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Practice Exam
Question 1. In a closed thermodynamic system, which property does NOT change during a reversible adiabatic process? A) Pressure B) Temperature C) Entropy D) Volume Answer: C Explanation: Entropy remains constant in a reversible adiabatic (isentropic) process. Question 2. The specific heat ratio (k) for an ideal diatomic gas at room temperature is approximately: A) 1.33 B) 1.40 C) 1.67 D) 2. Answer: B Explanation: For diatomic gases k ≈ 1.4. Question 3. In the Rankine cycle, the component that adds the most entropy to the working fluid is: A) Boiler B) Turbine C) Condenser D) Pump Answer: A Explanation: Heat addition in the boiler is irreversible, increasing entropy. Question 4. The thermal efficiency of an ideal Otto cycle depends primarily on:
Practice Exam
A) Compression ratio B) Cut‑off ratio C) Turbine inlet temperature D) Condenser pressure Answer: A Explanation: Efficiency η = 1 – 1/r^(k‑1), where r is compression ratio. Question 5. In a vapor‑compression refrigeration cycle, the coefficient of performance (COP) is defined as: A) Qc/W B) Qh/W C) W/Qc D) Qh/Qc Answer: A Explanation: COP = refrigerating effect (Qc) divided by compressor work (W). Question 6. Which of the following fluids is most suitable for a high‑temperature Brayton cycle turbine inlet? A) Water B) R‑134a C) Air D) Ammonia Answer: C Explanation: Air remains stable at high temperatures and is commonly used in Brayton cycles. Question 7. The exergy destruction in a component is directly proportional to: A) Temperature difference B) Heat transfer rate C) Entropy generation D) Work output
Practice Exam
Question 11. The Reynolds number for flow in a pipe is defined as: A) ρVD/μ B) μVD/ρ C) ρV/μD D) μ/ρVD Answer: A Explanation: Re = (ρ V D)/μ. Question 12. In a fully developed laminar pipe flow, the friction factor f is: A) 64/Re B) 0.079/Re^0.25 C) 0.3164/Re^0.25 D) 0. Answer: A Explanation: For laminar flow, f = 64/Re. Question 13. The Moody chart is used to determine: A) Mach number B) Friction factor C) Reynolds number D) Nusselt number Answer: B Explanation: The Moody diagram provides friction factor as a function of Re and relative roughness. Question 14. The dimensionless number that characterizes compressibility effects in a flow is: A) Reynolds number B) Mach number C) Froude number D) Prandtl number Answer: B Explanation: Mach number = V/a indicates compressibility.
Practice Exam
Question 15. In external flow over a flat plate, the laminar boundary layer thickness δ at distance x is approximated by: A) 5x/√Re_x B) 0.37x/Re_x^0.2 C) x/Re_x D) 0.664x/√Re_x Answer: D Explanation: For laminar flow, δ ≈ 5.0x/√Re_x ≈ 0.664x/√Re_x (order‑of‑magnitude). Question 16. The drag coefficient of a streamlined airfoil at low angle of attack is typically: A) 0.01–0.05 B) 0.1–0.2 C) 0.5–0.7 D) >1. Answer: A Explanation: Streamlined bodies have very low Cd. Question 17. The affinity laws for a centrifugal pump state that flow Q is proportional to: A) N B) N^2 C) N^3 D) √N Answer: A Explanation: Q ∝ N (speed), H ∝ N^2, P ∝ N^3. Question 18. The specific speed of a pump is used to:
Practice Exam
Answer: A Explanation: θ = TL/(J G). Question 22. In a simply supported beam with a uniformly distributed load w, the maximum bending moment occurs at: A) Mid‑span B) Supports C) Quarter‑span D) At load application point Answer: A Explanation: For UDL, M_max = wL²/8 at the centre. Question 23. The shear stress distribution across a rectangular beam’s cross‑section is: A) Parabolic B) Linear C) Uniform D) Zero at neutral axis Answer: B Explanation: Shear stress varies linearly from zero at the neutral axis to a maximum at the outer fibers. Question 24. The moment of inertia of a solid circular section about its centroidal axis is: A) πd⁴/64 B) πd⁴/32 C) πd⁴/128 D) πd⁴/ Answer: A Explanation: I = π d⁴ /64.
Practice Exam
Question 25. Mohr’s circle is used to determine: A) Deflection B) Principal stresses C) Fatigue limit D) Vibration modes Answer: B Explanation: Mohr’s circle graphically yields principal stresses and max shear. Question 26. According to the Tresca criterion, yielding begins when: A) σ₁ – σ₃ = σ_y B) (σ₁²+σ₂²+σ₃²)/2 = σ_y² C) √[(σ₁‑σ₂)²+(σ₂‑σ₃)²+(σ₃‑σ₁)²]/√2 = σ_y D) σ_eq = σ_y Answer: A Explanation: Tresca states max shear stress = σ_y/2 → σ₁‑σ₃ = σ_y. Question 27. The von Mises equivalent stress for a plane stress state (σₓ, σ_y, τ_xy) is: A) √(σₓ²+σ_y²‑σₓσ_y+3τ_xy²) B) √(σₓ²+σ_y²+3τ_xy²) C) (σₓ+σ_y)/2 D) √[(σₓ‑σ_y)²+3τ_xy²] Answer: D Explanation: σ_eq = √[(σₓ‑σ_y)²+3τ_xy²]. Question 28. The endurance limit of a steel component is typically taken as: A) 0.2 σ_UTS B) 0.5 σ_UTS C) 0.7 σ_UTS D) 0.9 σ_UTS Answer: B
Practice Exam
A) Bearing life at a given load B) Maximum static load C) Lubrication film thickness D) Heat generation Answer: A Explanation: L₁₀ life = (C/P)³·10⁶ revolutions. Question 33. The most common failure mode of a helical spring under cyclic loading is: A) Buckling B) Yielding C) Fatigue D) Creep Answer: C Explanation: Repeated tension/compression leads to fatigue failure. Question 34. In the Fe‑C phase diagram, the eutectoid composition is approximately: A) 0.02 % C B) 0.77 % C C) 2.14 % C D) 4.3 % C Answer: B Explanation: Eutectoid point occurs at ~0.77 % carbon (pearlite formation). Question 35. Quenching a steel part from the austenite region typically produces: A) Martensite B) Pearlite C) Ferrite D) Bainite Answer: A Explanation: Rapid cooling transforms austenite to martensite.
Practice Exam
Question 36. The most effective method to prevent galvanic corrosion between two dissimilar metals is: A) Painting B) Cathodic protection C) Increasing temperature D) Using a lubricant Answer: B Explanation: Cathodic protection forces the more active metal to become the cathode. Question 37. In sand casting, the most common defect caused by insufficient venting is: A) Cold shut B) Porosity C) Misrun D) Shrinkage cavity Answer: B Explanation: Trapped gases create porosity. Question 38. The die‑casting process is best suited for: A) Large, low‑precision parts B) Small, high‑precision aluminum components C) High‑temperature steel parts D) Composite laminates Answer: B Explanation: Die‑casting produces accurate, thin‑walled aluminum parts. Question 39. During hot forging, the material’s flow stress is reduced primarily because of:
Practice Exam
Question 43. In a simple pendulum, the period is independent of: A) Length B) Gravity C) Amplitude (small angles) D) Mass Answer: D Explanation: For small angles, period T = 2π√(L/g) does not involve mass. Question 44. The natural frequency of a single‑degree‑of‑freedom (SDOF) mass‑spring system is: A) √(k/m) B) k/m C) √(m/k) D) k·m Answer: A Explanation: ω_n = √(k/m). Question 45. Critical damping in a SDOF system occurs when the damping ratio ζ equals: A) 0 B) 0.5 C) 1 D) 2 Answer: C Explanation: ζ = 1 defines critical damping. Question 46. In forced vibration, resonance occurs when the forcing frequency equals the system’s: A) Damping ratio B) Natural frequency C) Stiffness D) Mass
Practice Exam
Answer: B Explanation: Resonance is at ω = ω_n. Question 47. The transfer function of a first‑order lag system with gain K and time constant τ is: A) K/(τs+1) B) (τs+1)/K C) K·τs D) 1/(Kτs+1) Answer: A Explanation: G(s)=K/(τs+1). Question 48. In a closed‑loop control system, the steady‑state error for a unit step input is zero if the system has: A) No integrator B) One integrator C) Two integrators D) Pure proportional gain only Answer: B Explanation: Type‑1 system (one integrator) yields zero error for step input. Question 49. The Routh‑Hurwitz criterion is used to: A) Determine damping ratio B) Compute natural frequency C) Assess system stability D) Find steady‑state gain Answer: C Explanation: It provides a systematic check for poles in the left‑half plane.
Practice Exam
Explanation: For constant wall temperature, Nu = 3.66. Question 54. In natural convection, the Grashof number represents the ratio of: A) Inertial to viscous forces B) Buoyancy to viscous forces C) Thermal to momentum diffusivity D) Conductive to convective heat transfer Answer: B Explanation: Gr = gβΔTL³/ν² (buoyancy/viscous). Question 55. The Stefan‑Boltzmann law states that the total emissive power of a blackbody is proportional to: A) T B) T² C) T³ D) T⁴ Answer: D Explanation: E = σT⁴. Question 56. In a shell‑and‑tube heat exchanger, the overall heat transfer coefficient U is affected by: A) Fouling resistance B) Wall thickness C) Fluid flow arrangement D) All of the above Answer: D Explanation: U incorporates fouling, conduction through wall, and convection on both sides.
Practice Exam
Question 57. The LMTD method for heat exchanger analysis requires that the two fluids: A) Have equal heat capacity rates B) Flow counter‑currently C) Have constant specific heats D) Be incompressible Answer: B Explanation: LMTD is derived for counter‑current (or parallel) flow; counter‑current gives larger temperature difference. Question 58. The effectiveness‑NTU (ε‑NTU) method is advantageous because it does not require: A) Knowledge of inlet temperatures B) Knowledge of outlet temperatures C) Heat capacity rate ratio D) Both A and B Answer: D Explanation: ε‑NTU uses NTU and capacity ratio, avoiding explicit inlet/outlet temperatures. Question 59. The payback period for an investment is defined as: A) Time to recover initial cost B) Time to double the investment C) Time to reach break‑even cash flow D) Time to achieve desired ROI Answer: A Explanation: Payback period = years needed for cumulative cash flow = initial cost.
Practice Exam
A) Actual work / ideal work B) Ideal work / actual work C) Heat added / work output D) Work output / heat added Answer: A Explanation: η_is = (actual work)/(isentropic work). Question 64. In a gas power cycle, the mean effective pressure (MEP) is a measure of: A) Peak pressure B) Average pressure work per cycle C) Maximum temperature D) Compressor work Answer: B Explanation: MEP = (work per cycle)/(displacement volume). Question 65. The critical speed of a rotating shaft is the speed at which: A) Maximum torque occurs B) Resonance with first bending mode occurs C) Bearing wear is minimized D) Vibration amplitude is zero Answer: B Explanation: Critical speed = natural frequency of first bending mode expressed in rpm. Question 66. The Prandtl number (Pr) is the ratio of: A) Momentum diffusivity to thermal diffusivity B) Thermal diffusivity to momentum diffusivity C) Viscous force to inertial force D) Heat transfer coefficient to conductivity
Practice Exam
Answer: A Explanation: Pr = ν/α = (μc_p)/k. Question 67. In a thin‑walled pressure vessel, the hoop stress is: A) p r / t B) p r / (2t) C) 2p r / t D) p t / r Answer: A Explanation: σ_hoop = p·r/t. Question 68. The coefficient of thermal expansion for steel is approximately: A) 1×10⁻⁶ /K B) 12×10⁻⁶ /K C) 35×10⁻⁶ /K D) 70×10⁻⁶ /K Answer: B Explanation: α ≈ 12 μm/m·K for carbon steel. Question 69. In a spring‑mass‑damper system, the damping coefficient c that yields ζ = 0.2 is: A) 0.2·2√(km) B) 0.2·√(km) C) 0.2·k/m D) 0.2·m/k Answer: A Explanation: ζ = c/(2√(km)) → c = 2ζ√(km). Question 70. The most common method to measure strain in a structure is:
