Philippine Mechanical Engineering Licensure Examination (MELE) — Questions and Answers

Question 1: The critical depth in open channel flow is defined as the depth at which:

The hydraulic radius is minimized
Flow velocity equals the wave speed (Froude number = 1) (Correct answer)
The channel slope equals the friction slope
Energy losses are maximized

Correct answer: Flow velocity equals the wave speed (Froude number = 1)

Critical depth occurs when Fr = V/√(gy) = 1, meaning flow velocity equals the shallow-water wave speed.

Question 2: What quality of the cable causes it to have no resistance to bending while it is under its own weight?

Non-flexible property
Extensible property
Flexibility property (Correct answer)
Static property

Correct answer: Flexibility property

The flexibility property of a cable is its characteristic that allows it to bend freely without developing internal bending moments. This means that the cable offers no resistance to changes in its curvature. Consequently, the internal force within the cable is always purely tensile and acts tangentially to its curve, which is a fundamental assumption in cable analysis.

Question 3: Which of the following operations can be carried out using broaching?

Threading
Grinding
Spline cutting (Correct answer)
Increasing the size of the existing hole for a certain length

Correct answer: Spline cutting

Broaching is a preferred method of machining for producing straight through holes of varied shapes and section sizes, internal and external through slots or grooves, external surfaces of various shapes, teeth of internal and external splines, and small spur gears.

Question 4: The 'no-slip condition' in viscous fluid mechanics states that:

Pressure is continuous across a solid boundary
The fluid velocity at a solid wall equals the wall velocity (Correct answer)
Turbulent fluctuations vanish at the wall
Density is constant near the boundary layer

Correct answer: The fluid velocity at a solid wall equals the wall velocity

The no-slip condition requires that viscous fluid immediately adjacent to a solid surface moves at the same velocity as the surface.

Question 5: Which of the following is not a biomaterial?

Metals
Ceramics
Polymers
None of the mentioned (Correct answer)

Correct answer: None of the mentioned

Biomaterials are substances engineered to interact with biological systems for medical applications. Metals (like titanium alloys), polymers (like polyethylene), and ceramics (like alumina) are all extensively used as biomaterials due to their diverse properties, biocompatibility, and suitability for various medical devices and implants. Therefore, none of the listed options are excluded from being biomaterials.

Question 6: A centrifugal pump operating far to the right of its Best Efficiency Point (BEP) will likely experience:

Recirculation at the impeller inlet and cavitation (Correct answer)
Reduced bearing loads due to lower pressure forces
Increased efficiency and reduced NPSHR
Higher developed head with stable, quiet operation

Correct answer: Recirculation at the impeller inlet and cavitation

At flows much higher than BEP, NPSHA may become insufficient relative to the elevated NPSHR, causing cavitation; inlet recirculation also develops at very high flows.

Question 7: The slip in a reciprocating pump is defined as:

Pressure difference across suction and delivery valves
Speed difference between motor and pump shaft
Difference between theoretical and actual discharge expressed as a fraction of theoretical discharge (Correct answer)
Leakage flow past the piston rings per stroke

Correct answer: Difference between theoretical and actual discharge expressed as a fraction of theoretical discharge

Slip = (Q_theoretical − Q_actual) / Q_theoretical, representing losses due to leakage and valve timing; negative slip is possible if inertia effects increase actual discharge.

Question 8: In the Euler turbomachinery equation, the torque on the runner depends on:

Total kinetic energy of flow at the runner inlet alone
Change in the whirl (tangential) component of absolute velocity (Correct answer)
Change in fluid pressure between inlet and outlet
Change in the axial component of relative velocity

Correct answer: Change in the whirl (tangential) component of absolute velocity

Euler's equation states T = ρQ(r₁V_w1 − r₂V_w2); only the whirl (tangential) velocity components contribute to angular momentum change and thus torque.

Question 9: A steel component undergoes cyclic loading. The S-N curve shows an endurance limit at 10^7 cycles. This means:

The part must be replaced every 10^7 cycles
The part will fail after exactly 10^7 cycles
Below this stress amplitude, fatigue failure will not occur (Correct answer)
The material loses all strength at 10^7 cycles

Correct answer: Below this stress amplitude, fatigue failure will not occur

The endurance limit is the stress amplitude below which steel can theoretically withstand infinite fatigue cycles without failure.

Question 10: The Airy stress function approach in 2D elasticity ensures equilibrium automatically. The compatibility condition requires the Airy function φ to satisfy:

∇²φ = p/E
∂⁴φ/∂x⁴ = 0
∇²φ = 0
∇⁴φ = 0 (Correct answer)

Correct answer: ∇⁴φ = 0

The Airy stress function must satisfy the biharmonic equation ∇⁴φ = 0 in the absence of body forces to ensure strain compatibility.

Question 11: What is (mgz) capable of?

microscopic potential energy
macroscopic kinetic energy
microscopic kinetic energy
macroscopic potential energy (Correct answer)

Correct answer: macroscopic potential energy

The expression (m*g*z) represents the gravitational potential energy of an object with mass 'm' at a height 'z' in a gravitational field 'g'. This is a form of macroscopic potential energy because it relates to the position of an entire body or system within a force field, rather than the microscopic kinetic or potential energies of its individual particles.

Question 12: The Gibbs phase rule (F = C - P + 2) for a single-component system at a point on the saturation curve gives how many degrees of freedom?

0
1 (Correct answer)
3
2

Correct answer: 1

For a single component (C=1) with two phases (P=2): F = 1 - 2 + 2 = 1, meaning only one intensive variable can be specified independently.

Question 13: Which type of polarization in dielectrics has the slowest response to an alternating electric field?

Ionic polarization
Electronic polarization
Orientational (dipolar) polarization
Space charge polarization (Correct answer)

Correct answer: Space charge polarization

Space charge polarization involves migration of free charges to interfaces and has the lowest frequency response, occurring only at very low frequencies.

Question 14: The effectiveness of a heat exchanger (ε) is defined as:

Actual heat transfer / Maximum possible heat transfer (Correct answer)
Outlet temperature / Inlet temperature
Heat transferred / Total surface area
Actual heat transfer / LMTD

Correct answer: Actual heat transfer / Maximum possible heat transfer

Heat exchanger effectiveness ε = Q_actual / Q_max, comparing actual performance to the thermodynamic maximum limited by the minimum capacity rate fluid.

Question 15: Which one of the following does not represent a pure form of matter?

Element
Both Compound and Solution
Compound
Solution (Correct answer)

Correct answer: Solution

A pure form of matter refers to substances with a uniform and definite chemical composition and distinct properties, such as elements (e.g., gold) and compounds (e.g., water). A solution, however, is a homogeneous mixture of two or more substances where the components retain their individual chemical identities and can be present in varying proportions. Therefore, a solution is not a pure form of matter.

Question 16: In CAD assembly modeling, a 'mate' constraint between two flat faces makes them:

Perpendicular to each other
Parallel but offset at a distance
Coplanar and facing each other (Correct answer)
Tangent

Correct answer: Coplanar and facing each other

A mate constraint in CAD assembly aligns two faces coplanar and facing (opposing normal directions), simulating physical contact between parts.

Question 17: Which crystal defect involves an extra half-plane of atoms inserted into the crystal lattice?

Edge dislocation (Correct answer)
Vacancy
Interstitial defect
Schottky defect

Correct answer: Edge dislocation

An edge dislocation is characterized by an extra half-plane of atoms, creating a line defect that enables plastic deformation by slip.

Question 18: An isometric view is a type of:

Pictorial (axonometric) projection (Correct answer)
Orthographic projection
Perspective projection
Section view

Correct answer: Pictorial (axonometric) projection

Isometric projection is an axonometric (pictorial) drawing where all three axes are equally inclined to the projection plane at 30°, giving equal foreshortening.

Question 19: Which of the following laws governs the ECM process?

Coulomb’s law
Faraday’s law (Correct answer)
Law of definite proportions
Law of chemical combination

Correct answer: Faraday’s law

that metal can be removed from the anode and plated on the cathode via a process known as electroplating, in which the workpiece serves as the cathode and two electrodes are positioned in a bath containing a conducting liquid. ECM makes use of a workpiece as an anode by removing the material.

Question 20: A material has a fracture toughness KIc = 50 MPa√m and a yield strength of 500 MPa. What is the critical crack length for plane strain fracture?

~10 mm
~3.2 mm (Correct answer)
~6.4 mm
~1.0 mm

Correct answer: ~3.2 mm

Using a = (1/π)(KIc/σ)² = (1/π)(50/500)² ≈ 0.0032 m = 3.2 mm for a through crack with Y=1.

Question 21: For a type-1 feedback control system subjected to a unit ramp input r(t) = t, the steady-state error is:

1/Ka, where Ka is the acceleration error constant
Zero
Infinite
1/Kv, where Kv is the velocity error constant (Correct answer)

Correct answer: 1/Kv, where Kv is the velocity error constant

A type-1 system has one open-loop integrator, giving a finite velocity error constant Kv; the steady-state ramp error equals 1/Kv, which is nonzero but finite.

Question 22: The Pilling-Bedworth ratio (PBR) predicts oxidation resistance. A PBR value between 1 and 2 indicates:

The metal undergoes catastrophic oxidation
The oxide layer is porous and non-protective
No oxidation occurs
The oxide layer is protective and adherent (Correct answer)

Correct answer: The oxide layer is protective and adherent

A PBR between 1 and 2 means the oxide volume slightly exceeds the metal volume consumed, creating a continuous, protective barrier.

Question 23: Which of the following statements holds true if two forces are represented by two triangle sides in that order?

The resultant’s magnitude is greatest
The resultant of two forces is represented by the third side in reverse order (Correct answer)
The resultant’s magnitude is zero
The resultant of two forces is represented by the third side in the same sequence

Correct answer: The resultant of two forces is represented by the third side in reverse order

This question describes the Triangle Law of Vector Addition. If two forces are represented by two sides of a triangle taken in the same sequential order, their resultant is given by the third side. Crucially, the resultant vector must be drawn from the tail of the first vector to the head of the second vector, meaning it closes the triangle and is therefore taken in the reverse order relative to the other two sides.

Question 24: Axial flow reaction turbines of particular significance are .

Kaplan and Francis turbines
Propeller and Pelton turbines
Propeller and Kaplan turbines (Correct answer)
Propeller and Francis turbines

Correct answer: Propeller and Kaplan turbines

Propeller and Kaplan turbines are both classified as axial-flow reaction turbines, meaning water flows parallel to the axis of rotation through the runner. The Kaplan turbine is an advanced version of the propeller turbine, distinguished by its adjustable runner blades. This adjustability allows Kaplan turbines to maintain high efficiency over a broader range of flow rates and heads, making them particularly significant for variable load conditions.

Question 25: In laser beam machining (LBM), the parameter most directly controlling the depth of material removed per pulse is:

Assist gas pressure
Peak power density (irradiance) at the workpiece surface (Correct answer)
Beam diameter at the lens
Wavelength of the laser source

Correct answer: Peak power density (irradiance) at the workpiece surface

Peak power density (W/cm²) determines whether the threshold for ablation, melting, or vaporization is exceeded and how deeply each pulse penetrates the material.

Question 26: In GD&T, flatness tolerance controls:

Angle between two surfaces
Parallelism to a datum
How flat a surface is (with no datum reference) (Correct answer)
How flat a single surface is relative to a datum

Correct answer: How flat a surface is (with no datum reference)

Flatness in GD&T controls all points on a surface lying within two parallel planes separated by the tolerance value; it requires no datum reference.

Question 27: The frictional force is not affected by which of the following?

Area of contact (Correct answer)
Surface roughness
Force tending cause motion
Reaction of surface

Correct answer: Area of contact

Frictional force primarily depends on the normal force pressing the surfaces together and the coefficient of friction between those surfaces, which accounts for surface roughness. According to Amontons's Laws of Friction, the area of contact does not affect the magnitude of the frictional force. This is because while a larger area might distribute the normal force over more points, the actual microscopic contact area remains roughly proportional to the normal force, leading to a constant frictional force per unit normal force.

Question 28: What purposes does fluid mechanics serve?

Fluid mechanics enables to comprehend the behaviour of fluids under a variety of forces & atmospheric conditions
Fluid mechanics enables to comprehend the behaviour of fluids under various temperatures only (Correct answer)
Fluid mechanics enables to comprehend the behaviour of solid fluids under pressure
None of the mentioned

Correct answer: Fluid mechanics enables to comprehend the behaviour of fluids under various temperatures only

Fluid mechanics is a branch of mechanics concerned with the forces and flow of fluids. While it encompasses many aspects like pressure, velocity, and forces, temperature is a critical parameter that significantly influences fluid properties such as viscosity and density. Therefore, comprehending fluid behavior under various temperatures is indeed a key purpose, as temperature changes directly affect how fluids move and interact.

Question 29: Which of the following, according to thermodynamics and fluid mechanics, describes the temperature at a fluid flow's stagnation point?

Absolute temperature
Stagnation temperature (Correct answer)
Hydraulic temperature
Maximum temperature

Correct answer: Stagnation temperature

The stagnation temperature is the temperature a fluid would reach if it were brought to rest isentropically (reversibly and adiabatically) from its free-stream velocity. It represents the total energy (kinetic and internal) of the fluid expressed as a temperature. This concept is crucial in high-speed fluid flows, especially in aerodynamics, for understanding energy conversion.

Question 30: Vapour cavity creation is known as .

Emulsion
Static pressure drop
Cavitation (Correct answer)
Isentropic expansion

Correct answer: Cavitation

The creation of vapor cavities or bubbles in a liquid, typically due to a localized drop in pressure below the liquid's vapor pressure, is known as cavitation. In hydraulic machinery like turbines, these bubbles can form and then collapse violently as they move into higher pressure regions, causing noise, vibration, and significant damage to the turbine components.

Question 31: What does 'L10 life' represent for a rolling element bearing?

10% overload rating
10% of rated speed
Life at which 90% of bearings will survive (Correct answer)
10 million revolutions at zero load

Correct answer: Life at which 90% of bearings will survive

L10 life is the number of revolutions (or hours) at which 90% of a group of identical bearings will still be operating without fatigue failure.

Question 32: In first-angle projection (used outside the US), the front view is projected:

Onto the plane behind the object (Correct answer)
Directly below the object
Onto the plane in front of the object
Above and to the right

Correct answer: Onto the plane behind the object

In first-angle projection, the object is between the observer and the projection plane, so the front view is cast onto the plane behind the object.

Question 33: Which of the following best describes the fundamental tenet of fluid mechanics?

Momentum principle
Energy equation
Continuity equation
All of the mentioned (Correct answer)

Correct answer: All of the mentioned

The fundamental tenets of fluid mechanics are derived from the basic conservation laws applied to fluid systems. These include the continuity equation (representing conservation of mass), the momentum principle (representing conservation of momentum), and the energy equation (representing conservation of energy). All three principles are crucial for a complete analysis and understanding of fluid behavior in various engineering applications.

Question 34: In a Bode magnitude plot, a first-order lag factor (1 + jωT)^(−1) has a high-frequency asymptotic slope of:

−40 dB/decade
−20 dB/decade (Correct answer)
+40 dB/decade
+20 dB/decade

Correct answer: −20 dB/decade

A single real pole contributes a −20 dB/decade asymptote above its corner frequency (ω = 1/T), reflecting the −1 power in the denominator factor.

Question 35: A key connecting a gear to a shaft primarily transmits:

Shear force along the axis
Torque (Correct answer)
Axial force
Bending moment

Correct answer: Torque

A key is a machine element that fits into keyways on both the shaft and hub to transmit torque between them.

Question 36: Which of the following is a primary benefit of cellular manufacturing layout?

Lowest capital investment in equipment
Simplest production scheduling
Reduced material handling distance and faster throughput for part families (Correct answer)
Maximum machine utilization through large batch sizes

Correct answer: Reduced material handling distance and faster throughput for part families

Cellular manufacturing groups machines by part family, reducing material handling, work-in-process inventory, and lead time compared to functional layouts.

Question 37: The NTU method in heat exchanger analysis stands for:

Net Thermal Units
Normalized Temperature Uniformity
Number of Transfer Units (Correct answer)
Net Temperature Utilization

Correct answer: Number of Transfer Units

NTU (Number of Transfer Units) = UA/C_min is a dimensionless parameter representing the heat exchanger size relative to the minimum fluid capacity rate.

Question 38: The following rules apply to computations involving cable that is subject to its own weight:

Parallelogram law of addition of square root of their magnitudes
Parallelogram law of addition of square of their magnitudes
Parallelogram law of multiplication
Parallelogram law of addition (Correct answer)

Correct answer: Parallelogram law of addition

The Parallelogram Law of Addition is a fundamental principle in vector mechanics used to determine the resultant of two or more forces (vectors) acting at a common point. In cable computations, this law is essential for resolving and combining the various tensile forces and external loads acting on the cable segments to ensure equilibrium and analyze its behavior.

Question 39: Which microstructural feature of cast iron gives gray iron its characteristic fracture appearance and machinability?

Temper carbon in a ferritic matrix
Spheroidal graphite nodules
Massive carbide network at grain boundaries
Flake graphite in a pearlitic matrix (Correct answer)

Correct answer: Flake graphite in a pearlitic matrix

Gray iron contains graphite flakes that act as stress concentrators, causing fracture along the flakes and producing the characteristic gray fracture surface.

Question 40: In a just-in-time (JIT) production system, the kanban card primarily serves as a:

Quality inspection checklist
Signal to authorize production or material replenishment (Correct answer)
Machine maintenance schedule
Worker performance tracker

Correct answer: Signal to authorize production or material replenishment

A kanban card is a visual signal that authorizes upstream production or delivery of exactly the quantity consumed, pulling material through the system.

Question 41: Gyroscopic effects in a rotating machine cause:

Increased unbalance force
Increased damping
Precession of the spin axis when a torque is applied (Correct answer)
Reduced natural frequency

Correct answer: Precession of the spin axis when a torque is applied

A spinning body exhibits gyroscopic behavior where an applied moment causes precession — rotation of the spin axis perpendicular to the applied torque.

Question 42: The degree of reaction in the case of gas turbines and compressors is .

Isentropic enthalpy drop in rotor/ isentropic enthalpy drop in stage (Correct answer)
Static pressure drop in stage/ static pressure drop in rotor
Static temperature drop in stage/ static temperature drop in rotor
Static pressure drop in rotor/ static pressure drop in stage

Correct answer: Isentropic enthalpy drop in rotor/ isentropic enthalpy drop in stage

The degree of reaction in gas turbines and compressors is a dimensionless parameter that quantifies the proportion of the total isentropic enthalpy drop (or static pressure drop) occurring in the rotor blades relative to the entire stage (rotor plus stator). Specifically, it is defined as the ratio of the isentropic enthalpy drop in the rotor to the isentropic enthalpy drop in the stage. This parameter helps characterize the design and performance of turbomachinery.

Question 43: Which phase transformation occurs when austenite is rapidly quenched to form a body-centered tetragonal structure in steel?

Ferrite formation
Martensite formation (Correct answer)
Bainite formation
Pearlite formation

Correct answer: Martensite formation

Rapid quenching of austenite traps carbon in the BCC iron lattice, distorting it into a BCT martensitic structure.

Question 44: The damping ratio ζ = 1 corresponds to which type of damping?

Overdamped
Underdamped
Undamped
Critically damped (Correct answer)

Correct answer: Critically damped

Critical damping (ζ = 1) produces the fastest return to equilibrium without oscillation, defining the boundary between underdamped and overdamped behavior.

Question 45: In transient conduction, the lumped capacitance method is valid when:

Bi < 0.1 (Correct answer)
Re > 4000
Bi > 1
Pr > 1

Correct answer: Bi < 0.1

The lumped capacitance method assumes uniform temperature within the body and is valid when Bi < 0.1, meaning internal conduction resistance is negligible.

Question 46: For an ideal (inviscid, incompressible) fluid, Bernoulli's equation assumes which condition along a streamline?

Steady, incompressible, inviscid flow with no shaft work (Correct answer)
Viscous laminar flow with body forces only
Rotational flow with heat transfer
Unsteady turbulent flow

Correct answer: Steady, incompressible, inviscid flow with no shaft work

Bernoulli's equation applies along a streamline for steady, incompressible, inviscid flow with no external work done.

Question 47: The volute casing of a centrifugal pump is designed to:

Convert kinetic energy of the impeller discharge into pressure energy (Correct answer)
Increase fluid velocity before it reaches the impeller
Filter debris from the entering fluid stream
Cool the motor by circulating fluid around the casing

Correct answer: Convert kinetic energy of the impeller discharge into pressure energy

The volute's gradually increasing cross-sectional area decelerates the high-velocity fluid leaving the impeller, converting kinetic energy to pressure (diffusion).

Question 48: What does the 'pitch' of a thread refer to?

Thread angle
Axial distance between adjacent thread crests (Correct answer)
Thread diameter
Depth of thread

Correct answer: Axial distance between adjacent thread crests

Pitch is defined as the axial distance measured from one thread crest to the next adjacent crest on the same helix.

Question 49: Degenerate energy levels in the wave-mechanical model of an atom have:

Equal energy (Correct answer)
Electrons with the same spin
Equal number of electrons
Same shape

Correct answer: Equal energy

In the wave-mechanical model of an atom, degenerate energy levels refer to distinct quantum states that possess the same energy. For example, in a hydrogen atom, the 2s and 2p orbitals are degenerate (have the same energy) in the absence of external fields. While these states may differ in shape or angular momentum, their energy values are identical.

Question 50: Which of the following corresponds to the Blake number standard symbol?

b
Bl (Correct answer)
ba
Bi

Correct answer: Bl

The Blake number (Bl) is a dimensionless parameter used in fluid mechanics, particularly in the study of flow through porous media. It characterizes the ratio of inertial forces to viscous forces in such flows. This symbol helps in analyzing pressure drop and flow behavior in packed beds.

Question 51: In the k-ε turbulence model, the variable ε represents:

Turbulent kinetic energy
Eddy viscosity ratio
Turbulent Prandtl number
Rate of dissipation of turbulent kinetic energy (Correct answer)

Correct answer: Rate of dissipation of turbulent kinetic energy

In the k-ε model, k is turbulent kinetic energy and ε is the rate at which k is dissipated into heat by viscous action.

Question 52: Which dimensionless number represents the ratio of inertial forces to viscous forces in fluid flow, and is often relevant to heat transfer analysis?

Grashof number
Prandtl number
Nusselt number
Reynolds number (Correct answer)

Correct answer: Reynolds number

The Reynolds number Re = ρVL/μ represents the ratio of inertial to viscous forces and determines whether flow is laminar or turbulent.

Question 53: In the finite element method, the stiffness matrix [K] relates nodal forces to nodal displacements via [K]{u} = {F}. The stiffness matrix is always:

Symmetric and positive semi-definite before boundary conditions are applied (Correct answer)
Diagonal for any element type
Singular after boundary conditions are applied
Asymmetric and non-singular

Correct answer: Symmetric and positive semi-definite before boundary conditions are applied

The global stiffness matrix is symmetric (from reciprocity) and positive semi-definite (singular until supports are applied to remove rigid body modes).

Question 54: What is the dislocation in which Burgers vector and line direction are neither parallel nor perpendicular?

Jog dislocation
Mixed dislocation (Correct answer)
Edge dislocation
Screw dislocation

Correct answer: Mixed dislocation

A mixed dislocation is a type of crystal lattice defect that exhibits characteristics of both edge and screw dislocations. Its Burgers vector, which quantifies the lattice distortion, is neither purely perpendicular to the dislocation line (as in an edge dislocation) nor purely parallel (as in a screw dislocation). Instead, it has components of both, making it a combination of the two fundamental types.

Question 55: The Hertz contact stress formula is used to analyze failure in:

Rolling element bearings (Correct answer)
Bolted joints
Welds
Keyways

Correct answer: Rolling element bearings

Hertz contact stress theory is applied to rolling element bearings, gears, and cam-follower systems where curved surfaces make contact.

Question 56: Which of the following correctly defines the term 'plane strain' condition?

Only shear strains are non-zero
The strain state is uniaxial
All three principal strains are equal
Strain in one direction (usually z) is constrained to zero (Correct answer)

Correct answer: Strain in one direction (usually z) is constrained to zero

Plane strain occurs in thick components where strain in the thickness direction (ε_z = 0) is constrained by the surrounding material.

Question 57: The Avrami equation is used to describe:

Fatigue crack growth rate
Diffusion coefficient temperature dependence
Creep strain rate in metals
Kinetics of phase transformations (Correct answer)

Correct answer: Kinetics of phase transformations

The Avrami (JMAK) equation models the fraction of material transformed as a function of time during nucleation and growth processes.

Question 58: Dominant poles of a higher-order system are those located:

Closest to the imaginary axis in the left half-plane (Correct answer)
On the positive real axis
At the origin of the s-plane
Farthest from the imaginary axis in the left half-plane

Correct answer: Closest to the imaginary axis in the left half-plane

Dominant poles are closest to the imaginary axis (smallest magnitude of negative real part), so they decay most slowly and exert the greatest influence on the transient response.

Question 59: Which of the following statements regarding electrochemical machining is accurate?

It can also be used for all non-metals
Material is removed from the cathode and deposited on the anode (Correct answer)
Major drawback is that the finished product has residual stresses
Material is removed from the anode and carried away by the electrolyte

Correct answer: Material is removed from the cathode and deposited on the anode

In ECM, material is removed from an anode workpiece (positive pole) and moved to a cathode tool (negative pole) in an electrolyte bath, but instead of being deposited on the cathode, the electrolyte, which flows quickly between the two poles, carries the material away.

Question 60: Which pump characteristic curve feature indicates a stall or unstable operating region?

A rising portion of the H-Q curve at low flow rates (drooping characteristic) (Correct answer)
A continuously falling head-flow (H-Q) curve from zero to maximum flow
A perfectly flat efficiency curve across the operating range
A constant-power curve at all flow rates

Correct answer: A rising portion of the H-Q curve at low flow rates (drooping characteristic)

A rising (or humped) H-Q curve at low flows indicates potential instability because two different flow rates can produce the same head, leading to flow oscillation in parallel pump systems.

Question 61: Reynolds Transport Theorem relates the time rate of change of an extensive property in a:

Control volume to a system (material volume) (Correct answer)
Turbulent flow to its laminar equivalent
Pipe cross-section to its inlet conditions
Rotating frame to a stationary observer

Correct answer: Control volume to a system (material volume)

Reynolds Transport Theorem converts conservation laws from a Lagrangian system (fixed mass) to an Eulerian control volume formulation.

Question 62: Which of the following approaches is most frequently employed for analysis in fluid mechanics?

Langragian method
Eulerian Method (Correct answer)
Control volume analysis
None of the mentioned

Correct answer: Eulerian Method

The Eulerian method is most frequently employed for analysis in fluid mechanics because it describes fluid properties at fixed points in space as the fluid flows through them. This approach is highly practical for analyzing continuous flow fields, allowing engineers to study macroscopic fluid behavior without tracking individual particles. It simplifies the mathematical formulation for many common fluid dynamics problems.

Question 63: In a PID controller, which term is responsible for eliminating steady-state error?

Proportional (P) term
Derivative (D) term
Integral (I) term (Correct answer)
All three terms contribute equally

Correct answer: Integral (I) term

The integral term continuously accumulates error over time and generates an output that drives steady-state error to zero by adding an effective open-loop integrator.

Question 64: A section view in a drawing is used to:

Indicate surface finish
Show external features only
Show the part in an assembled state
Reveal internal features by cutting through the part (Correct answer)

Correct answer: Reveal internal features by cutting through the part

A section view cuts through the object along a cutting plane to reveal internal features that would otherwise be hidden, improving clarity.

Question 65: Which material has the highest thermal conductivity at room temperature?

Steel
Aluminum
Copper
Diamond (Correct answer)

Correct answer: Diamond

Diamond has the highest known thermal conductivity (~2000 W/m·K) of any natural material, far exceeding metals like copper (~400 W/m·K).

Question 66: A second-order system with damping ratio ζ = 0.5 is classified as:

Overdamped
Critically damped
Underdamped (Correct answer)
Undamped

Correct answer: Underdamped

An underdamped system has 0 < ζ < 1; with ζ = 0.5 the system exhibits oscillatory step response with overshoot that decays to the final value.

Question 67: The speed ratio (φ) of a Pelton wheel at maximum efficiency is approximately:

0.70 (bucket tip speed ≈ 70% of jet velocity)
0.26 (bucket tip speed ≈ 26% of jet velocity)
1.00 (bucket tip speed equals jet velocity)
0.46 (bucket tip speed ≈ 46% of jet velocity) (Correct answer)

Correct answer: 0.46 (bucket tip speed ≈ 46% of jet velocity)

Theoretical maximum efficiency for a Pelton wheel occurs when bucket speed is 0.5 × jet velocity, but friction reduces the optimum speed ratio to approximately 0.46 in practice.

Question 68: In torsion of non-circular cross-sections, Prandtl's stress function φ satisfies which governing equation?

∇⁴φ = 0 (biharmonic equation)
∇²φ = 0 (Laplace equation)
∂²φ/∂x² = Gθ
∇²φ = −2Gθ (Poisson's equation) (Correct answer)

Correct answer: ∇²φ = −2Gθ (Poisson's equation)

Prandtl's stress function satisfies the Poisson equation ∇²φ = −2Gθ within the cross-section, with φ = 0 on the boundary.

Question 69: For a blackbody, the emissivity (ε) equals:

0.5
Depends on temperature
1 (Correct answer)
0

Correct answer: 1

A blackbody is an ideal perfect emitter and absorber, defined by emissivity ε = 1; real surfaces have ε < 1.

Question 70: Which failure theory is most appropriate for ductile materials under static loading?

Maximum normal stress theory
Coulomb-Mohr theory
Maximum shear stress (Tresca) theory (Correct answer)
Maximum normal strain theory

Correct answer: Maximum shear stress (Tresca) theory

The Maximum Shear Stress (Tresca) theory is widely used for ductile materials and predicts yielding when the maximum shear stress reaches half the yield strength.

Question 71: A reaction turbine with inward radial flow is called .

Francis turbine (Correct answer)
Pelton turbine
Kaplan turbine
Propeller turbine

Correct answer: Francis turbine

The Francis turbine is a type of reaction turbine characterized by its inward radial flow design. Water enters the runner radially inward, flows through the blades, and exits axially. This design allows it to efficiently operate under a wide range of heads and flows, making it one of the most common types of hydraulic turbines used for medium-head applications.

Question 72: Around the turbine runner, the ___________ is made up of stationary circular wheels.

Drafting
Runner
Casing
Guide mechanism (Correct answer)

Correct answer: Guide mechanism

The guide mechanism, composed of a series of stationary guide vanes or wicket gates, is positioned around the turbine runner. Its primary function is to control the quantity of water flowing into the runner and to direct the water at the optimal angle of attack to the runner blades. This ensures efficient energy transfer from the water to the turbine.

Question 73: A material tested in tension shows a distinct upper and lower yield point followed by Lüders band propagation. This behavior is characteristic of:

Low-carbon steels with interstitial solute pinning (Correct answer)
Ceramic materials at room temperature
Face-centered cubic metals
Amorphous polymers above Tg

Correct answer: Low-carbon steels with interstitial solute pinning

In low-carbon steel, interstitial carbon and nitrogen atoms pin dislocations; the upper yield point corresponds to unpinning, after which Lüders bands propagate.

Question 74: What kind of dislocation inserts an extra plane into the crystal?

Edge dislocation (Correct answer)
Screw dislocation
Jog dislocation
Mixed dislocation

Correct answer: Edge dislocation

An edge dislocation is a linear crystal defect characterized by the termination of a plane of atoms within the crystal lattice. It can be visualized as an extra half-plane of atoms inserted into the crystal structure, causing localized stress and distortion. This specific configuration distinguishes it from other types of dislocations like screw or mixed dislocations.

Question 75: Which dimensionless number governs natural (free) convection?

Grashof number (Correct answer)
Peclet number
Stanton number
Reynolds number

Correct answer: Grashof number

The Grashof number Gr = gβΔTL³/ν² represents the ratio of buoyancy forces to viscous forces and governs natural convection.

Question 76: The Peierls-Nabarro stress is the theoretical stress required to:

Initiate crack propagation in a brittle material
Cause grain boundary sliding during creep
Nucleate a new phase from a supersaturated solid solution
Move a dislocation through a perfect crystal lattice (Correct answer)

Correct answer: Move a dislocation through a perfect crystal lattice

The Peierls-Nabarro stress represents the lattice friction stress that must be overcome to move a dislocation one Burgers vector in a perfect crystal.

Question 77: Which non-dimensional parameter characterizes the ratio of buoyancy forces to viscous forces in natural convection flows?

Eckert number
Prandtl number
Nusselt number
Grashof number (Correct answer)

Correct answer: Grashof number

The Grashof number (Gr = gβΔTL³/ν²) represents buoyancy to viscous force ratio in natural convection.

Question 78: The coefficient of performance (COP) of a heat pump is related to COP of a refrigerator operating between the same temperatures by:

COP_HP = COP_R
COP_HP = COP_R - 1
COP_HP = 1/COP_R
COP_HP = COP_R + 1 (Correct answer)

Correct answer: COP_HP = COP_R + 1

COP_HP = COP_R + 1, because the heat pump delivers both the heat removed from the cold reservoir plus the work input.

Question 79: Which machining process is best suited for producing highly accurate flat reference surfaces on cast iron machine tool bases?

Plunge EDM
Peripheral end milling
Surface grinding (Correct answer)
Broaching

Correct answer: Surface grinding

Surface grinding uses a rotating abrasive wheel traversing the workpiece, achieving flatness tolerances and surface finishes unattainable by milling on hardened machine tool components.

Question 80: D'Alembert's principle transforms a dynamic problem into an equivalent:

Thermal equilibrium problem
Fluid flow problem
Energy balance problem
Static equilibrium problem (Correct answer)

Correct answer: Static equilibrium problem

D'Alembert's principle introduces an inertia force (-ma) to convert the dynamic equation F = ma into a static equilibrium form ΣF = 0.

Question 81: The gain margin of a control system is measured at the frequency where the open-loop phase angle equals:

−180° (Correct answer)
+180°
−90°
0°

Correct answer: −180°

Gain margin is evaluated at the phase crossover frequency ωpc where ∠G(jω)H(jω) = −180°, and it equals the reciprocal of the open-loop magnitude at that frequency.

Question 82: What is cavitation in a centrifugal pump?

Formation and collapse of vapor bubbles due to local pressure drop below vapor pressure (Correct answer)
Blockage of impeller by solid particles
Reverse flow through the pump at low speeds
Air entrainment through the suction flange

Correct answer: Formation and collapse of vapor bubbles due to local pressure drop below vapor pressure

Cavitation occurs when local pressure falls below the liquid's vapor pressure, causing vapor bubbles that implode violently and damage pump components.

Question 83: In vibration analysis, a node point is where:

Frequency is minimum
Amplitude is maximum
Velocity is maximum
Amplitude is zero in a mode shape (Correct answer)

Correct answer: Amplitude is zero in a mode shape

A node is a point in a vibrating structure where the amplitude of motion is zero for a particular mode shape.

Question 84: Cavitation in hydraulic machinery occurs when the local fluid pressure drops below the:

Vapor pressure of the fluid (Correct answer)
Stagnation pressure
Atmospheric pressure
Critical pressure of the fluid

Correct answer: Vapor pressure of the fluid

Cavitation occurs when local static pressure falls below the fluid's vapor pressure, causing vapor bubble formation.

Question 85: When does a fluid become laminar?

Low viscosity
Reynolds number is less than 2000 (Correct answer)
The density of the fluid is high
Reynolds number is greater than 2000

Correct answer: Reynolds number is less than 2000

Laminar flow is characterized by smooth, orderly fluid motion where fluid particles move in parallel layers without significant mixing. This flow regime occurs when the Reynolds number, a dimensionless quantity, is below a critical value, typically around 2000 for flow in pipes. Below this threshold, viscous forces dominate over inertial forces, maintaining the orderly flow.

Question 86: What is currently the least expensive method of generating power?

Nuclear power
Thermal power
Electric Power
Hydroelectric power (Correct answer)

Correct answer: Hydroelectric power

While initial construction costs for hydroelectric power plants can be significant, their operational and maintenance costs are remarkably low compared to other power generation methods. Hydroelectric power utilizes a free and renewable fuel source (water), resulting in no fuel costs and minimal environmental emissions during operation. This makes it one of the most cost-effective methods for generating electricity over its long operational lifespan.

Question 87: A given element's many isotopes all share the same:

Number of protons (Correct answer)
Molar mass
Number of neutrons
Thermodynamic stability

Correct answer: Number of protons

Isotopes are atoms of the same chemical element, meaning they share the identical atomic number. The atomic number is defined by the number of protons in the nucleus, which uniquely determines the element's identity. Isotopes differ only in their number of neutrons, leading to variations in mass number but not in the fundamental elemental identity.

Question 88: The standard drawing projection method used in the United States is:

Cabinet projection
Oblique projection
Third-angle projection (Correct answer)
First-angle projection

Correct answer: Third-angle projection

Third-angle projection, identified by its symbol of a truncated cone with the small end toward the viewer, is the standard in the US per ASME/ANSI.

Question 89: A fluid flows through a pipe that suddenly expands in diameter. Using the continuity equation for incompressible flow, if the diameter doubles, the velocity will:

Remain the same
Decrease to one-quarter (Correct answer)
Halve
Double

Correct answer: Decrease to one-quarter

Continuity requires A₁V₁ = A₂V₂; doubling diameter quadruples area, so velocity decreases to one-quarter.

Question 90: The hydraulic energy that is converted into electricity is .

Mechanical power
Thermal power
Solar power
Hydroelectric power (Correct answer)

Correct answer: Hydroelectric power

Hydroelectric power is the specific term for electricity generated by harnessing the energy of moving water. In hydroelectric power plants, the potential energy of water stored at a height is converted into kinetic energy as it flows downwards, which then drives turbines connected to generators to produce electricity. This process directly converts hydraulic energy into electrical energy.

Question 91: Iron and carbon are the basic components of steels. Which of the aforementioned subgroups do they belong ?

Metallic Solid (Correct answer)
Polymer
Ceramics
Composites

Correct answer: Metallic Solid

Steels are alloys primarily composed of iron and carbon, with iron being a metal. The resulting material, steel, exhibits characteristic metallic properties such as high strength, conductivity, and malleability. Therefore, steels are classified as metallic solids, belonging to the broader category of metals and their alloys.

Question 92: In precipitation hardening (age hardening), the maximum strength is achieved at the stage called:

Underaging
Overaging
Solution treatment
Peak aging (Correct answer)

Correct answer: Peak aging

Peak aging produces the optimal precipitate size and distribution that maximally impedes dislocation motion, giving maximum hardness and strength.

Question 93: Which of the following best describes the shear center of a cross-section?

The centroid of the cross-section
The point through which a transverse load must act to produce no twisting (Correct answer)
The point of maximum shear stress
The point where normal stress is zero

Correct answer: The point through which a transverse load must act to produce no twisting

The shear center is the unique point where a transverse load causes pure bending without twisting of the beam.

Question 94: Radial flow reaction turbines' primary components are .

Draft tube
All of the mentioned (Correct answer)
Guide mechanism
Casing

Correct answer: All of the mentioned

Radial flow reaction turbines, like Francis turbines, require several key components for efficient operation. The casing (often a spiral or volute casing) directs water to the runner, the guide mechanism (guide vanes) controls the flow angle and quantity of water entering the runner, and the draft tube recovers kinetic energy from the water exiting the runner, all contributing to the turbine's overall performance.

Question 95: Which of the following corresponds to the Atwood number's standard symbol?

Ar
A (Correct answer)
a
AR

Correct answer: A

The Atwood number is a dimensionless quantity used in fluid dynamics to characterize the density difference between two fluids. It is conventionally represented by the capital letter 'A'. This number is particularly relevant in analyzing hydrodynamic instabilities, such as the Rayleigh-Taylor instability, where density stratification plays a crucial role.

Question 96: The concept of 'stress triaxiality' is important in fracture mechanics because higher triaxiality:

Increases ductility by spreading deformation uniformly
Suppresses plastic flow and promotes brittle cleavage fracture (Correct answer)
Has no effect on fracture mode
Reduces the yield stress required for plastic deformation

Correct answer: Suppresses plastic flow and promotes brittle cleavage fracture

High stress triaxiality (hydrostatic tension) constrains shear deformation, suppressing plasticity and making the material behave more brittlely.

Question 97: In fiber-reinforced composites, the rule of mixtures predicts longitudinal stiffness when fibers and matrix are loaded:

At 45° to fiber axis
In parallel (isostrain condition) (Correct answer)
In series (parallel loading)
Under hydrostatic pressure

Correct answer: In parallel (isostrain condition)

Under isostrain (parallel) loading along the fiber axis, both constituents experience the same strain, giving the upper-bound rule of mixtures for stiffness.

Question 98: During deep drawing of sheet metal, wrinkling of the flange is typically prevented by:

Increasing punch speed
Heating the blank above recrystallization temperature
Reducing the die clearance below material thickness
Applying a blank holder force to keep the flange flat (Correct answer)

Correct answer: Applying a blank holder force to keep the flange flat

A blank holder applies a controlled force to the sheet flange, suppressing compressive instability that would otherwise cause wrinkling as the material flows inward.

Question 99: In a centrifugal pump, the specific speed Ns is used to:

Determine pipe friction losses
Classify pump geometry and select the optimal impeller type (Correct answer)
Predict cavitation onset
Calculate NPSH available

Correct answer: Classify pump geometry and select the optimal impeller type

Specific speed classifies pump geometry: low Ns favors radial-flow (centrifugal) designs, high Ns favors axial-flow designs.

Question 100: What is the primary function of a fixture in a manufacturing setup?

Supplying cutting fluid to the tool
Cutting the workpiece to shape
Measuring dimensional accuracy after machining
Locating and clamping the workpiece accurately and repeatably during machining (Correct answer)

Correct answer: Locating and clamping the workpiece accurately and repeatably during machining

A fixture holds the workpiece in a precise, repeatable position and orientation relative to the cutting tool, ensuring dimensional consistency across multiple parts.

Philippine Mechanical Engineering Licensure Examination (MELE)

The Philippine Mechanical Engineering Licensure Examination (MELE) is administered by the Professional Regulation Commission (PRC) and tests BME graduates across Mathematics/Engineering Sciences, Power/Industrial Plant Engineering, and Machine Design to earn the Registered Mechanical Engineer (RME) license.

100

Questions

150 min

Time Limit

70%

To Pass

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