Mechanical Engineering (Core Fundamentals, Thermodynamics, Fluid Mechanics, Solid
Mechanics, Design, & Manufacturing)
1. Which thermodynamic property is defined as the measure of the average kinetic energy of
the molecules in a substance?
A) Pressure
B) Volume
C) Temperature
D) Entropy
Answer: C) Temperature is a measure of the average kinetic energy of the molecules or atoms in
a system. Higher temperature corresponds to higher average molecular motion.
2. In a thermodynamic cycle, what is the net work output equal to?
A) The heat added during the process
B) The difference between heat added and heat rejected
C) The change in internal energy
D) The change in enthalpy
Answer: B) For a complete cycle, the net work output equals the net heat input (Q_in - Q_out),
as the change in internal energy over a cycle is zero (First Law of Thermodynamics).
3. What is the efficiency of a Carnot heat engine operating between a hot reservoir at 500 K
and a cold reservoir at 300 K?
A) 60%
B) 40%
C) 50%
D) 30%
Answer: B) Carnot efficiency η = 1 - (T_c/T_h) = 1 - (300/500) = 1 - 0.6 = 0.4 or 40%.
4. In fluid mechanics, what is the difference between a Newtonian and a non-Newtonian
fluid?
A) Newtonian fluids are compressible; non-Newtonian are incompressible
B) Newtonian fluids have constant viscosity; non-Newtonian fluids have variable viscosity
C) Newtonian fluids are always liquids; non-Newtonian are always gases
D) There is no difference
Answer: B) Newtonian fluids have a constant viscosity independent of shear rate (e.g., water,
air). Non-Newtonian fluids have viscosity that changes with shear rate (e.g., ketchup, blood,
polymer melts).
5. What is the physical significance of the Reynolds number in pipe flow?
A) It indicates the density of the fluid
,B) It predicts whether the flow is laminar or turbulent
C) It measures the speed of sound in the fluid
D) It represents the pressure drop per unit length
Answer: B) Re = (ρVD)/μ. Re < 2300 typically indicates laminar flow, while Re > 4000 indicates
turbulent flow. It is the ratio of inertial to viscous forces.
6. What is the maximum shear stress in a solid circular shaft subjected to a torque T?
A) Tr/J
B) T/J
C) Tc/J
D) TL/GJ
Answer: A) The maximum shear stress occurs at the outer surface (r = R) and is given by τ_max
= TR/J, where J is the polar second moment of area and R is the radius.
7. In a typical stress-strain diagram for ductile steel, what occurs after the yield point?
A) Elastic deformation stops and plastic deformation begins
B) The material fractures immediately
C) The material returns to original shape upon load removal
D) Stress becomes proportional to strain
Answer: A) Beyond the yield point, plastic deformation occurs, meaning the material will not
return to its original shape when the load is removed.
8. Which theorem provides a method for calculating the deflection of a beam?
A) Bernoulli's Theorem
B) Castigliano's Theorem
C) Euler's Theorem
D) Pascal's Theorem
Answer: B) Castigliano's theorem (specifically the second theorem) states that the partial
derivative of strain energy with respect to a force gives the displacement in the direction of that
force, widely used for beam deflections.
9. What is the primary function of a heat exchanger?
A) To convert thermal energy into mechanical work
B) To transfer heat from one fluid to another without mixing them
C) To generate electricity from heat
D) To store thermal energy
Answer: B) A heat exchanger transfers thermal energy between two or more fluids at different
temperatures, with the fluids typically separated by a solid wall to prevent mixing.
, 10. In a Rankine cycle, what is the purpose of the condenser?
A) To increase the pressure of the steam
B) To condense the exhaust steam from the turbine into liquid water
C) To superheat the steam before entering the turbine
D) To pump water back into the boiler
Answer: B) The condenser removes heat from the steam exiting the turbine, condensing it back
to liquid water so it can be pumped back to the boiler, thus completing the cycle.
11. What is Poisson's ratio for a perfectly incompressible material?
A) 0.0
B) 0.3
C) 0.5
D) 1.0
Answer: C) For an incompressible material, volume remains constant under uniaxial stress;
Poisson's ratio is exactly 0.5 (e.g., rubber). For most metals, it is ~0.3.
12. In a Brayton cycle (gas turbine), where is the heat addition process typically modeled to
occur?
A) At constant pressure
B) At constant volume
C) At constant temperature
D) Adiabatically
Answer: A) The ideal Brayton cycle consists of isentropic compression (compressor), constant-
pressure heat addition (combustor), isentropic expansion (turbine), and constant-pressure heat
rejection.
13. What does the first law of thermodynamics for a closed system state?
A) Entropy of the system always increases
B) Energy can be neither created nor destroyed, only changed in form
C) Heat always flows from hot to cold
D) Pressure and temperature are directly proportional
Answer: B) The First Law is a statement of the conservation of energy. For a closed system, Q -
W = ΔU (change in internal energy). Heat and work are energy transfer mechanisms.
14. Which type of stress is induced in a bolt when it is tightened?
A) Shear stress
B) Bending stress
C) Tensile stress
D) Torsional stress
Mechanics, Design, & Manufacturing)
1. Which thermodynamic property is defined as the measure of the average kinetic energy of
the molecules in a substance?
A) Pressure
B) Volume
C) Temperature
D) Entropy
Answer: C) Temperature is a measure of the average kinetic energy of the molecules or atoms in
a system. Higher temperature corresponds to higher average molecular motion.
2. In a thermodynamic cycle, what is the net work output equal to?
A) The heat added during the process
B) The difference between heat added and heat rejected
C) The change in internal energy
D) The change in enthalpy
Answer: B) For a complete cycle, the net work output equals the net heat input (Q_in - Q_out),
as the change in internal energy over a cycle is zero (First Law of Thermodynamics).
3. What is the efficiency of a Carnot heat engine operating between a hot reservoir at 500 K
and a cold reservoir at 300 K?
A) 60%
B) 40%
C) 50%
D) 30%
Answer: B) Carnot efficiency η = 1 - (T_c/T_h) = 1 - (300/500) = 1 - 0.6 = 0.4 or 40%.
4. In fluid mechanics, what is the difference between a Newtonian and a non-Newtonian
fluid?
A) Newtonian fluids are compressible; non-Newtonian are incompressible
B) Newtonian fluids have constant viscosity; non-Newtonian fluids have variable viscosity
C) Newtonian fluids are always liquids; non-Newtonian are always gases
D) There is no difference
Answer: B) Newtonian fluids have a constant viscosity independent of shear rate (e.g., water,
air). Non-Newtonian fluids have viscosity that changes with shear rate (e.g., ketchup, blood,
polymer melts).
5. What is the physical significance of the Reynolds number in pipe flow?
A) It indicates the density of the fluid
,B) It predicts whether the flow is laminar or turbulent
C) It measures the speed of sound in the fluid
D) It represents the pressure drop per unit length
Answer: B) Re = (ρVD)/μ. Re < 2300 typically indicates laminar flow, while Re > 4000 indicates
turbulent flow. It is the ratio of inertial to viscous forces.
6. What is the maximum shear stress in a solid circular shaft subjected to a torque T?
A) Tr/J
B) T/J
C) Tc/J
D) TL/GJ
Answer: A) The maximum shear stress occurs at the outer surface (r = R) and is given by τ_max
= TR/J, where J is the polar second moment of area and R is the radius.
7. In a typical stress-strain diagram for ductile steel, what occurs after the yield point?
A) Elastic deformation stops and plastic deformation begins
B) The material fractures immediately
C) The material returns to original shape upon load removal
D) Stress becomes proportional to strain
Answer: A) Beyond the yield point, plastic deformation occurs, meaning the material will not
return to its original shape when the load is removed.
8. Which theorem provides a method for calculating the deflection of a beam?
A) Bernoulli's Theorem
B) Castigliano's Theorem
C) Euler's Theorem
D) Pascal's Theorem
Answer: B) Castigliano's theorem (specifically the second theorem) states that the partial
derivative of strain energy with respect to a force gives the displacement in the direction of that
force, widely used for beam deflections.
9. What is the primary function of a heat exchanger?
A) To convert thermal energy into mechanical work
B) To transfer heat from one fluid to another without mixing them
C) To generate electricity from heat
D) To store thermal energy
Answer: B) A heat exchanger transfers thermal energy between two or more fluids at different
temperatures, with the fluids typically separated by a solid wall to prevent mixing.
, 10. In a Rankine cycle, what is the purpose of the condenser?
A) To increase the pressure of the steam
B) To condense the exhaust steam from the turbine into liquid water
C) To superheat the steam before entering the turbine
D) To pump water back into the boiler
Answer: B) The condenser removes heat from the steam exiting the turbine, condensing it back
to liquid water so it can be pumped back to the boiler, thus completing the cycle.
11. What is Poisson's ratio for a perfectly incompressible material?
A) 0.0
B) 0.3
C) 0.5
D) 1.0
Answer: C) For an incompressible material, volume remains constant under uniaxial stress;
Poisson's ratio is exactly 0.5 (e.g., rubber). For most metals, it is ~0.3.
12. In a Brayton cycle (gas turbine), where is the heat addition process typically modeled to
occur?
A) At constant pressure
B) At constant volume
C) At constant temperature
D) Adiabatically
Answer: A) The ideal Brayton cycle consists of isentropic compression (compressor), constant-
pressure heat addition (combustor), isentropic expansion (turbine), and constant-pressure heat
rejection.
13. What does the first law of thermodynamics for a closed system state?
A) Entropy of the system always increases
B) Energy can be neither created nor destroyed, only changed in form
C) Heat always flows from hot to cold
D) Pressure and temperature are directly proportional
Answer: B) The First Law is a statement of the conservation of energy. For a closed system, Q -
W = ΔU (change in internal energy). Heat and work are energy transfer mechanisms.
14. Which type of stress is induced in a bolt when it is tightened?
A) Shear stress
B) Bending stress
C) Tensile stress
D) Torsional stress
