Idaho Mechanical Engineer
Examination Advanced 100-Question
Practice Exam 2026 | Questions &
Answers with Detailed Rationales |
Complete Exam Prep & Study Guide
1. A mechanical engineer is designing a pressure vessel subject to cyclic
internal pressure. Which failure mode is most directly associated with
repeated stress fluctuations below the material's static yield strength?
A. Creep
B. Buckling
C. Fatigue
D. Brittle fracture
Answer: C. Fatigue
Rationale: Fatigue failure results from repeated or fluctuating stresses and can
occur even when the maximum stress is below the material's yield strength.
2. For a thin-walled cylindrical pressure vessel, which expression most closely
represents the circumferential or hoop stress?
,A. σ = pr/t
B. σ = pr/(2t)
C. σ = 2pr/t
D. σ = pt/r
Answer: A. σ = pr/t
Rationale: For a thin-walled cylinder, hoop stress is approximately pr/t, while
longitudinal stress is pr/(2t).
3. A steel shaft transmits 150 kW at 1,800 rpm. Approximately what torque
must the shaft transmit?
A. 398 N·m
B. 796 N·m
C. 1,194 N·m
D. 2,388 N·m
Answer: B. 796 N·m
Rationale: Using T = 9550P/n with P in kW and n in rpm, T = 9550(150)/1800 ≈
796 N·m.
4. In a centrifugal pump, cavitation is most likely to occur when:
A. Discharge pressure is excessive
B. Fluid velocity is zero
C. Local pressure falls below the fluid vapor pressure
D. Pump efficiency exceeds 90%
Answer: C. Local pressure falls below the fluid vapor pressure
Rationale: Cavitation occurs when static pressure locally drops below vapor
pressure, causing vapor bubbles that subsequently collapse and may damage
the pump.
5. For incompressible steady flow through a pipe of constant diameter,
neglecting leakage, the continuity equation requires:
,A. Pressure to remain constant
B. Velocity to remain constant
C. Density to increase
D. Temperature to remain constant
Answer: B. Velocity to remain constant
Rationale: For steady incompressible flow with constant cross-sectional area,
continuity requires the average velocity to remain unchanged.
6. Which dimensionless number represents the ratio of inertial forces to
viscous forces in fluid flow?
A. Prandtl number
B. Reynolds number
C. Nusselt number
D. Mach number
Answer: B. Reynolds number
Rationale: Reynolds number, Re = ρVD/μ, compares inertial effects with viscous
effects and is commonly used to characterize laminar and turbulent flow.
7. Water flows through a pipe at a velocity of 3 m/s with a hydraulic diameter
of 0.05 m. If the kinematic viscosity is 1.0 × 10⁻⁶ m²/s, the Reynolds number
is approximately:
A. 1,500
B. 15,000
C. 150,000
D. 1,500,000
Answer: C. 150,000
Rationale: Re = VD/ν = (3)(0.05)/(1.0 × 10⁻⁶) = 150,000, indicating turbulent flow
in a typical circular pipe.
8. In a heat exchanger, the log-mean temperature difference is used because:
, A. Heat-transfer temperature difference is generally constant
B. Temperature difference varies along the exchanger
C. Fluid properties are always constant
D. Radiation dominates convection
Answer: B. Temperature difference varies along the exchanger
Rationale: The temperature difference between the hot and cold streams
changes along the exchanger, so the logarithmic mean provides an appropriate
effective temperature difference.
9. Increasing the Reynolds number in a turbulent pipe-flow system generally
tends to:
A. Eliminate friction losses
B. Increase the relative importance of inertial effects
C. Make viscosity zero
D. Guarantee laminar flow
Answer: B. Increase the relative importance of inertial effects
Rationale: Reynolds number increases as inertial effects become more
significant relative to viscous effects.
10.Which thermodynamic property is defined as the energy transferred across
a system boundary because of a temperature difference?
A. Work
B. Enthalpy
C. Heat
D. Entropy
Answer: C. Heat
Rationale: Heat is energy transferred across a system boundary solely because
of a temperature difference.
Examination Advanced 100-Question
Practice Exam 2026 | Questions &
Answers with Detailed Rationales |
Complete Exam Prep & Study Guide
1. A mechanical engineer is designing a pressure vessel subject to cyclic
internal pressure. Which failure mode is most directly associated with
repeated stress fluctuations below the material's static yield strength?
A. Creep
B. Buckling
C. Fatigue
D. Brittle fracture
Answer: C. Fatigue
Rationale: Fatigue failure results from repeated or fluctuating stresses and can
occur even when the maximum stress is below the material's yield strength.
2. For a thin-walled cylindrical pressure vessel, which expression most closely
represents the circumferential or hoop stress?
,A. σ = pr/t
B. σ = pr/(2t)
C. σ = 2pr/t
D. σ = pt/r
Answer: A. σ = pr/t
Rationale: For a thin-walled cylinder, hoop stress is approximately pr/t, while
longitudinal stress is pr/(2t).
3. A steel shaft transmits 150 kW at 1,800 rpm. Approximately what torque
must the shaft transmit?
A. 398 N·m
B. 796 N·m
C. 1,194 N·m
D. 2,388 N·m
Answer: B. 796 N·m
Rationale: Using T = 9550P/n with P in kW and n in rpm, T = 9550(150)/1800 ≈
796 N·m.
4. In a centrifugal pump, cavitation is most likely to occur when:
A. Discharge pressure is excessive
B. Fluid velocity is zero
C. Local pressure falls below the fluid vapor pressure
D. Pump efficiency exceeds 90%
Answer: C. Local pressure falls below the fluid vapor pressure
Rationale: Cavitation occurs when static pressure locally drops below vapor
pressure, causing vapor bubbles that subsequently collapse and may damage
the pump.
5. For incompressible steady flow through a pipe of constant diameter,
neglecting leakage, the continuity equation requires:
,A. Pressure to remain constant
B. Velocity to remain constant
C. Density to increase
D. Temperature to remain constant
Answer: B. Velocity to remain constant
Rationale: For steady incompressible flow with constant cross-sectional area,
continuity requires the average velocity to remain unchanged.
6. Which dimensionless number represents the ratio of inertial forces to
viscous forces in fluid flow?
A. Prandtl number
B. Reynolds number
C. Nusselt number
D. Mach number
Answer: B. Reynolds number
Rationale: Reynolds number, Re = ρVD/μ, compares inertial effects with viscous
effects and is commonly used to characterize laminar and turbulent flow.
7. Water flows through a pipe at a velocity of 3 m/s with a hydraulic diameter
of 0.05 m. If the kinematic viscosity is 1.0 × 10⁻⁶ m²/s, the Reynolds number
is approximately:
A. 1,500
B. 15,000
C. 150,000
D. 1,500,000
Answer: C. 150,000
Rationale: Re = VD/ν = (3)(0.05)/(1.0 × 10⁻⁶) = 150,000, indicating turbulent flow
in a typical circular pipe.
8. In a heat exchanger, the log-mean temperature difference is used because:
, A. Heat-transfer temperature difference is generally constant
B. Temperature difference varies along the exchanger
C. Fluid properties are always constant
D. Radiation dominates convection
Answer: B. Temperature difference varies along the exchanger
Rationale: The temperature difference between the hot and cold streams
changes along the exchanger, so the logarithmic mean provides an appropriate
effective temperature difference.
9. Increasing the Reynolds number in a turbulent pipe-flow system generally
tends to:
A. Eliminate friction losses
B. Increase the relative importance of inertial effects
C. Make viscosity zero
D. Guarantee laminar flow
Answer: B. Increase the relative importance of inertial effects
Rationale: Reynolds number increases as inertial effects become more
significant relative to viscous effects.
10.Which thermodynamic property is defined as the energy transferred across
a system boundary because of a temperature difference?
A. Work
B. Enthalpy
C. Heat
D. Entropy
Answer: C. Heat
Rationale: Heat is energy transferred across a system boundary solely because
of a temperature difference.
