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Classical Mechanics Glossary

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  • Abrasion  -  The destruction of a material caused by scraping or rubbing against a rough, hard surface.
  • Abrasion Resistance  -  The ability to withstand scuffing, scratching, rubbing or deterioration due to physical contact.
  • Abrasive  -  A material that is able to remove the surface of another material.
  • Absolute Roughness  -  The measure of the roughness or irregularities on the internal surface of a pipe or conduit relative to the size of the pipe.  It is used in fluid dynamics and engineering, particularly in applications involving the flow of fluids through pipes, tubes, or channels.  The absolute roughness of a pipe's interior surface plays a significant role in determining the frictional resistance to fluid flow within the pipe.  The rougher the internal surface, the greater the frictional losses, and the more energy is required to pump or transport the fluid through the pipe.  Conversely, smoother internal surfaces result in lower frictional losses and are more energy efficient.
  • Absolute Vacuum  -  Contains no matter and can not be achieved.
  • Acceleration  -  The rate of change of velocity.  Whenever a mass experiences a force, an acceleration is acting.
  • Acceleration due to Gravity  -  The force on an object caused only by gravity.
  • Acceleration from Force  -  The mass and the net forces acting on the object.
  • Acceleration of Gravity  -  The force on an object caused only by gravity.
  • Affinity Laws  -  Express the mathematical relationship between the several variables involved in pump performance.
  • Air Resistance  -  A force that opposes an object as it moves through the air.
  • Allowable Stress  -  The maximum stress that a material can safely withstand under specific operating conditions.  It is determined by considering various factors such as the material's strength, its mechanical properties, and the desired level of safety.
  • Angular Acceleration  -  The rate at which the angular velocity of an object changes over time.  It represents how quickly an object's rotational speed or direction of rotation is changing. 
  • Angular Deflection  -  When a flex connector is bent on it's centerline.  One end of the hose assembly is deflected or bent with the other end remaining parallel.
  • Angular Deflection Length  -  The amount of rotational movement or deflection that a structural element or connection can tolerate before it reaches a critical point of failure or instability.  This concept is commonly encountered in engineering and construction, particularly in the design of structures and connections that are subjected to various loads and forces.
  • Angular Displacement  -  The angle through which a body moves in a circular path.  It is the change in the orientation or angular position of an object relative to a reference point or axis.  It is a measure of the angle through which an object has rotated or turned from its initial position to its final position.  Angular displacement can be either positive or negative, depending on the direction of rotation.  Conventionally, counterclockwise rotations are considered positive, while clockwise rotations are considered negative.
  • Angular Momentum  -  How much an object is rotating around a fixed point.
  • Angular Momentum of an Object with Linear Momentum  -  The porportion of the average net torque and the time interval the torque is applied to.
  • Angular Velocity  -  The speed that an object moves through an angle, θ.  The calculation below calculates ω but does not calculate the relative velocity of a point as it moves throughout the curve.
  • Angular Speed  -  The speed that an object moves through an angle, θ.  The calculation below calculates ω but does not calculate the relative velocity of a point as it moves throughout the curve.
  • Angular Velocity of a Rolling Sphere  -  Without slipping is the velocity of a point on the circumference (relative to the center of the sphere), divided by the radius of the sphere.
  • API Gravity  -  If a fluids API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks.
  • Applied Force  -  A force that is applied to an object by another object or system.  It is a vector quantity, meaning it has both magnitude and direction.  An applied force can cause an object to accelerate or change its direction of motion.
  • Area Moment of Inertia  -  The resistance of an object to bend around a certain axis of a area cross-section.
  • Atmospheric Pressure  -  The pressure exerted upon the earth's surface by the air because of the gravitational attraction of the earth.
  • Average Acceleration  -  The change of velocity over an elapsed amount of time.  Whereas, instantaneous accleration is the change of velocity at a specific point in time.
  • Average Angular Acceleration  -  The average rate at which the angle velocity changes with respect to time.
  • Average Angular Velocity Change in Velocity  -  When an object makes changes in its angular velocity at different times that is an average angular velocity of any given velocities.
  • Average Velovity Change in Velovity  -  When an object make changes in its velocity at different times that is an average velocity of any given velocities.
  • Axial Deflection  -  When a flex connector is compressed or stretched on it's centerline which usually occurs from the change in temperature.
  • Axial Force  -  The force acting parallel to the longitudinal x-axis.  Also called shear force.
  • Axial Stiffness  -  The ability of a structure or component to resist deformation or displacement along its axial or longitudinal direction.  It is a measure of the resistance to axial loads or forces applied parallel to the longitudinal axis of the object. 

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  • Beam Shear Stress  -  The horizontal shear stress of a beam.  It refers to the internal stressthat occurs within a beam when it is subjected to transverse or shear loads.  When a beam is loaded in such a way that forces are applied parallel to its cross-sectional plane, shear stresses develop along the beam's cross-section.
  • Breakaway Torque  -  The amount of force or torque required to overcome static friction and start the rotation of a stationary object.  This term is commonly used in mechanical engineering and physics, especially when dealing with rotating machinery, such as engines, gears, or bearings.  When an object is at rest and you want to set it in motion, you often have to apply a greater force or torque initially to overcome the static friction that is preventing it from moving.  Once the object starts moving, you typically need less force or torque to keep it in motion, which is known as kinetic friction.
  • Breakloose Torque  -  The torque required to effect reverse rotation when a pre-stressed threaded assembly is loosened.
  • Brinell Hardness Number  -  A measurement of a material's hardness of metals and alloys, specifically its resistance to indentation.  It is determined using the Brinell hardness test, which involves pressing a spherical indenter (usually a hardened steel ball) into the surface of the material under a known load.

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  • Centrifugal Acceleration  -  The motion of an object traveling in a circular path with respect to time.
  • Centrifugal Force  -  When a force pushes away from the center of a circle, but this does not really exist.
  • Centripetal Acceleration  -  The change in the velocity, which is a vector, either in speed or direction as an object makes its way around a circular path.
  • Centripetal Force  -  The force that makes an object follow a curved path.  It is a force generated when an object keeps traveling along a axis of rotation.
  • Change in Angular Momentum  -  The porportion of the average net torque and the time interval the torque is applied to.
  • Characteristic Length  -  A dimension used in physics that defines the scale of a physical system.
  • Characteristic Time  -  An estimate of the order of magnitude to the reaction time scale of a system.
  • Characteristic Velocity  -  Measure the effectiveness of the combustion of a rocket engine at high temperature and pressure, seperate from nozzle performance.
  • Circular Velocity  -  The velocity at which an object moves around a circle with a given radius.
  • Coefficient of Friction  -  The ratio between two contacting surfaces and the frictional force that resists the normal force of the object.
  • Collinear Force  -  All the forces share the same line of action.
  • Column Buckling Stress  -  The allowable buckling stress of a column.  It describes the stress at which a slender structural element, such as a column or beam, becomes unstable and fails due to lateral (buckling) deformation rather than direct compression.  When a compressive load is applied to a slender column, it tends to buckle or deflect laterally rather than uniformly compressing. This lateral deflection can lead to the failure of the column if it exceeds a certain critical value.
  • Compression  -  The force (pressure) acting on a material.  Compression is the process of reducing the volume or increasing the density of a substance, typically by applying external forces.  It involves the application of pressure to compress or squeeze a material, resulting in a decrease in its volume.
  • Concurrent Force  -  All of the forces act at the same point.
  • Conservation Law  -  States that the total energy of an isolated system remains constant and its physical properties are conserved over time.
  • Constant Acceleration  -  The constant rate in a straight line at which the velocity changes with respect to time.
  • Constant Angular Acceleration  -  An object is the constant rate at which the angle velocity changes with respect to time.
  • Coplannar Parallel Force  -  The forces can be in the same or opposite direction and are on the same plane.
  • Cross Product Operator  -  The cross product of two vectors.  It is a binary operation that takes two vectors as input and returns a third vector that is perpendicular to both of the input vectors.
  • Cyclic Deflection  -  The repeated change in temperature or vibration.
  • Cylinder Axial Stress  -  The longitudinal stress parallel to the axis along a cylinder or pipe having both ends closed due to internal pressure.
  • Cylinder Hoop Stress  - The circumference stress in a cylinder of pipe having both ends closed due to internal pressure.

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  • Deceleration  -  The rate of change of velocity, this is the opposite of acceleration.
  • Deflection  -  The change in the position of something from zero or from its normal position.
  • Deformation  -  Measured by how much an object is deformed from its origional dimensions.
  • Deformation Coefficient  -  The force restricting the movement of an object that is sliding or rolling and one or both surfaces are relatively soft and deformed by the forces.
  • Deformation Wear  -  A type of wear that occurs when two surfaces come into contact and undergo plastic deformation, resulting in material loss or surface damage.
  • Degradation  -  A deleterious change in the physical properties evidenced by impairment of these properties.
  • Deionization  -  The process which removes soluble matter from water by by ion exchange using natural or synthetic resins.
  • Density  -  The ratio of the amount of matter in an object compared to its volume.
  • Density of an Ideal Gas  -  Greatly affected by pressure.
  • Density of Material due to Temperature  -
  • Design Pressure  -  Also known as working pressure.  The normal pressure that a system operates at.
  • Differential  -  The quantitative difference between two or more forcespressuretime, etc.
  • Diffusion  -  The spread of gases, liquids, or solids from areas of high concentration to areas of low concentration.
  • Displacement  -  A term used in physics to describe the change in position of an object in a particular direction.  It is a vector quantity, meaning it has both magnitude and direction, some of these include acceleration, drag, force, lift, momentumthrusttorquevelocity, and weight.
  • Displacement Power  -  The amount of power required to displace an object a certain distance over time with a known force.
  • Distance  -  The dimension from one point to another point or the dimension from one end to the other end of an object.
  • Doppler Effect  -  The increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move toward (or away) each other.
  • Drag Coefficient  -  A force that opposes an object as it moves through the air.

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  • Efficiency  -  Expressed in percentage and always less than 100%.
  • Elastic Deformation  -  The reversible and temporary change in shape or size of a material when subjected to external forces or loads within its elastic limit.
  • Elastic Modulus  -  The ratio of the stress applied to a body or substance to the resulting strain within the elastic limits.
  • Elastic Modulus of Concrete  -  Valid for normal weight concrete.
  • Elasticity  -  Measures the stiffness of an elastic material.  Elasticity can deform under the influence of an applied force and return to their original shape and size once the force is removed.  It is the measure of a material's response to stress and strain.  When a force or stress is applied to a material, it causes a deformation or strain in the material. 
  • Elongation  -  The increase in length to which a material is to be stretched prior to rupture.
  • Elongation Percentage  -  The percentage of elongation at the fracture.
  • Energy  -  Never created or destroyed, First Law of Thermodynamics, but it can be transferred from one object to another.
  • Equilibrium  -  When all the net external forces that act upon an object are balanced.
  • Escape Velocity  -  The minimum velocity required to leave a planet or moon or the minimum velocity to overcome the pull of gravity.

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  • g-force  -  A force (force per unit mass) equal to one unit of gravity that is multiplied during a rapid change in direction or velocity.
  • Gas Oil Ratio  -  When oil is brought to surface conditions it is usual for some gas to come out of solution.  The ratio of a given volume of gas at standard pressure and temperature (STP) to a given volume of produced oil.
  • Graham's Law  -  The rate at which gases disperse is inversely proportional to the square root of their mass.
  • Graham's Law of Effusion  -  The rate at which gases disperse is inversely proportional to the square root of their mass.
  • Gravitation  -  A force pulling togeather all matter.
  • Gravitational Acceleration  -  The force on an object caused only by gravity.
  • Gravitational Field  -  A region of space where forces are exerted and affect anything that has mass. 
  • Gravitational Force  -  A force (force per unit mass) equal to one unit of gravity that is multiplied during a rapid change in direction or velocity.
  • Gravitational Potential Energy  -  The energy stored in an object due to its height above the earth.
  • Gravitational Mass  -  Measured by comparing the force of gravity of an unknown mass to the force of gravity of a known mass.
  • Gravity  -  The natural force of attraction between any two objects with mass.  It is the force that pulls all objects towards each other, and is responsible for keeping the planets in our solar system in orbit around the sun, and for keeping objects on the Earth's surface from floating away into space.  The strength of gravity between two objects depends on their masses and the distance between them. 
  • Gravity Scale  -  If a fluids API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks.

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  • Physical Properties  -  Those properties familiarly discussed in physics, for example, density, electrical conductivity, and thermal expansion coefficient, exclusive of those described under mechanical properties.
  • Plasma  -  It is everywhere in the universe and the most common of all matter.  Of all types of matter it is closest to a gas.
  • Plastic Deformation  -  The permanent and non-reversible change in shape or size of a material when subjected to external forces or loads beyond its elastic limit.
  • Poisson's Ratio  -  The elastic ratio between lateral strain and longitudinal strain.
  • Polar Moment of Inertia  -  Defines the resistance of a cross-section to torsional deformation, due only to the shape of the cross-section.
  • Potential Energy  -  The possessed energy by a body due to its relative position in a gravitational field.
  • Power  -  The rate of doing work or the rate of using energy per unit time.
  • Power Velocity  -
  • Pressure  -  The force exerted perpendicular to the surface of an object and is expressed as force per unit area.
  • Pressure Differential  -  The pressure difference between two points of a system.
  • Proof Stress  -  A specified stress to be applied to a member or structure to indicate its ability to withstand service loads.

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  • Radius of Gyration  -  The distance from the axis of rotation to a point where the total mass of the body is supposed to be concentrated.
  • Rate of Change in Acceleration  -  The time derivative of acceleration, the second derivative of velocity or the third derivative of position.
  • Rate of Change in Velocity  -  The first derivative of velocity, the second derivative of position or the instantaneous change in velocity.  In physics, it is known as acceleration.
  • Relativistic Mass  -  The mass of a body which changes with the speed of the body as this speed approaches close to the speed of light.
  • Resistance  -  The measure of the opposition to the flow of any physical quantity, not just electric current.
  • Rest Mass  -  When the body is at rest and motionless, and is also relative to an observer moving or not moving.
  • Resilience Modulus  -  The amount of energy a material can absorb and still return to its origional shape.
  • Rolling Coefficient  -  The combination of static, deformation and molecular coefficients of friction.
  • Rolling Rersistance  -  Occurs when a resistance force is applied to a rolling wheel.
  • Rotational Acceleration  -  The rate at which the angle velocity changes with respect to time.
  • Rotational Force  -
  • Rotational Inertia  -  Measures the resists or change an object has to rotational acceleration about an axis.
  • Rotational Kinetic Energy  -  The energy associated with the rotational motion of an object.  Just as translational kinetic energy is the energy of an object in linear motion, rotational kinetic energy is the energy of an object in rotational motion around an axis.
  • Rotational Momentum  -  How much an object is rotating around a fixed point.
  • Rotational Motion  -
  • Rotational Stiffness  -  The resist deformation of an object in response to an applied force.
  • Rotational Work  -  Overcoming resistance for a distance by force and then adding torque.

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  • Second Area Moment  -  The resistance of an object to bend around a certain axis of a area cross-section.
  • Second Moment of Area  -  The resistance of an object to bend around a certain axis of a area cross-section.
  • Service Factor  -  Used to reduce a strength value to obtain an engineering design stress.
  • Shear Carriage  -  Bottom section of the shear that rises when a cut is made and catches the pieces of scrap.  Located at the weld.
  • Shear Crack  -  A diagonal, transgranular crack caused by shear stresses.
  • Shear Force  -  The force acting perpendicular to the longitudinal x-axis.  Also called axial force. 
  • Shear Modulus  -  The ratio of the tangential force per unit area applied to a body or substance to the resulting tangential strain within the elastic limits.
  • Shear Modulus of Elasticity  -  The ratio of the tangential force per unit area applied to a body or substance to the resulting tangential strain within the elastic limits.
  • Strain  -  Opposing forces acting parrallel to the cross-section of a body.
  • Shear Strength  -  The stress requied to produce a fracture in the plane of ctoss-section, the condition of loading being so much that the directions of force and of resistance are parallel and opposite although their paths are offset a specified minimum amount.
  • Shear Stress  -  Tends to deform the material by breaking rather than stretching without changing the volume by restraining the object.
  • Solid  -  Has particles that are compressed together in an orderly pattern.
  • Specific Gravity  -  The density or ratio of any substance to another substance.  It sometimes may be called just gravity or relative density.
  • Specific Gravity of Gas  -  The ratio of the density of the gas to the density of air at a standard pressure and temperature.
  • Specific Gravity of Soil  -  The mass of solids in the soil compared to the mass of water at the same volume.
  • Specific Volume  -  A intensive variable whose physical quantity value does not depend on the amount of the substance for which it is measured.
  • Specific Weight  -  The weight per unit volume of a substance.
  • Specific Mass  -  The ratio of the amount of matter in an object compared to its volume.Speed  -  The rate of change or distance with time.
  • Speed of Light  -  A speed which remains constant irrespective of the speed of the source of the light or of the observer.
  • Speed of Sound  -  The distance traveled for a specific time through a medium from particle to particle.
  • Stagnation Pressure  -  The pressure a fluid exerts when the velocity of the fluid is zero.
  • Static Efficiency  -  Measure of an air mover's efficiency based on its air horsepower in terms of flow and static pressure vs. required shaft input power.
  • Static Friction  -  The force that resists relative movement and keeps objects at rest.
  • Static Pressure  -  The difference in air pressure between the suction side and pressure side of a blower.
  • Statics  -  Concerns itself with forces when no change in momentun occurs.
  • Stiffness  -  The resistance of the elastic deformation of an object that applies to both compression and tension.
  • Stopping Distance  -  When a vehicle is moving at a certain velocity then has to come to a complete stop, the distance from applying the brakes to complete stop is the stopping distance.
  • Strain  -  The deformation, stretched or compressed, of a material compared to its original length.
  • Strain Energy  -  The energy stored in an elastic body of the material undergoing deformation.
  • Stress  -  The force per unit area of cross-section.
  • Surface Fatigue Wear  -  Repeated rolling or sliding contact, in which the shear stresses bring about microcracks, particles and form wear pits that destroy the surface.
  • Surface Pressure  -  The lateral force per unit length applied on a line perperdicular to the force.
  • Surface Tension  -  The energy or force at the surface of a liquid that holds it together.

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  • Ultimate Tensile Strength  -  The maximum stress a material can resist before it starts to elongate.
  • Understressing  -  Applying a cyclic stress lower than the endurance limit.
  • Uniform Strain  -  The strain occuring prior to the beginning of localization of strain.

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  • Wear  -  Wear is brought about from the gradual removal of particles due to contacting surfaces in motion, usually sliding, generally as a result of mechanical action.
  • Weight  -  Weight is a force on an object accelerated by gravity.
  • Weight Density  -  The basic difference between density and weight is that weight is a measure of the amount of matter in an object, whereas density measures the amount of matter in a unit volume.
  • Weight Force  -  The force of gravity or the weight.
  • Wind Chill Factor  -  An index of the air temperature and the wind velocity.
  • Wind Energy  -  The kinetic energy of air in motion.
  • Work Done by Gas  -  The product of force and distance but for gas work is pressure and the volume during the change in volume.
  • Work Energy Theorem  -  The change in the kinetic energy of an object is equal to the net work done on the object.
  • Working Pressure  -  The normal pressure that a system operates at.  Also known as design pressure.

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