EngLab | Glossary of Terms & Symbols

Acceleration (a)

Rate of change of velocity of an object with respect to time.

Adhesion

Force of attraction between different substances, such as a liquid and a solid surface.

Airfoil

Shape designed to produce lift when air flows over it.

Axial Load (F_axial)

Force applied along the longitudinal axis of a structural member causing tension or compression.

Adiabatic Process

A thermodynamic process with no heat exchange with the surroundings.

Amplitude

Maximum displacement of a vibrating system from its equilibrium position.

Bending Moment (M)

Internal moment that induces bending of a beam due to applied loads.

Bernoulli’s Principle

Relationship describing the conservation of energy in a flowing fluid.

Boiling Point

Temperature at which a liquid changes into vapor at a given pressure.

Boltzmann Constant (k)

Fundamental constant relating temperature to energy in statistical mechanics.

Bulk Modulus (K)

Measure of a material’s resistance to uniform compression.

Capacitance (C)

Ability of a system to store electric charge per unit voltage.

Capillary Action

Ability of a liquid to flow in narrow spaces without external forces.

Centrifugal Force

Apparent outward force on a rotating object.

Centripetal Force

Force directed toward the center of a circular path causing circular motion.

Coefficient of Friction (μ)

Ratio of frictional force to normal force between surfaces.

Compressive Stress (σ_c)

Stress that tends to shorten or compress a material.

Conduction

Heat transfer through a solid material without movement of the material.

Convection

Heat transfer due to fluid motion.

Control Volume

Defined region in space used to analyze fluid flow and energy transfer.

Creep

Slow, permanent deformation of a material under constant stress over time.

Density (ρ)

Mass per unit volume of a substance.

Diode

Semiconductor device that allows current to flow in one direction only.

Displacement (s)

Vector representing change in position of an object.

Drag Force

Resistance force experienced by an object moving through a fluid.

Dynamic Viscosity (μ)

Resistance of a fluid to flow under an applied shear stress.

Elastic Limit

Maximum stress that a material can withstand without permanent deformation.

Elastic Modulus (E)

Material stiffness under elastic deformation.

Electrical Resistivity (ρ_e)

Property of a material that resists electrical current flow.

Electromotive Force (EMF)

Voltage generated by a source when no current is flowing.

Electron

Subatomic particle with negative electric charge.

Entropy (S)

Thermodynamic measure of disorder or randomness in a system.

Equilibrium

State where all forces or moments acting on a body are balanced.

Euler’s Formula

Relationship for polyhedra: V - E + F = 2, where V=vertices, E=edges, F=faces.

Exponential Decay

Process where a quantity decreases at a rate proportional to its current value.

Fatigue

Progressive structural damage under repeated cyclic loading.

Fluid Mechanics

Study of fluids in motion and at rest, and the forces on them.

Flow Rate (Q)

Volume of fluid passing through a cross-section per unit time.

Force (F)

Interaction that causes a change in motion of a body.

Force Diagram

Graphical representation of all forces acting on a body.

Free Body Diagram

Diagram showing all forces acting on a single object isolated from its environment.

Frequency (f)

Number of cycles per unit time for a periodic event.

Galvanometer

Device for detecting and measuring small electric currents.

Gauge Pressure

Pressure measured relative to atmospheric pressure.

Gear Ratio

Ratio of rotational speeds of two mating gears.

Gravitational Acceleration (g)

Acceleration due to gravity at the Earth’s surface (~9.81 m/s²).

Harmonic Motion

Periodic motion where the restoring force is proportional to displacement.

Heat Capacity (C)

Amount of heat required to raise the temperature of a substance by one degree.

Heat Transfer

Process of thermal energy moving from one body or substance to another.

Hooke’s Law

Stress is proportional to strain within the elastic limit of a material.

Hydraulic Diameter (D_h)

Characteristic length used to calculate flow parameters in non-circular conduits.

Hydraulic Head

Height of liquid column representing pressure in fluid systems.

Impulse

Product of force and the time over which it acts.

Inclined Plane

Flat surface tilted at an angle used to raise or lower objects with less force.

Inductance (L)

Property of a conductor to oppose change in current via magnetic field.

Internal Energy (U)

Total energy contained within a system, including kinetic and potential energies of molecules.

Isentropic Process

Thermodynamic process with constant entropy.

Isothermal Process

Thermodynamic process occurring at constant temperature.

Jacketed Vessel

Container surrounded by a secondary layer for heating or cooling of contents.

Joule (J)

SI unit of energy or work (1 N·m).

Kelvin (K)

SI unit of temperature, absolute scale starting at absolute zero.

Laminar Flow

Smooth, orderly fluid motion characterized by parallel layers.

Lap Joint

Type of joint where two materials overlap and are fastened together.

Load Factor

Ratio of actual load to design load.

Moment of Inertia (I)

Property that determines resistance to bending or rotation.

Mach Number (Ma)

Ratio of flow velocity to speed of sound in the medium.

Modulus of Rigidity (G)

Shear modulus of a material, measure of stiffness in shear.

Newton (N)

SI unit of force (kg·m/s²).

Natural Frequency

Frequency at which a system vibrates when disturbed.

Ohm (Ω)

SI unit of electrical resistance.

Overload

Condition where applied load exceeds design capacity.

Pascal (Pa)

SI unit of pressure (1 N/m²).

Power (P)

Rate of doing work or transferring energy (W = J/s).

Plastic Deformation

Permanent change in shape of a material under stress.

Poisson’s Ratio (ν)

Ratio of lateral strain to axial strain in a material under stress.

Pressure (P)

Force per unit area applied perpendicular to a surface.

Q Factor

Quality factor of a resonant system, ratio of stored energy to energy dissipated per cycle.

Quenching

Rapid cooling of a material to alter its mechanical properties.

Radiation

Transfer of heat in the form of electromagnetic waves without requiring a medium.

Reynolds Number (Re)

Dimensionless number indicating flow regime (laminar or turbulent).

Resilience

Ability of a material to absorb energy and return to its original shape.

Resistance (R)

Opposition to flow of current in an electrical circuit.

Shear Stress (τ)

Stress that acts parallel to the surface.

Strain (ε)

Deformation per unit length of a material.

Specific Heat (c)

Heat required to raise the temperature of 1 kg of substance by 1 K.

Stress (σ)

Internal resistance offered by a material to external force.

Surface Tension

Energy required to increase the surface area of a liquid due to intermolecular forces.

Thermal Conductivity (k)

Property describing heat transfer through a material.

Thermodynamic System

Defined portion of the universe under study for energy analysis.

Torque (τ)

Measure of rotational force applied to an object.

Ultimate Strength

Maximum stress a material can withstand before failure.

Unit Vector

Vector with magnitude of 1 indicating direction only.

Velocity (v)

Rate of change of position of an object.

Viscosity (μ)

Measure of fluid resistance to flow.

Volumetric Flow Rate (Q)

Volume of fluid passing through a section per unit time.

Work (W)

Energy transfer due to force applied over a distance.

X-axis

Horizontal axis in a Cartesian coordinate system used in engineering drawings or graphs.

Yield Strength (σ_y)

Stress at which a material begins to deform plastically.

Young’s Modulus (E)

Elastic modulus representing stiffness of a material in tension or compression.

Zero Deflection

Condition where a structural member experiences no displacement under applied load.

Engineering Glossary

Quick definitions of key engineering terms, symbols, and units

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