Mechanical Engineering Basics Practice Exam

Question 1 Mechanical Engineering Basics

Define density in fluid mechanics.

If two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other. Heat transfer rate by convection: Q = hA(T_s − T_∞), where h is the convection coefficient. Mass per unit volume: ρ = m/V, typically in kg/m³. The maximum efficiency of a heat engine operating between two temperatures: η = 1 − T_cold/T_hot (temperatures in Kelvin).

Question 2 Mechanical Engineering Basics

What are the three modes of heat transfer?

The rotational equivalent of force: T = F × r, where r is the perpendicular distance from the axis of rotation. Conduction (through a solid), convection (via fluid motion), and radiation (via electromagnetic waves). A process that occurs at constant temperature (ΔT = 0). Within the elastic limit, stress is proportional to strain: σ = Eε, where E is Young's modulus.

Question 3 Mechanical Engineering Basics

What is 1 horsepower in watts?

The impulse (force × time) equals the change in momentum: FΔt = Δ(mv). 1 hp ≈ 745.7 W. A dimensionless number Re = ρvD/μ that predicts whether flow is laminar or turbulent. PV = nRT, where P is pressure, V is volume, n is moles, R is the universal gas constant, and T is absolute temperature.

Question 4 Mechanical Engineering Basics

What is creep?

The ratio of deformation to original length: ε = ΔL/L₀ (dimensionless). σ = My/I, where M is bending moment, y is distance from neutral axis, and I is moment of inertia. Acceleration directed toward the center of a circular path: a_c = v²/r = ω²r. Time-dependent, permanent deformation of a material under constant stress at elevated temperature.

Question 5 Mechanical Engineering Basics

Define factor of safety.

Kinematics describes motion without regard to forces; kinetics relates forces to the resulting motion. The ratio of a material's failure strength to the actual applied stress: FoS = σ_failure / σ_actual. To convert rotary motion into linear motion (or vice versa) and transmit power, e.g., in jacks and presses. The geometric center of an area or volume; the point where the body would balance perfectly if supported there.

Question 6 Mechanical Engineering Basics

What is Pascal's Law?

For steady, incompressible, inviscid flow: P + ½ρv² + ρgh = constant along a streamline. The ratio of shear stress to shear strain: G = τ/γ. Pressure applied to a confined fluid is transmitted equally in all directions throughout the fluid. Heat cannot spontaneously flow from a colder body to a hotter body without external work.

Question 7 Mechanical Engineering Basics

What is the relationship between E, G, and ν?

The Newton (N), defined as 1 kg·m/s². 1 atm = 101,325 Pa. G = E / [2(1 + ν)], linking Young's modulus, shear modulus, and Poisson's ratio. The sum of all moments about any point must equal zero: ΣM = 0.

Question 8 Mechanical Engineering Basics

Define strain in materials science.

The sum of all forces acting on a body must equal zero: ΣF = 0. The ratio of deformation to original length: ε = ΔL/L₀ (dimensionless). Pouring molten metal into a mold and allowing it to solidify into the desired shape. 1 bar = 100,000 Pa (10⁵ Pa).

Question 9 Mechanical Engineering Basics

What is a power screw used for?

1 bar = 100,000 Pa (10⁵ Pa). τ = Tr/J, where T is torque, r is radial distance, and J is the polar moment of inertia. G = E / [2(1 + ν)], linking Young's modulus, shear modulus, and Poisson's ratio. To convert rotary motion into linear motion (or vice versa) and transmit power, e.g., in jacks and presses.

Question 10 Mechanical Engineering Basics

What is the SI unit of power?

Metals and alloys that contain iron as the primary element, such as steel and cast iron. The Watt (W), defined as 1 J/s. Log Mean Temperature Difference: LMTD = (ΔT₁ − ΔT₂) / ln(ΔT₁/ΔT₂), used to calculate heat exchanger performance. τ = Tr/J, where T is torque, r is radial distance, and J is the polar moment of inertia.

Question 11 Mechanical Engineering Basics

What is the difference between MIG and TIG welding?

Failure that occurs under repeated cyclic loading at stress levels below the material's static ultimate strength. A slot machined into a shaft and hub to receive a key that transmits torque between them. MIG (GMAW) uses a consumable wire electrode and is faster; TIG (GTAW) uses a non-consumable tungsten electrode for more precise welds. Time-dependent, permanent deformation of a material under constant stress at elevated temperature.

Question 12 Mechanical Engineering Basics

State the Second Law of Thermodynamics (Clausius statement).

A manufacturing process where molten plastic is injected into a mold cavity under high pressure, then cooled to form the part. Heat cannot spontaneously flow from a colder body to a hotter body without external work. MIG (GMAW) uses a consumable wire electrode and is faster; TIG (GTAW) uses a non-consumable tungsten electrode for more precise welds. G = E / [2(1 + ν)], linking Young's modulus, shear modulus, and Poisson's ratio.

Question 13 Mechanical Engineering Basics

What is a gear ratio?

A body immersed in a fluid experiences a buoyant force equal to the weight of the fluid displaced. A roller provides one reaction force (normal to surface); a pin provides two reaction forces (horizontal and vertical). A material property measuring its ability to conduct heat: k, in units of W/(m·K). Metals have high k; insulators have low k. The ratio of the number of teeth (or diameters) of two meshing gears: GR = N₂/N₁ = ω₁/ω₂.

Question 14 Mechanical Engineering Basics

What is an alloy?

A dimensionless number Re = ρvD/μ that predicts whether flow is laminar or turbulent. For steady, incompressible, inviscid flow: P + ½ρv² + ρgh = constant along a streamline. A mixture of two or more elements, at least one being a metal, designed to achieve improved mechanical or chemical properties. Heat cannot spontaneously flow from a colder body to a hotter body without external work.

Question 15 Mechanical Engineering Basics

What is the mechanical advantage of a lever?

The entropy of a perfect crystal approaches zero as the temperature approaches absolute zero (0 K). For steady, incompressible, inviscid flow: P + ½ρv² + ρgh = constant along a streamline. The ratio of output force to input force: MA = F_out/F_in = d_in/d_out (distance ratio). Pouring molten metal into a mold and allowing it to solidify into the desired shape.

Question 16 Mechanical Engineering Basics

What is turning on a lathe?

Hot working is performed above the recrystallization temperature; cold working is below it and increases hardness via strain hardening. A machining process where a workpiece rotates against a stationary cutting tool to produce cylindrical shapes. G = E / [2(1 + ν)], linking Young's modulus, shear modulus, and Poisson's ratio. A single value combining conduction, convection, and fouling resistances: Q = UAΔT.

Question 17 Mechanical Engineering Basics

What is the torsion formula for a circular shaft?

A sketch of a body isolated from its surroundings showing all external forces and moments acting on it. τ = Tr/J, where T is torque, r is radial distance, and J is the polar moment of inertia. No heat engine can convert all absorbed heat into work; some heat must be rejected to a cold reservoir. A thermodynamic property defined as H = U + PV, representing internal energy plus flow work.

Question 18 Mechanical Engineering Basics

Define specific heat capacity.

MIG (GMAW) uses a consumable wire electrode and is faster; TIG (GTAW) uses a non-consumable tungsten electrode for more precise welds. The amount of heat required to raise the temperature of a unit mass by one degree: c = Q/(mΔT). The maximum stress a material can withstand before necking begins in a tensile test. The geometric center of an area or volume; the point where the body would balance perfectly if supported there.

Question 19 Mechanical Engineering Basics

What is casting as a manufacturing process?

Pouring molten metal into a mold and allowing it to solidify into the desired shape. A process in which no heat is transferred between the system and its surroundings (Q = 0). τ = Tr/J, where T is torque, r is radial distance, and J is the polar moment of inertia. Shaping metal using compressive forces, typically with a hammer or press, to improve grain structure and strength.

Question 20 Mechanical Engineering Basics

How do springs combine in parallel?

A₁v₁ = A₂v₂; the product of cross-sectional area and velocity is constant along a streamline. The equivalent stiffness is: k_eq = k₁ + k₂ + … (stiffer than any individual spring). The ratio of normal stress to normal strain in the elastic region: E = σ/ε, measured in Pa. The entropy of a perfect crystal approaches zero as the temperature approaches absolute zero (0 K).

Question 21 Mechanical Engineering Basics

What is the impulse-momentum theorem?

The impulse (force × time) equals the change in momentum: FΔt = Δ(mv). Hot working is performed above the recrystallization temperature; cold working is below it and increases hardness via strain hardening. Metals and alloys that contain iron as the primary element, such as steel and cast iron. Pressure applied to a confined fluid is transmitted equally in all directions throughout the fluid.

Question 22 Mechanical Engineering Basics

Define stress in materials science.

Shaping metal using compressive forces, typically with a hammer or press, to improve grain structure and strength. Force per unit area acting on a material: σ = F/A, measured in Pascals (Pa). Heat cannot spontaneously flow from a colder body to a hotter body without external work. A roller provides one reaction force (normal to surface); a pin provides two reaction forces (horizontal and vertical).

Question 23 Mechanical Engineering Basics

What is thermal conductivity?

A material property measuring its ability to conduct heat: k, in units of W/(m·K). Metals have high k; insulators have low k. The ratio of the number of teeth (or diameters) of two meshing gears: GR = N₂/N₁ = ω₁/ω₂. P = Tω, where P is power (W), T is torque (N·m), and ω is angular speed (rad/s). The ratio of output force to input force: MA = F_out/F_in = d_in/d_out (distance ratio).

Question 24 Mechanical Engineering Basics

State Hooke's Law.

The ratio of lateral strain to axial strain: ν = −ε_lateral/ε_axial, typically 0.25–0.35 for metals. Within the elastic limit, stress is proportional to strain: σ = Eε, where E is Young's modulus. σ = My/I, where M is bending moment, y is distance from neutral axis, and I is moment of inertia. Failure that occurs under repeated cyclic loading at stress levels below the material's static ultimate strength.

Question 25 Mechanical Engineering Basics

What is the continuity equation for incompressible flow?

A₁v₁ = A₂v₂; the product of cross-sectional area and velocity is constant along a streamline. Failure that occurs under repeated cyclic loading at stress levels below the material's static ultimate strength. No heat engine can convert all absorbed heat into work; some heat must be rejected to a cold reservoir. Time-dependent, permanent deformation of a material under constant stress at elevated temperature.

Question 26 Mechanical Engineering Basics

State the Zeroth Law of Thermodynamics.

The rotational equivalent of force: T = F × r, where r is the perpendicular distance from the axis of rotation. Within the elastic limit, stress is proportional to strain: σ = Eε, where E is Young's modulus. A measure of molecular disorder or energy dispersal in a system: dS = δQ_rev / T. If two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other.

Question 27 Mechanical Engineering Basics

What is D'Alembert's principle?

G = E / [2(1 + ν)], linking Young's modulus, shear modulus, and Poisson's ratio. M = F × d, where F is the force magnitude and d is the perpendicular distance from the point to the line of action. The ratio of a material's failure strength to the actual applied stress: FoS = σ_failure / σ_actual. By adding an inertial force −ma to a dynamic system, it can be analyzed as if in static equilibrium.

Question 28 Mechanical Engineering Basics

What is thermal expansion?

The amount of heat required to raise the temperature of a unit mass by one degree: c = Q/(mΔT). Pressure applied to a confined fluid is transmitted equally in all directions throughout the fluid. A thermodynamic property defined as H = U + PV, representing internal energy plus flow work. The tendency of a material to change dimensions with temperature: ΔL = αL₀ΔT, where α is the coefficient of thermal expansion.

Question 29 Mechanical Engineering Basics

What is the difference between a roller support and a pin support?

A journal bearing uses a fluid film for sliding contact; a rolling-element bearing uses balls or rollers to reduce friction. Heat transfer rate by convection: Q = hA(T_s − T_∞), where h is the convection coefficient. P = Tω, where P is power (W), T is torque (N·m), and ω is angular speed (rad/s). A roller provides one reaction force (normal to surface); a pin provides two reaction forces (horizontal and vertical).

Question 30 Mechanical Engineering Basics

What is Newton's First Law of Motion?

A body remains at rest or in uniform motion unless acted upon by a net external force. Radiant heat from a black body: Q = σεAT⁴, where σ = 5.67×10⁻⁸ W/m²K⁴ and ε is emissivity. The ratio of the number of teeth (or diameters) of two meshing gears: GR = N₂/N₁ = ω₁/ω₂. The geometric center of an area or volume; the point where the body would balance perfectly if supported there.

Question 31 Mechanical Engineering Basics

What is the SI unit of pressure?

A material's resistance to localized plastic deformation (indentation or scratching), measured by Brinell, Rockwell, or Vickers tests. σ = My/I, where M is bending moment, y is distance from neutral axis, and I is moment of inertia. If two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other. The Pascal (Pa), defined as 1 N/m².

Question 32 Mechanical Engineering Basics

What is hardness in materials science?

A material's resistance to localized plastic deformation (indentation or scratching), measured by Brinell, Rockwell, or Vickers tests. Shaping metal using compressive forces, typically with a hammer or press, to improve grain structure and strength. The net work done on a body equals the change in its kinetic energy: W_net = ΔKE = ½mv₂² − ½mv₁². Heat cannot spontaneously flow from a colder body to a hotter body without external work.

Question 33 Mechanical Engineering Basics

What is Newton's Third Law of Motion?

I = I_c + Ad², where I_c is the moment of inertia about the centroid, A is area, and d is the distance between axes. For every action there is an equal and opposite reaction: F₁₂ = −F₂₁. A mixture of two or more elements, at least one being a metal, designed to achieve improved mechanical or chemical properties. The ratio of a material's failure strength to the actual applied stress: FoS = σ_failure / σ_actual.

Question 34 Mechanical Engineering Basics

Define a heat exchanger's LMTD.

The ratio of normal stress to normal strain in the elastic region: E = σ/ε, measured in Pa. Log Mean Temperature Difference: LMTD = (ΔT₁ − ΔT₂) / ln(ΔT₁/ΔT₂), used to calculate heat exchanger performance. A fabrication process that joins materials by applying heat, pressure, or both to fuse them together. The tendency of a material to change dimensions with temperature: ΔL = αL₀ΔT, where α is the coefficient of thermal expansion.

Question 35 Mechanical Engineering Basics

At what Reynolds number does pipe flow typically transition from laminar to turbulent?

M = F × d, where F is the force magnitude and d is the perpendicular distance from the point to the line of action. A measure of molecular disorder or energy dispersal in a system: dS = δQ_rev / T. The Joule (J), defined as 1 N·m. The critical Reynolds number for pipe flow is approximately Re ≈ 2300.

Question 36 Mechanical Engineering Basics

What is an adiabatic process?

A single value combining conduction, convection, and fouling resistances: Q = UAΔT. The product of mass and velocity: p = mv. It is a vector quantity. A process in which no heat is transferred between the system and its surroundings (Q = 0). The maximum efficiency of a heat engine operating between two temperatures: η = 1 − T_cold/T_hot (temperatures in Kelvin).

Question 37 Mechanical Engineering Basics

What is a statically determinate structure?

A structure where all unknown reactions can be found using the equations of equilibrium alone. A slot machined into a shaft and hub to receive a key that transmits torque between them. A process that occurs at constant temperature (ΔT = 0). A machining process using a rotating multi-point cutter to remove material from a stationary workpiece.

Question 38 Mechanical Engineering Basics

What is 1 atmosphere in Pascals?

The amount of heat required to raise the temperature of a unit mass by one degree: c = Q/(mΔT). A structure where all unknown reactions can be found using the equations of equilibrium alone. 1 atm = 101,325 Pa. A material's resistance to localized plastic deformation (indentation or scratching), measured by Brinell, Rockwell, or Vickers tests.

Question 39 Mechanical Engineering Basics

What is centripetal acceleration?

Acceleration directed toward the center of a circular path: a_c = v²/r = ω²r. A dimensionless number Re = ρvD/μ that predicts whether flow is laminar or turbulent. The ratio of output force to input force: MA = F_out/F_in = d_in/d_out (distance ratio). The net work done on a body equals the change in its kinetic energy: W_net = ΔKE = ½mv₂² − ½mv₁².

Question 40 Mechanical Engineering Basics

What is the difference between laminar and turbulent flow?

Laminar flow has smooth, orderly layers; turbulent flow has chaotic, irregular fluctuations and higher mixing. The ratio of output force to input force: MA = F_out/F_in = d_in/d_out (distance ratio). A thermodynamic property defined as H = U + PV, representing internal energy plus flow work. A machining process where a workpiece rotates against a stationary cutting tool to produce cylindrical shapes.

Question 41 Mechanical Engineering Basics

What is a free body diagram (FBD)?

Time-dependent, permanent deformation of a material under constant stress at elevated temperature. A thermodynamic property defined as H = U + PV, representing internal energy plus flow work. A sketch of a body isolated from its surroundings showing all external forces and moments acting on it. The ratio of applied force to displacement: k = F/δ, in N/m. Higher k means a stiffer spring.

Question 42 Mechanical Engineering Basics

How do springs combine in series?

A sketch of a body isolated from its surroundings showing all external forces and moments acting on it. Log Mean Temperature Difference: LMTD = (ΔT₁ − ΔT₂) / ln(ΔT₁/ΔT₂), used to calculate heat exchanger performance. A machining process using a rotating multi-point cutter to remove material from a stationary workpiece. The equivalent stiffness is: 1/k_eq = 1/k₁ + 1/k₂ + … (lower than any individual spring).

Question 43 Mechanical Engineering Basics

What is milling?

A machining process using a rotating multi-point cutter to remove material from a stationary workpiece. 1 BTU ≈ 1055.06 J. The ratio of applied force to displacement: k = F/δ, in N/m. Higher k means a stiffer spring. The ratio of deformation to original length: ε = ΔL/L₀ (dimensionless).

Question 44 Mechanical Engineering Basics

State Archimedes' Principle.

τ = Tr/J, where T is torque, r is radial distance, and J is the polar moment of inertia. Log Mean Temperature Difference: LMTD = (ΔT₁ − ΔT₂) / ln(ΔT₁/ΔT₂), used to calculate heat exchanger performance. The Pascal (Pa), defined as 1 N/m². A body immersed in a fluid experiences a buoyant force equal to the weight of the fluid displaced.

Question 45 Mechanical Engineering Basics

Define the moment of a force about a point.

To convert rotary motion into linear motion (or vice versa) and transmit power, e.g., in jacks and presses. A dimensionless number Re = ρvD/μ that predicts whether flow is laminar or turbulent. Pouring molten metal into a mold and allowing it to solidify into the desired shape. M = F × d, where F is the force magnitude and d is the perpendicular distance from the point to the line of action.

Question 46 Mechanical Engineering Basics

What is the relationship between power, torque, and angular velocity?

Two equal, opposite, and non-collinear forces that produce a pure rotational effect (moment) with no net translational force. To reduce friction and support loads between moving parts (shaft and housing). P = Tω, where P is power (W), T is torque (N·m), and ω is angular speed (rad/s). The sum of all forces acting on a body must equal zero: ΣF = 0.

Question 47 Mechanical Engineering Basics

What is the Reynolds number?

The net work done on a body equals the change in its kinetic energy: W_net = ΔKE = ½mv₂² − ½mv₁². A dimensionless number Re = ρvD/μ that predicts whether flow is laminar or turbulent. τ = Tr/J, where T is torque, r is radial distance, and J is the polar moment of inertia. The equivalent stiffness is: k_eq = k₁ + k₂ + … (stiffer than any individual spring).

Question 48 Mechanical Engineering Basics

What is the overall heat transfer coefficient (U)?

The amount of heat required to raise the temperature of a unit mass by one degree: c = Q/(mΔT). A process that occurs at constant temperature (ΔT = 0). A single value combining conduction, convection, and fouling resistances: Q = UAΔT. No heat engine can convert all absorbed heat into work; some heat must be rejected to a cold reservoir.

Question 49 Mechanical Engineering Basics

What is the difference between hot working and cold working?

Acceleration directed toward the center of a circular path: a_c = v²/r = ω²r. τ = Tr/J, where T is torque, r is radial distance, and J is the polar moment of inertia. Hot working is performed above the recrystallization temperature; cold working is below it and increases hardness via strain hardening. The ratio of the number of teeth (or diameters) of two meshing gears: GR = N₂/N₁ = ω₁/ω₂.

Question 50 Mechanical Engineering Basics

What is the critical speed of a shaft?

Stress acting parallel (tangential) to a surface: τ = V/A, where V is the shear force. The rate of change of angular displacement: ω = dθ/dt, measured in rad/s. A machining process where a workpiece rotates against a stationary cutting tool to produce cylindrical shapes. The rotational speed at which a shaft's natural frequency of vibration matches the operating speed, risking resonance.