Froude
D) All of the above
Rationale: Reynolds, Froude, and Mach numbers are all dimensionless.
11. The primary function of a safety relief valve is to:
A) Regulate temperature
B) Maintain flow rate
C) Prevent overpressure
D) Minimize vibrations
