ABOUT -A POINT, -AN AXIS, -A LINE, -THE [XYZ]-AXIS
WITH REFERENCE TO OR AROUND A POINT
ABSOLUTE MAXIMUM SHEAR STRAIN
MAXIMUM PRESSURE CAUSING A SHEAR DEFORMATION OF AN OBJECT.
ABSOLUTE PRESSURE
A MEASURE OF THE TOTAL FORCE EXERTED PER UNIT OF AREA
ABSOLUTE/RELATIVE MOTION
MOTION OF OBJECTS AS MEASURED FROM DIFFERENT REFERENCE POSITIONS
ABUTMENT
ACCELERATION
RATE OF CHANGE OF VELOCITY OF AN OBJECT
ADJACENT
NEXT TO
ALGEBRAIC SUM
ALONG A LINE
IN THE DIRECTION OF A LINE
AMERICAN WIRE GAUGE
AMPLITUDE
THE HEIGHT OF A WAVE
ANALYTICAL METHODS
ANALYTICALLY
TO USE MATHEMATICAL ANALYSIS FOR A SOLUTION
ANGLE
A MEASURE OF A CHANGE IN DIRECTION THAT COMMONLY USES UNITS OF DEGREES OR RADIANS
ANGLE OF ROTATION
THE ANGLE THAT AN OBJECT ROTATES
ANGLE OF STATIC FRICTION
ANGLE OF TWIST
THE ANGLE THAT AN OBJECT IS TWISTED OR ROTATED
ANGULAR ACCELERATION
A MEASURE OF HOW FAST THE ANGULAR VELOCITY (ROTATION RATE) IS INCREASING
ANGULAR ACCELERATION
A MEASURE OF HOW QUICKLY THE ANGULAR VELOCITY OF AN OBJECT INCREASES
ANGULAR IMPULSE
A MEASURE OF THE ROTATION EFFECT OF A TORQUE THAT IS APPLIED TO AN OBJECT
FOR A SHORT TIME
ANGULAR MOMENTUM
A MEASURE OF THE ROTATIONAL MOTION THAT AN OBJECT HAS
ANGULAR NATURAL FREQUENCY
THE NUMBER OF OSCILLATIONS PER SECOND THAT AN OBJECT ONDERGOES IN ITS
NATURAL MOTION
ANGULAR VELOCITY
A MEASURE OF HOW QUICKLY AN OBJECT ROTATES ABOUT AN AXIS
ANISOTROPIC
AN OBJECT OR MATERIAL THAT IS NOT THE SAME THROUGHOUT (NONHOMOGENEOUS).
IT HAS DIFFERENT PROPERTIES OR DIFFERENT CHARACTERISTICS ALONG DIFFERENT
DIRECTIONS.
APPLIED FORCE
ONE OF THE FORCES THAT PUSHES OR PULLS ON AN OBJECT
ARBITRARY
OF AN UNSPECIFIED NATURE, UNDETERMINED, UNKNOWN
ARBITRARY DISTANCE
GOOD OR TRUE FOR ANY DISTANCE
ARBITRARY PARTICLES
PARTICLES IN ANY POSITION WITH ANY MASS, VELOCITIES,...
ARBITRARY PATH
ARBITRARY PLANE
ANY FLAT, INFINITE SURFACE (ANY ORIENTATION)
ARCH BRIDGE
AREA
A MEASURE OF SURFACE SIZE
AS A FUNCTION OF TIME
SHOW HOW A QUANTITY (TEMPERATURE, DISTANCE, ...) CHANGES AS TIME INCREASES
ASYMPTOTE
A LIMITING LINE OR CURVE
ASYMPTOTIC VALUE
A VALUE THAT IS APPROACHED IN A LIMITING PROCESS
AXIAL COMPRESSION
AXIAL DIRECTION
POINTING ALONG A ROTATIONAL AXIS OF AN OBJECT OR THE AXIS OF SYMMETRY OF
AN OBJECT (LIKE A CYLINDER)
AXIAL EXTENSION
AXIAL FORCE
A FORCE APPLIED PARALLEL TO THE SYMMETRY AXIS OF AN OBJECT
AXIAL LOAD
A FORCE APPLIED PARALLEL TO THE SYMMETRY AXIS OF AN OBJECT
AXIALLY LOADED BAR
AXIS
AN IMAGINARY LINE THAT SERVES AS A CENTER OF ROTATION OR A REFERENCE LINE
AXIS OF ROTATION
AN IMAGINARY LINE THAT SERVES AS THE CENTER FOR AN OBJECT ROTATING
IN SPACE
AXIS OF SYMMETRY
AN IMAGINARY LINE THROUGH AN OBJECT SUCH THAT THE OBJECT IS SYMMETRICAL
ABOUT THE LINE
AXISSYMMETRIC OBJECT
AN OBJECT THAT IS SYMMETRIC ABOUT SOME AXIS OR IMAGINARY LINE
A BEAM THAT IS FIXED AT ONE END AND HANGS FREE AT THE OTHER END.
CANTILEVER BRIDGE
CARTESIAN COORDINATES
A REFERENCE OR MEASUREMENT SYSTEM THAT USES THREE FIXED, MUTUALLY
PERPENDICULAR AXES.
CARTESIAN VECTOR NOTATION
CASTIGLIANO'S THEOREM
A MECHANICAL LAW
CENTER OF -GRAVITY, -MASS, -PRESSURE
POINTS OF BALANCE FOR AN OBJECT.
CENTER OF CURVATURE
A POINT THAT MARKS THE CENTER OF A CURVE WITH A CIRCULAR CURVE OR SHAPE
CENTER OF GRAVITY
CENTER OF MASS
CENTER OF MASS
A POINT WHERE THE MASS OF AN OBJECT SEEMS TO BE CONCENTRATED
CENTER OF PERCUSSION
A BALANCE POINT OF AN OBJECT FOR ROTATIONAL MOTION. IT IS THE "SWEET SPOT"
ON A BASEBALL BAT.
CENTIMETER, METER, MILLIMETER, KILOMETER,...
THESE ARE VARIOUS UNITS OF MEASURE.
CENTRAL FORCE
A FORCE THAT PULLS TOWARDS THE SAME POINT. THE SUN'S CENTRAL FORCE
PULLS ON THE EARTH.
CENTRAL FORCE MOTION
MOTION OF AN OBJECT THAT FEELS A FORCE THAT IS ALWAYS PULLING TOWARDS
ONE CENTAL POINT.
CENTRAL IMPACT
A COLLISION IN WHICH THE IMPACTING FORCE LINES UP WITH THE CENTER OF
MASS OF THE OBJECT.
CENTRIPETAL
POINTING TOWARDS THE CENTER
CENTRIPETAL ACCELERATION
A CHANGE IN VELOCITY THAT IS POINTED TOWARDS THE CENTER OF A CIRCLE.
CENTRIPETAL FORCE
CENTROID
A CENTER POINT OF A SHAPE
CENTROID OF THE CROSS-SECTIONAL AREA
A CENTER POINT OF THE AREA SHAPE MADE BY A CROSS SECTIONAL CUT THROUGH
AN OBJECT.
CGS, MKS, SI, ENGLISH,...
DESCRIPTIONS OF DIFFERENT SYSTEMS OF MEASUREMENT UNITS
CHARACTERISTIC EQUATION
A FORMULA DEVELOPED FROM THE ANALYSIS OF A SYSTEM THAT MAY BE SOLVED FOR THE
FREQUENCIES, ENERGIES,... THAT ARE CHARACTERISTIC OF THE SYSTEM AND MAY
BE USED TO CLASSIFY THE SYSTEM BEHAVIOR.
A NUMBER THAT IS USED TO DO CALCULATIONS, OFTEN TO CONVERT ONE KIND OF MEASURE TO ANOTHER.
COEFFICIENT OF DYNAMIC FRICTION
COEFFICIENT OF FRICTION
A PARAMETER (VALUE) THAT IS USED TO CALCULATE THE FORCE OF FRICTION
BETWEEN TWO SURFACES
COEFFICIENT OF RESTITUTION
A PARAMETER (VALUE) THAT IS USED TO CALCULATE THE VELOCITY OF OBJECTS
AFTER THEIR COLLISION
COEFFICIENT OF STATIC FRICTION
COEFFICIENT OF THERMAL EXPANSION
A PARAMETER (VALUE) THAT IS USED TO CALCULATE HOW MATERIALS EXPAND OR
CONTRACT AS THE TEMPERATURE CHANGES.
COFFER DAM
COLLAR BEARINGS
COLLINEAR
ALONG THE SAME LINE
COLUMN WITH PINNED ENDS
A COLUMN WITH ITS ENDS FIXED IN POSITION
COMBINED LOADINGS
OVEALL FORCE OR LOAD ON A STRUCTURAL MEMBER
COMMUTATIVE LAW
COMMUTATIVE PROPERTY
COMPONENT
A PORTION OF A FORCE, VELOCITY,... FOR EXAMPLE, A CAR DRIVING TO THE NORTHEAST HAS A NORTHWARD VELOCITY COMPONENT AND AN EASTWARD VELOCITY COMPONENT.
COMPONENTS
COMPONENTS OF A VECTOR
COMPOSITE
MADE UP OF SEVERAL DISTINCT ELEMENTS OR MATERIALS
COMPOSITE AREAS
AN AREA MADE UP OF SEVERAL BASIC SHAPES
COMPOSITE BEAM
A BEAM MADE UP OF SEVERAL DIFFERENT MATERIALS
COMPOSITE BODIES
COMPRESSIBLE
ABLE TO BE REDUCED IN SIZE ALONG AN AXIS OR DIRECTION
COMPRESSION
COMPRESSION TEST
AN EXPERIMENTAL TRIAL TO DETERMINE THE PROPERTIES OF A MATERIAL UNDER
COMPRESSION.
COMPRESSIVE STRAIN
THE ELONGATION OR CONTRACTION PER UNIT LENGTH OF AN OBJECT WHEN SUBJECTED TO
FORCES.
COMPRESSIVE STRENGTH
COMPRESSIVE STRESSES
FORCES THAT COMPRESS AN OBJECT.
CONCENTRATED LOAD
A LOAD WHICH IS APPLIED AT A POINT OR OVER A SMALL AREA. THE EFFECTS OF
THE FORCE ARE CONCENTRATED AT A POINT AND NOT DISTRIBUTED OVER A SURFACE.
CONCURRENT
CONCURRENT
TENDING TO CONVERGE TO ONE POINT
CONCURRENT FORCE SYSTEMS
CONCURRENT FORCES
CONIC SECTION
A GEOMETRIC SHAPE THAT MATCHES ONE OF THE SHAPES OBTAINED BY A
CROSS SECTION CUT THROUGH A SOLID CONE.
CONSERVATION OF ENERGY
THE ENERGY OF A SYSTEM DOES NOT CHANGE. THE ENERGY AT THE START IS THE
SAME AS THE ENERGY AT THE FINISH.
CONSERVATIVE
SYSTEMS THAT CONSERVE MECHANICAL ENERGY AND DO NOT LOSE ENERGY TO HEAT VIA FRICTION.
CONSERVATIVE FORCES
THESE ARE FORCES THAT DO NOT CAUSE LOSS OF ENERGY TO HEAT. FRICTION IS AN
EXAMPLE OF A NON-CONSERVATIVE FORCE.
CONSTANT
SOMETHING THAT DOES NOT CHANGE FOR THE SYSTEM
CONSTANT COEFFICIENTS
PARAMETERS (VALUES) THAT DO NOT CHANGE AND SOMEHOW DESCRIBE THE
BEHAVIOR OR PROPERTIES OF THE SYSTEM.
CONSTANT OF INTEGRATION
INTEGRATION IS A PROCEDURE OF CALCULUS THAT ADDS UP VALUES AND IT MAY
INVOLVE A CONSTANT VALUE THAT IS RELATED TO THE STARTING OR ENDING
POINT FOR THE ADDITION PROCESS.
CONSTRAINT ON THE SYSTEM
A RULE OR BOUNDARY OR RESTRICTION ON THE MOTION OR BEHAVIOR OF A SYSTEM.
CONSTRAINTS
LIMITATIONS OR RESTRICTIONS ON A SYSTEM
CONSTRAINTS
CONSTRAINTS TO THE MOTION
THE BOUNDARIES OR LIMITATIONS PLACED ON A SYSTEM THAT LIMITS ITS
FREE MOTION.
CONTINUITY CONDITIONS
OFTEN IN JOINING TOGETHER TWO SYSTEMS, THEY MUST MEET A REQUIREMENT
THAT SOME OF THEIR PROPERTIES MUST MATCH AND AGREE ("BE CONTINUOUS")
AT THE BOUNDARY BETWEEN SYSTEMS.
CONTINUOUS BEAMS
SUPPORTING MEMBER THAT HAS NO DISCONTINUITIES (GAPS, ABRUPT TRANSITIONS)
IN ITS CONSTRUCTION.
CONTROL VOLUME
SYSTEMS MAY BE IMAGINED AS POSITIONED WITHIN AN IMAGINARY CONTAINER (THE "CONTROL VOLUME")
SO THAT RESOURCES WHICH FLOW IN AS WELL AS OUT CAN BE ACCURATELY TABULATED.
CONVERSION OF UNITS
COORDINATE AXES
TWO OR THREE INTERSECTING LINES IN SPACE THAT ARE USED AS A MEASUREMENT OR
ANALYTICAL REFERENCE FOR DESCRIBING CALCULATIONS AND SYSTEM COMPONENTS.
COORDINATE SYSTEM
A MEASURING SYSTEM FOR SPECIFYING THE LOCATION OF ANY POINT IN SPACE
FOR DRAWINGS, CALCULATIONS,...
COORDINATE SYSTEM -RECTANGULAR, -POLAR, -SPHERICAL, -CYLINDRICAL
A MEASURING STANDARD OR SYSTEM USED TO SPECIFY THE LOCATION OF POINTS
COORDINATE TRANSFORMATIONS
EQUATIONS THAT ARE USED TO CHANGE FROM ONE SYSTEM OF COORDINATES (MEASUREMENTS)
TO ANOTHER.
COPLANAR
FORCES OR LINES THAT ARE ORIENTED SO THAT THEY BOTH MAY LIE IN THE SAME
SINGLE (IMAGINARY) PLANE (FLAT SURFACE OF INFINITE EXTENSION).
COPLANAR FORCE RESULTANTS
COPLANAR FORCE SYSTEMS
COPLANAR FORCES
CORIOLIS ACCELERATION
THE SIDEWAYS FORCE EXPERIENCED BY OBJECTS AND FLUIDS (AIR, WATER)
MOVING ON THE SURFACE OF A ROTATING SPHERE (LIKE THE EARTH)
COSINE, SINE, TANGENT
MATH FUNCTIONS RELATED TO TRIANGLES USED FOR CALCULATIONS
COUNTERCLOCKWISE
COUPLE
A PAIR OF EQUAL AND OPPOSITE FORCES THAT MAY CAUSE A ROTATION MOTION
CREEP
SLOW DEFORMATION OR MOTION OF A STRUCTURAL MEMBER IN RESPONSE TO FORCES.
CRITICAL LOAD
A LOAD WHICH APPLIES STRESSES AT THE TRANSITION POINT FOR THE STRUCTURE UNDER STUDY.
CRITICALLY DAMPED
APPLYING BARELY SUFFICIENT FRICTION TO AN OSCILLATING SYSTEM TO KEEP IT
FROM OSCILLATING BACK AND FORTH WHEN EXCITED.
CRITICALLY DAMPED MOTION
MOTION OF AN OSCILLATING SYSTEM THAT HAS JUST ENOUGH FRICTION APPLIED
TO PREVENT BACK-AND-FORTH MOTION.
CROSS PRODUCT
A MATHEMATICAL VALUE THAT INVOLVES VECTORS AND USES THE "X" CROSS MULTIPLY
SYMBOL.
CROSS SECTION
AN INTERIOR VIEW OF A CROSS-CUT THROUGH AN OBJECT
CROSS-SECTIONAL AREA
THE AREA OF THE SYRFACE OF A CROSS-CUT THROUGH AN OBJECT.
CURL
CURL OF THE GRADIENT
FINDING THE "CURL" AND "GRADIENT" OF FUNCTIONS ARE MATHEMATICAL PROCEDURES.
CURVILINEAR MOTION
MOTION ALONG A CURVED PATH OR TRAJECTORY - NOT A STRAIGHT LINE.
CURVILINEAR PATH
A CURVED TRAJECTORY OF THE MOTION OF AN OBJECT.
CYCLE
A MOTION OR CHANGE THAT REPEATS IN SPACE OR IN TIME.
CYLINDRICAL COODINATES
THIS IS A MEASURING SYSTEM THAT IS DESIGNED TO MAKE IT EASY TO
DESCRIBE OBJECTS WITH A CYLINDRICAL SHAPE.
THE NATURAL FREQUENCY OFAN OSCILLATING OBJECT THAT EXPERIENCES SOME
FRICTIONAL (DAMPING) FORCE.
DAMPED OSCILLATIONS
OSCILLATIONS OF A VIBRATING (OSCILLATING) SYSTEM THAT ARE AFFECTED
BY FORCES OF FRICTION (DUE TO AIR, FLUIDS, STICKING SURFACES,..)
DAMPING COEFFICIENT
THE PARAMETER (VALUE) THAT SETS THE LEVEL OF FRICTION IN AN OSCILLATING
SYSTEM
DAMPING CONSTANT
THE PARAMETER (VALUE) THAT SETS THE LEVEL OF FRICTION IN AN OSCILLATING
SYSTEM
DAMPING MECHANISMS
THE PHYSICAL CAUSE OF THE FRICTION IN AN OSCILLATING SYSTEM
DEFINITE INTEGRAL
AN INTEGRAL IS FROM CALCULUS AND IT PRESCIBES A WAY TO ADD UP VALUES
OVER CONTINUOUS SURFACES, VOLUMES, REGIONS,... THE DEFINITE INTEGRAL
BEGINS WITH PRESET LIMITS FOR THE ADDITION.
DEFLECTION
A BEND OR CURVING AWAY
DEFLECTION CURVE
A CURVE THAT DEVIATES FROM ITS EXPECTED PATH.
DEFORMABLE
ABLE TO CHANGE SHAPE
DEFORMATION
A CHANGE IN SHAPE
DEGREE OF STATIC INDETERMINACY
THE EXTENT TO WHICH THE FORCES ACTING ON A STRUCTURE CAN BE UNIQUELY
CALCULATED. SOME STRUCTURES ARE SUFFICENTLY COMPLEX THAT APPLICATION
OF THE BASIC LAWS FOR STATIC STRUCTURE SOMETIMES ALLOW MANY AND NO JUST
ONE SINGLE SOLUTION.
DEGREES OF FREEDOM
THE NUMBER OF WAYS OR DIMENSIONS THAT A SYSTEM IS FREE (UNCONSTRAINED)
TO MOVE
DEL OPERATOR
A MATHEMATICAL PROCEDURE INVOLVING CALCULUS AND VECTORS
DENSITY
DERIVATIVE
A PROCEDURE FROM CALCULUS THAT FINDS THE SLOPE OR RATE OF CHANGE
AT ANY POINT ON A CURVE OR SURFACE
DERIVATIVE OF THE STRAIN ENERGY
A PROCEDURE THAT FINDS A CHANGE AMOUNT FOR THE STRAIN ENERGY
DERIVED QUANTITIES
VALUES THAT ARE CALCULATED OR DEDUCED FROM OTHER VALUES
DESIGN STRESS
DETERMINANT
A SQUARE ARRAY ( 2 X 2, 3 X 3, ...) OF NUMBERS IS USED CALCULATE A
SINGLE NUMBER. IT IS USED TO SOLVE GROUPS OF EQUATIONS THAT HAVE TO
SHARE ONE SOLUTION SIMULTANEOUSLY.
DIAGONAL
A LINE CONNECTING OPPOSITE CORNERS IN A SHAPE
DIAMETER
WIDTH OF A CIRCLE
DIFFERENTIAL AREA
DIFFERENTIAL DISK
AN IMAGINARY GEOMETRIC CONSTRUCT WHICH IS A VERY THIN DISK THAT MAY
USED TO CONSTRUCT COMPLEX SHAPES IN LAYERS OF DISKS
DIFFERENTIAL DISPLACEMENT
DIFFERENTIAL ELEMENT
A VERY SMALL ELEMENT OF LENGTH, AREA, MASS, VOLUME, ELECTRIC CHARGE, ...
DIFFERENTIAL EQUATION
AN EQUATION THAT RELATES THE RATES OF CHANGE OF DIFFERENT PROCESSES
OR PHYSICAL PARAMETERS.
DIFFERENTIATION
A MATHEMATICAL PROCEDURE OF CALCULUS FOR TAKING THE DERIVATIVE (FINDING
THE SLOPE) OF A FUNCTION.
DIGITALLY FILTERED
DATA - WHICH MAY BE A PHOTOGRAPH OR NUMERIC VALUES - MAY BE NUMEICALLY
PROCESSED (DIGITALLY FILTERED) TO ENHANCE OR REMOVE SOME FEATURES IN THE
IMAGE OR DATA
DILATATION
THE CHANGE IN VOLUME PER UNIT VOLUME OF AN OBJECT WHEN IT IS SUBJECTED
TO FORCES AND PRESSURES
DIMENSIONAL HOMOGENEITY
DIMENSIONALLY HOMOGENEOUS
DIMENSIONLESS
A NUMBER OR VALUE THAT HAS NO MEASUREMENT UNIT ATTACHED. IT IS INDEPENDENT
OF ANY MEASURING SCALE.
DIMENSIONLESS QUANTITY
A NUMBER OR VALUE THAT HAS NO MEASUREMENT UNIT ATTACHED. IT IS INDEPENDENT
OF ANY MEASURING SCALE.
DIMENSIONS
THE DIMENSIONS OF A NUMBER REFER TO ITS UNITS OF MEASURE.
DIRAC DELTA FUNCTION
A MATHEMATICAL FUNCTION THAT IS ZERO EVERYWHERE EXCEPT AT ONE POINT WHERE
IT HAS AN INFINITE VALUE.
DIRECT PRECESSION
PRECESSION REFERS TO THE ROTATING MOTION THAT THE AXIS OF A SPINNING TOP
UNDERGOES
DIRECTION
DIRECTION COSINES
THE COSINE IS A FUNCTION FROM TRIGONOMETRY THAT MAY BE USED TO SPECIFY
THE ORIENTATION OF A LINE.
DISCRETE
A QUANTITY OR PROPERTY THAT IS COUNTABLE (FINGERS ON A HAND, CARS ON THE ROAD,...)
DISCRETE TIMES
TIMES SEPARATED BY A FIXED (OR AT LEAST) FINITE INTERVAL
DISCRIMINANT
A MATHEMATICAL EQUATION THAT IS SOLVED TO FIND PROPERTIES OF A SYSTEM
DISPLACEMENT
A DISTANCE AND A DIRECTION OF MOTIONDESCRIBING A CHANGE IN POSITION FROM
A STARTING POINT TO A FINAL LOCATION.
DISPLACEMENT-TIME RELATIONSHIP
A GRAPH OR FUNCTION SHOWING HOW THE DISPLACEMENT (POSITION) OF AN OBJECT
CHANGES WITH TIME.
DISSIPATING ENERGY
ENERGY LOST TO HEAT
DISTRIBUTED FORCE
DISTRIBUTED LOAD
A LOAD THAT IS SPREAD OUT OVER THE SURFACE OF A SUPPORTING MEMBER OR
STRUCTURE.
DISTRIBUTED LOADING
DISTRIBUTION
A QUANTITY OR PROPERTY THAT IS SPREAD OUT OVER A REGION
DISTRIBUTIVE LAW
DOT PRODUCT
A MULTIPLICATION PROCESS BETWEEN TWO VECTORS
DOUBLE SHEAR
SHEAR FORCES APPLIED TO TWO SURFACES OF AN OBJECT
DRIVING FORCE
AN EXTERNAL FORCE THAT IS PUSHING ON A SYSTEM
DRIVING FREQUENCY
THE FREQUENCY (TIMES PER SECOND) THAT AN EXTERNAL FORCE ACTS ON A SYSTEM
DRY FRICTION
DUCTILE
A MATERIAL THAT CAN BE SUBJECTED TO LARGE STRAINS BEFORE IT RUPTURES.
DYNAMIC FRICTION
THE FRICTION THAT ACTS WHEN TWO SURFACES MOVE PAST EACH OTHER WHILE IN CONTACT.
A LOAD BEARING DOWN ALONG THE SYMMETRY AXIS OF A COLUMN OR SUPPORTING
MEMBER THAT IS OFF-CENTER
ECCENTRIC IMPACT
AN COLLISION BETWEEN TWO OBJECTS IN WHICH THE IMPACT FORCES DO NOT
LINE UP WITH THE CENTERS OF MASS OF THE COLLIDING OBJECTS
ECCENTRICITY RATIO
A RATIO OF TWO NUMBERS THAT GIVES A MEASURE THE ECCENTRICITY OR ASSYMETRIC
QUALITY OF A SHAPE OR OBJECT.
EFFECTIVE LENGTH
EFFECTIVE LENGTH IS USED TO
DESCRIBE THE FLEXING OF COLUMNS UNDER AXIAL LOADS. THE PERFORMANCE
OF A COLUMN DEPENDS ON WHERE AND HOW THE COLUMN IS SUPPORTED
OR PINNED IN PLACE.
EFFICIENCY
A RATIO OF USEFUL WORK, HEAT OR ENERGY OUTPUT TO THE TOTAL ENERGY USED UP.
THIS RATIO IS A FRACTION LESS THAN 1.
ELASTIC DEFORMATION
ELASTIC DEFORMATION
A CHANGE IN SHAPE OF A BODY THAT IS NOT PERMANENT. THE DEFORMATION
(DENT, STRETCH, COMPRESSION) LASTS ONLY FOR THE DURATION OF THE
IMPACT.
ELASTIC LIMIT
MOST OBJECTS HAVE A LIMITED DEFORMATION RESILIANCY. THE ELASTIC LIMIT
IS THE MAXIMUM STRESS THAT AN OBJECT CAN ENDURE AND STILL RECOVER
ITS SHAPE.
ELASTIC LIMIT
ELASTIC PERFECTLY PLASTIC
ELASTIC SPRING
ELASTIC SUPPORTS
SUPPORTS THAT RECOVER THEIR SHAPE WHEN THE LOAD STRESS IS REMOVED.
ELASTICITY
A MEASURE OF THE ABILITY OF AN OBJECT TO RECOVER ITS SHAPE AFTER AN IMPACT
ELASTOPLASTIC MATERIALS
MATERIALS THAT SHOW SOME ELASTICITY AND SOME PLASTICITY WHEN STRETCHED.
THE MATERIAL DOES NOT RUPTURE WHEN STRESSED BUT ALSO DOES NOT RETURN
TO ITS ORIGINAL SHAPE WHEN THE STRESS IS REMOVED.
ELLIPSE
AN EGG- OR FOOTBALL-SHAPED CURVE
ENERGY
THE ABILITY TO DO WORK. THE ENERGY OF THE UNIVERSE IS CONSERVED: ITS
VALUE STAYS THE SAME OVER TIME.
EQUATION
A MATHEMATICAL EQUALITY RELATING PARAMETERS OR MEASUREMENTS
EQUATIONS OF EQUILIBRIUM
EQUATIONS OF EQUILIBRIUM
THESE ARE FORMULAS INVOLVING BALANCED FORCES AND TORQUES THAT ALLOW
ENGINEERS TO COMPUTE NECESSARY SUPPORTING FORCES SO THAT STRUCTURES
CAN BE DESIGNED TO MATCH THEIR INTENDED APPLICATION.
EQUILATERAL
A SHAPE WITH EQUAL LENGTH SIDES
EQUILIBRIUM
A STEADY-STATE CONDITION IN WHICH FORCES, TORQUES, FLOWS MAY BE HAPPENING
BUT THE SYSTEM UNDER STUDY IS NOT CHANGING WITH TIME.
EQUILIBRIUM
A STATE OF BALANCE. FORCES, MOMENTS, FLOWS MAY BE OCCURRING IN A SYSTEM
BUT NO NET CHANGE IS OCCURRING IN THE SYSTEM.
EQUILIBRIUM EQUATION
THERE ARE TWO KINDS OF EQUILIBRIUM BALANCE SOUGHT FOR STATIC STRUCTURES:
ROTATIONAL AND TRANSLATIONAL EQUILIBRIUM. AN OBJECT IS IN ROTATIONAL
EQUILIBRIUM IF THE SUM OF ALL MOMENTS (TORQUES) ON THE OBJECT EQUALS
ZERO (THE MOMENTS ACT TO CANCEL EACH OTHER). AN OBJECT IS IN TRANSLATIONAL EQUILIBRIUM IF
THE SUM OF ALL FORCES ON THE OBJECT EQUALS ZERO (THE FORCES ACT TO CANCEL
EACH OTHER).
EQUILIBRIUM POSITION
EQUILIBRIUM POSITION
THIS IS THE CONFIGURATION OR POSITION OF AN OBJECT IN WHICH THE
SUM OF MOMENTS (TORQUES) ON AN OBJECT IS ZERO AND THE SUM OF FORCES ON AN
OBJECT IS ZERO. AN OBJECT PLACED AT REST IN ITS EQUILIBRIUM POSITION
OR CONFIGURATION WILL REMAIN IN THAT STATE.
EQUIVALENT COUPLES
ESCAPE VELOCITY
THE MINIMUM SPEED NECESSARY TO COMPLETELY ESCAPE THE GRAVITATIONAL PULL
OF AN OBJECT WITH MASS (PLANET, SUN,...)
EULER BUCKLING
IN 1757, LEONHARD EULER SOLVED A PROBLEM THAT DETERMINED A BUCKLING
LIMIT FOR COLUMN SUPPORTS. COLUMNS THAT FOLLOW EULER'S MODEL OF BUCKLING
ARE EXPERIENCING "EULER BUCKLING".
EULER EQUATIONS OF MOTION
A SET OF THREE DIFFERENTIAL EQUATIONS EXPRESSING RELATIONS BETWEEN
FORCES, MOMENTS, VELOCITIES AND ACCELERATIONS OF A ROTATING, RIGID OBJECT.
EULERIAN ANGLES
THREE ANGLES THAT SPECIFY THE ORIENTATION OF AN OBJECT RELATIVE TO
A REFERENCE AXIS
EXCEEDING THE PROPORTIONAL LIMIT
MANY SYSTEMS RESPOND TO CHANGE IN A PROPORTIONAL MANNER: DOUBLING
THE MAGNITUDE OF ONE KIND OF CHANGE MAY LEAD TO DOUBLING OF A SECOND
KIND OF CHANGE. DOUBLING A TENSION STRESS MAY DOUBLE THE ELONGATION
OF AN OBJECT. THIS PROPORTIONALITY BEHAVIOR IS NORMALLY GOOD ONLY
UP TO SOME LIMIT, BEYOND WHICH BEHASVIORS BECOME MORE COMPLICATED.
EXPRESSION
A MATHEMATICAL STATEMENT OR FORMULA
EXTENSION
EXTENSOMETER
AN INSTRUMENT USED TO MEASURE SMALL CLANGES IN LENGTH
EXTERNAL
COMING FROM OUTSIDE THE SYSTEM UNDER STUDY. IN MANY PROBLEMS, IT IS
IMPORTANT TO KEEP TRACK OF RESOURCES OR FACTORS INSIDE AND OUTSIDE
A SYSTEM BOUNDARY.
REAL-LIFE STRUCTURES NEED TO BE DESIGNED TO SUPPORT FORCES AND MOMENTS
BEYOND EVERY-DAY LOADS. TO ACCOUNT FOR AND SURVIVE UNUSUAL WIND, SNOW,
EARTHQUAKE,... LOADING, STRUCTURES ARE "OVERDESIGNED" TO SUPPORT
FORCES AND MOMENTS THAT EXCEED THE MINIMUMS BY A FACTOR OF SAFETY.
FACTORS
INFLUENCES ON A SYSTEM OR A SERIES OF TERMS THAT ARE PART OF A PRODUCT EXPRESSION
FATIGUE
REPEATED APPLICATION OF A STRESS CAUSES DAMAGE TO A MATERIAL OR STRUCTURAL
MEMBER.
FATIGUE STRENGTH
FILAMENT REINFORCED MATERIAL
A MATERIAL THAT IS REINFORCED (STRENGTHENED) BY INCLUDING A FIBEROUS
SUBSTANCE IN THE MATERIAL
FIRST MOMENT OF AN AREA
FIRST-ORDER DIFFERENTIAL QUANTITY
FIXED END
STRUCTURAL MEMBERS LIKE STRUTS OR COLUMNS MAY HAVE ONE OR BOTH OF THEIR
ENDS FIXED (PINNED) IN POSITION.
FIXED POINT
A POINT THAT IS MAINTAINED AT A SET POSITION.
FIXED-END BEAM
A BEAM WITH BOTH ENDS PINNED OR HELD IN POSITION
FLEXURAL CENTER
BEAMS AND SUPPORTS WILL FLEX (BEND) WHEN STRESSED. THIS CENTER IS
A MIDDLE POINT OF THE CURVE.
FLEXURAL RIGIDITY
THIS IS CONSTANT THAT IS USED TO DESCRIBE THE RIGIDITY OF A BEAM OR BAR.
BEAMS WITH HIGH RIGIDITY REQUIRE A LARGE SIDEWAYS FORCE TO DEFLECT
THE BEAM A UNIT DISTANCE.
FLEXURE FORMULA
AN EQUATION THAT RELATES THE LONGITUDINAL STRESS DISTRIBUTION ON A BEAM TO
THE INTERNAL BENDING MOMENT ACTING ON THE BEAM'S CROSS SECTION.
FLOOR BEAMS
FLUID PRESSURE
FOCI OF AN ELLIPSE
THE SHAPE OF AN ELLIPSE IS BASED ON THE POSITIONING OF TWO POINTS
CALLED THE FOCUS POINTS OF THE SHAPE.
FORCE
A PUSH OR A PULL
FORCE
FORCE-DISPLACEMENT RELATIONS
A GRAPH OR FORMULA THAT SHOWS HOW AN APPLIED FORCE VARIES WITH THE
DISPLACEMENT OF AN OBJECT (A BOWSTRING, FOR EXAMPLE)
FORCED RESPONSE
WHEN AN EXTERNAL FORCE IS APPLIED TO AN OSCILLATING OBJECT, IT WILL
CHANGE ITS MOTION. THIS CHANGE IN MOTION IS THE FORCED RESPONSE
OF THE OSCILLATING OBJECT.
FORCED VIBRATIONS
AN APPLIED EXTERNAL FORCE OR ENERGY SOURCE THAT OSCILLATES OR VARIES PERIODICALLY
IN STRENGTH WILL CAUSE OBJECTS OR SYSTEMS TO OSCILLATE AND UNDERGO
FORCED (AS OPPOSED TO NATURAL, INTERNALLY SUSTAINED) VIBRATIONS.
FORCING FUNCTION
A FUNCTION THAT DESCRIBES HOW A FORCE VARIES IN SPACE AND/OR TIME
FPS
FRACTURE STRESS
THE STRESS LEVEL THAT CAUSES FRACTURE (DESTRUCTION) OF AN OBJECT
FRACTURING
FRAME OF REFERENCE
A MEASURING REFERENCE SYSTEM THAT IS USED TO SPECIFY THE POSITION
OF OBJECTS
FRAMES
FREE BODY DIAGRAM
A DRAWING OF THE OBJECT UNDER STUDY, SHOWING ONLY THE OBJECT AND ALL FORCES APPLIED TO THE OBJECT.
FREE END
AN END OF A STRUCTURAL MEMBER OR BEAM THAT IS FREE TO MOVE IN AT LEAST
ONE DIMENSION.
FREE FALL
THE STATE OF FALLING UNDER THE FORCE OF GRAVITY WITH NO AIR FRICTION IMPEDING
MOTION
FREE RESPONSE
THE UNCONSTRAINED, NATURAL REACTION OF A SYSTEM TO A CHANGE IN ITS
ENVIRONMENT.
FREE VECTOR
FREE VIBRATIONS
UNCONSTRAINED, NATURAL VIBRATIONS OF A SYSTEM OR OBJECT.
FREE-BODY DIAGRAM
A DRAWING OF THE OBJECT UNDER STUDY, SHOWING ONLY THE OBJECT AND ALL FORCES APPLIED TO THE OBJECT.
FREQUENCY
A MEASURE OF HOW MANY TIMES A PHENOMENON REPEATS IN ONE UNIT OF TIME.
DISTANCE BETWEEN PUNCH MARKS ON A MATERIALS OR SPECIMEN BEING TESTED
FOR TENSION AND COMPRESSION BEHAVIOR.
GAUGE PRESSURE
THE AMOUNT OF PRESSURE OVER AND ABOVE ATMOSPHERIC PRESSURE.
GEAR RATIO
A RATIO OF THE NUMBER OF COGS (TEETH) IN TWO GEARS THAT MESH OR ARE
INTERCONNECTED BY A CHAIN.
GENERAL PLANAR MOTION
ANY KIND OF OBJECT MOTION THAT REMAINS WITHIN A FLAT PLANE (OR SURFACE)
GENERAL PLANE MOTION
ANY KIND OF OBJECT MOTION THAT REMAINS WITHIN A FLAT PLANE (OR SURFACE).
THIS IS DESCRIBED AS TWO-DIMENSIONAL MOVEMENT.
GENERAL SOLUTION OF THE DIFFERENTIAL EQUATION
DIFFERENTIAL EQUATIONS ARE FORMULAS THAT RELATE RATES OF CHANGE TO
EACH OTHER. FINDING A SOLUTION TO ONE OR SEVERAL DIFFERENTIAL EQUATIONS
MEANS WORKING BACK TO FIND ALL POSSIBLE FUNCTIONS THAT DO SOLVE
THE DIFFERENTIAL EQUATION. THE MEANING OF "SOLVE" IS THAT THE FUNCTIONS
MUST GIVE AN EQUALITY WHEN SUBSTITUTED BACK INTO THE DIFFERENTIAL
EQUATION.
GENERALIZED HOOKE'S LAW
HOOKE'S LAW STATES THAT STRESS AND ELONGATION OF A MATERIAL ARE PROPORTIONAL.
THE GENERALIZED FORM OF HOOKE'S LAW EXTENDS THE APPLICABILITY OF THE LAW
TO CONDITIONS OF TRIAXIAL STRESS (SUBJECTED TO FORCES IN 3 DIRECTIONS).
GIRDER BRIDGE
GLULAM BEAM
SEVERAL BOARDS GLUE-LAMINATED TOGETHER
GRADIENT
A MATHEMATICAL OPERATION
GRAVITATIONAL ACCELERATION
THE RATE OF CHANGE OF VELOCITY CAUSED BY THE FORCE OF GRAVITY. THE
NEAR-UNIVERSAL SYMBOL FOR THIS CONSTANT IS "G"
GRAVITATIONAL CONSTANT
GRAVITATIONAL CONSTANT
THE CONSTANT THAT APPEARS IN NEWTON'S LAW OF UNIVERSAL GRAVITATION.
IT IS WTITTEN THE SYMBOL "G"
GRAVITATIONAL FORCE
GRAVITY
THE ATTRACTIVE FORCE BETWEEN ANY TWO MASSES
GUSSET PLATE
GUY CABLE
GYROSCOPE
A SPINNING OBJECT THAT SERVES AS AN INSTRUMENT FOR NAVIGATION.
THE SPINNING MOTION AND THE FREE-ROTATING MOUNT OF THE GYROSCOPE
ALLOW THE GYROSCOPE AXIS TO ALWAYS POINT IN THE SAME DIRECTION.
SUBMARINES, SPACECRAFT, AIRPLANES CAN USE THIS REFERENCE TO ACCURATELY
LOG THEIR CHANGES IN DIRECTION WITHOUT ANY EXTERNAL REFERENCE.
AN INFLUENCE THAT INITIATES VIBRATIONS OF A SYSTEM AT ITS NATURAL
FREQUENCY (F) AS WELL AS ITS HIGHER HARMONIC FREQUENCIES (2F, 3F,...)
HEAVISIDE STEP FUNCTION
THIS IS A FUNCTION THAT IS ZERO AT ALL TIMES EXCEPT DURING A SHORT
PERIOD OF TIME WHEN IT BECOMES 1.0. THIS FUNCTION SIMULATES APPLIED
FORCES OR INFLUENCES THAT ACT AS A QUICK IMPULSE.
HOMOGENEOUS
HAVING THE SAME CONSISTENCY OR PROPERTIES THROUGHOUT.
HOMOGENEOUS
SAME COMPOSITION THROUGHOUT
HOMOGENEOUS DIFFERENTIAL EQUATION
A SPECIAL KIND OF DIFFERENTIAL EQUATION WHERE THE SUM OF ALL THE TERMS
INVOLVING RATES IS EQUAL TO ZERO.
HOMOGENEOUS MATERIAL
A MATERIAL THAT HAS THE SAME CONSISTENCY AND PHYSICAL PROPERTIES THROUGHOUT.
HOMOGENEOUS SOLUTION
THIS A MATHEMATICAL SOLUTION TO THE HOMOGENEOUS DIFFERENTIAL EQUATION.
A SECOND MEANING OF THIS TERM COULD BE A LIQUID THAT HAS UNIFORM
CONSISTENCY.
HOOKE'S LAW
A LAW THAT SAYS THAT FORCE AND THE ELONGATION (STRETCH) OF AN OBJECT ARE
PROPORTIONAL TO EACH OTHER.
HORIZONTAL
AT RIGHT ANGLES TO THE UP-DOWN DIRECTION
HORIZONTAL DISPLACEMENT
A VECTOR (ARROW) IN A HORIZONTAL PLANE DRAWN FROM A STARTING POSITION
TO A FINAL POSITION.
HORIZONTAL X-AXIS
A LINE THAT SERVES AS A REFERENCE IN A COORDINATE SYSTEM FOR IDENTIFYING
THE LOCATION OF OBJECTS.
HYBRID STRUCTURAL DESIGN
HYDROSTATIC
CAUSED BY THE PRESSURE OF WATER AT REST
HYDROSTATIC STRESS
PRESSURE (FORCE PER UNIT OF AREA) EXERTED BY WATER
HYPERBOLA
A CURVE SHAPE
HYSTERESIS
FAILURE TO REPEAT THE SAME SERIES OF BEHAVIORS OR MEASUREMENTS
WHEN AN APPLIED FORCE OR EXTERNAL INFLUENCE IS CYCLED THROUGH ITS
RANGE OF VALUES. TYPICALLY, MEASUREMENTS OBTAINED WHILE INCREASING
THE EXTERNAL INFLUENCE ARE NOT THE SAME AS OBTAINED WHEN DECREASING
THE EXTERNAL INFLUENCE.
A BEAM WITH A CROSS SECTION THAT HAS THE SHAPE OF THE CAPITAL LETTER I.
THIS SHAPE IS USED TO PROVIDE RIGIDITY AND REMAIN LIGHTWEIGHT.
IDEAL COLUMN
A COLUMN THAT IS PERFECTLY STRAIGHT BEFORE LOADING.
IDEALIZED MODELS
IDEALIZED STRUCTURE
AN IMAGINED STRUCTURE WITHOUT ANY OF THE IMPERFECTIONS
IJK COMPONENTS
IMPACT
A COLLISION OF SHORT DURATION
IMPENDING
UPCOMING
IMPENDING MOTION
IMPERFECTIONS IN CONSTRUCTION
FLAWS IN WORKMANSHIP OR MATERIALS
IMPULSE
THE PRODUCT OF A FORCE AND THE TIME INTERVAL DURING WHICH IT ACTS.
IMPULSIVE FORCE
A LARGE FORCE OF SHORT DURATION
IN-PLANE PRINCIPAL STRESS
COMPONENTS OF THE PRINCIPAL STRESS THAT LIES IN A SELECTED PLANE
IN-PLANE SHEAR STRESS
COMPONENTS OF THE SHEAR STRESS THAT LIES IN A SELECTED PLANE
INCLINED PLANE
A WEDGE-SHAPED, FLAT SURFACED OBJECT
INCOMPRESSIBLE FLUID
INDEFINITE INTEGRAL
AN INTEGRAL IS A MATHEMATICAL OPERATION THAT ADDS UP THE EFFECTS OF
DISTRIBUTED MASSES AND FORCES. AN INDEFINITE INTEGRAL IS CALCULATED
WITHOUT USING STARTING AND ENDING LIMITS.
INDEPENDENT COORDINATES
INELASTIC BEHAVIOR
WHEN STRESSED TO HIGH ENOUGH LEVELS, A MATERIAL MAY YIELD AND
UNDERGO SOME DEFORMATION THAT IS PERMANENT.
INELASTIC BENDING
BENDING THAT GOES BEYOND THE ELASTIC LIMIT OF THE MATERIAL AND RESULTS
IN SOME PERMANENT DEFORMATION.
INELASTIC BUCKLING
BUCKLING THAT GOES BEYOND THE ELASTIC LIMIT OF THE MATERIAL AND RESULTS
IN SOME PERMANENT DEFORMATION.
INERTIA
A PROPERTY OF A BODY THAT RESISTS ANY CHANGE IN MOTION. FOR TRANSLATION
MOTION, MASS IS A MEASURE OF THE BODY INERTIA. IT IS HARD TO
CHANGE THE STATE OF MOTION OF A HIGH MASS OBJECT. FOR ROTATION, THE
MOMENT OF INERTIA OF A BODY IS A MEASURE OF BODY INERTIA.
INERTIA MATRIX
A 3X3 ARRAY OF NUMBERS THAT CHARACTERIZES THE ROTATIONAL INERTIA
OF AN OBJECT FOR ANY CHOICE OF ROTATIONAL AXIS.
INERTIAL COORDINATE SYSTEM
A COORDINATE OR REFERENCE SYSTEM THAT TRAVELS WITH CONSTANT VELOCITY
INERTIAL COUPLE
A COUPLE THAT ARISES DUE TO THE EFFECTS OF ACCELERATION
INERTIAL FORCE
A FORCE THAT ARISES DUE TO THE EFFECTS OF ACCELERATION
INERTIAL FRAME OF REFERENCE
A MEASUREMENT OR SYSTEM OF REFERENCE THAT TRAVELS AT CONSTANT VELOCITY
INFINITELY LARGE STIFFNESS
A VERY STIFF STRUCTURAL MEMBER OR BEAM
INFINITESMAL
A VERY SMALL BIT OR AMOUNT
INFINITESMAL DISPLACEMENT
A VERY SHORT VECTOR (ARROW) FROM A STARTING POSITION TO NEARBY FINAL
POSITION
INFINITESMAL ROTATION
A VERY SMALL ROTATION OF AN OBJECT THROUGH A TINY ANGLE.
INITIAL CONDITIONS
THE VALUES THAT A SYSTEM HAS AT A STARTING MOMENT
INSTANTANEOUS ACCELERATION
THE ACCELERATION OF AN OBJECT AT AN INSTANT OF TIME
INSTANTANEOUS CENTER
A POINT WHICH IS THE CENTER OF THE OBJECT'S TRAJACTORY AT AN
INSTANT OF TIME.
INSTANTANEOUS VELOCITY
THE VELOCITY OF AN OBJECT AT AN INSTANT OF TIME
INTEGRATING ALONG THE LENGTH
INTEGRATION IS A MATHEMATICAL PROCESS THAT ADDS UP THE EFFECT OF MASSES
AND FORCES DISTRIBUTED OVER AN AREA OR REGION. AN INTEGRATION OVER
A LENGTH DIMENSION OF AN OBJECT ADDS UP THE EFFECT OF THE MATERIAL
OVER THE BEAM LENGTH
INTEGRATION
A MATHEMATICAL PROCEDURE THAT ADDS UP THE EFFECT OF MASSES AND FORCES
THAT ARE DISTRIBUTED OVER AN AREA OR REGION
INTEGRATION
INTERMEDIATE SUPPORTS
STRUCTURAL SUPPORTING MEMBERS IN BETWEEN THE END SUPPORTS
INTERNAL
WITHIN A SYSTEM
INTERNAL FORCES
FORCES THAT ARE EXERTED BETWEEN PARTS OF THE SYSTEM
INTERNAL LOADING
LOADS THAT ARE WITHIN THE OBJECT OR STRUCTURE UNDER STUDY
INTERSECTION
A POINT, LINE OR CURVE WHERE CURVES OR FIGURES CROSS EACH OTHER
INVERSE SQUARE
A VALUE LIKE THE GRAVITY OR ELECTRICAL FORCE THAT DECREASES WITH DISTANCE
INVERSELY AS THE SQUARE OF THE DISTANCE
INWARD BUCKLING
INWARD BENDING OF SUPPORTS OR A WALL
IRREGULAR BOUNDARIES
A BOUNDARY MADE UP OF UNUSUAL SHAPES AND FORMS, NOT PATTERNED AFTER SIMPLE
GEOMETRIC SHAPES OR FORMS.
ISOTROPIC
A MATERIAL OR ENVIRONMENT THAT HAS SIMILAR PROPERTIES IN ALL DIRECTIONS
ISOTROPIC MATERIAL
A MATERIAL THAT HAS THE SAME PHYSICAL PROPERTIES IN ALL DIRECTIONS. A
MATERIAL THAT HAS NO PREFERRED OR SPECIAL DIRECTION.
THE SIDE-TO-SIDE DEFLECTION OF A BEAM WHEN SUBJECTED TO A SIDEWAYS FORCE
LIMIT MOMENT
LINE OF ACTION
A LINE DRAWN PARALLEL TO THE DIRECTION OF AN APPLIED FORCE
LINEAR
PROPERTY OF SYSTEMS WHERE THE SYSTEM OUTPUT OR RESPONSE IS IN DIRECT
PROPORTION TO THE INPUT. DOUBLING THE INPUT (LOAD, FORCE, ENERGY, TENSION,...)
HAS THE EFFECT OF DOUBLING THE OUTPUT (STRETCH, COMPRESSION, DISPLACEMENT,...)
LINEAR COEFFICIENT OF THERMAL EXPANSION
A VALUE THAT IS USED TO CALCULATE THE AMOUNT BY WHICH A MATERIAL EXPANDS
OR CONTRACTS WHEN HEATED OR COOLED.
LINEAR ELASTIC SPRING
LINEAR IMPULSE
A FORCE APPLIED OVER A SHORT TIME THAT CAUSES TRANSLATIONAL MOTION OF
AN OBJECT.
LINEAR MOMENTUM
THIS IS A PRODUCT OF THE MASS AND VELOCITY OF A BODY (M*V) WHICH IS
CONSERVED (PRESERVED) IN COLLISIONS AND INTERACTIONS AS LONG AS THE
EXTERNALLY APPLIED FORCE ON THE SYSTEM IS ZERO.
LINEAR SPRING
A SPRING WHICH DOUBLES ITS STRETCH (OR COMPRESSION) WHEN THE APPLIED
FORCE IS DOUBLED.
LINEAR VARIATION
A CHANGE IN PARAMETERS THAT FOLLOWS A DIRECTLY PROPORTIONAL RELATION.
LINEAR VARIATIONS ARE DEMONSTRATED BY SHOWING THAT THE DATA FOLLOW A
STRAIGHT LINE GRAPH.
LINEAR VELOCITY
A RATE OF CHANGE OF POSITION WITH TIME FOR TRANSLATIONAL MOTION. VELOCITY
INCLUDES THE NOTION OF BOTH SPEED AND THE DIRECTION OF MOTION.
LINEAR/ANGULAR IMPULSE
A FORCE/MOMENT THAT ACTS OVER A SHORT TIME TO CAUSE A CHANGE IN
TRANSLATION/ROTATION MOTION.
LINEAR/ANGULAR MOMENTUM
THIS IS A PRODUCT OF INERTIA*VELOCITY FOR TRANSLATION/ROTATION
MOTION.
LINEARLY DISTRIBUTED FORCE
LINEARLY ELASTIC
A MATERIAL THAT DEFORMS PROPORTIONATELY TO THE APPLIED STRESS AND
RETURNS TO ITS ORIGINAL SHAPE WHEN THE STRESS IS REMOVED.
LINEARLY VARYING LOAD
A LOAD THAT VARIES PROPORTIONALLY TO SOME OTHER SYSTEM PARAMETER.
LINERALY ELASTIC
LOAD
A FORCE WHICH REPRESENTS THE BURDEN THAT MUST BE SUPPORTED BY A STRUCTURE
LOAD CELL
LOAD INTENSITY
LOAD PER SQUARE AREA
LOAD-DEFORMATION CURVE
LOAD-INTENSITY DIAGRAM
LOADING FUNCTION
LOCAL BUCKLING
BUCKLING THAT MIGHT OCCUR IN A OVERSTRESSED PORTION OF A COMPOSITE
STRUCTURE
LOGARITHMIC DECREMENT
A WAY OF REDUCING PARAMETERS BY DECREMENTS OF POWERS OF 10 (1000, 100, 10,...)
AND NOT OF A FIXED INTERVAL (1000, 900, 800,,...)
LONGITUDINAL SHEAR-STRESS
A STRESS IN WHICH THE MATERIAL ON ONE SIDE OF A LONGITUDINAL BEAM PUSHES ON THE
MATERIAL ON THE OTHER SIDE OF THE LONGITUDINAL BEAM WITH A FORCE PARALLEL TO
THE SURFACE AND ACTING ALONG THE LONGITUDINAL PLANES OF THE BEAM.
LONGITUDINAL STRAIN
ELONGATION OR CONTRACTION THAT OCCURS ALONG THE LONGITUDINAL DIMENSION OF
A BEAM OR SUPPORT.
A VALUE WHICH MEASURES THE STRENGTH OR SIZE OF A PARAMETER. THE MAGNITUDE
IS A SINGLE, POSITIVE NUMBER.
MAGNITUDE OF THE VECTOR
A VECTOR IS A LINE SEGMENT WITH A DIRECTION (AN ARROW). THE MAGNITUDE
OF THE VECTOR IS ITS LENGTH.
MARGIN OF SAFETY
A FACTOR BY WHICH THE LOAD ON A STRUCTURE MAY BE INCREASED ABOVE NORMAL
WITHOUT CAUSING BUILDING OR STRUCTURE FAILURE.
MASS
THE RESISTANCE OF AN OBJECT TO A CHANGE IN TRANSLATIONAL MOTION
MATRIX
A RECTANGULARLY SHAPED ARRAY OF NUMBERS USED FOR SIMPLIFYING THE
MANIPULATION OF COMPLEX EQUATIONS.
MATRIX EQUATION
AN EQUATION THAT RELATES VALUES IN RECTANGULARLY SHAPED ARRAYS.
MAXIMUM NORMAL STRESS THEORY
NORMAL STRESS IS THE FORCE PER AREA (OR FORCE INTENSITY) APPLIED
PERPENDICULAR (NORMAL) TO AN AREA.
MAXIMUM SHEAR-STRESS THEORY
SHEAR STRESS IS CAUSED BY A FORCE APPLIED PARALLEL (SHEAR) TO A SURFACE
MECHANICAL EFFICIENCY
A RATIO OF USEFUL WORK OUTPUT TO TOTAL ENERGY INPUT. THIS IS A
VALUE LESS THAN 1.0.
MECHANICS
THE STUDY OF FORCE, ENERGY AND THE MOTION OF MASSES
MEDIAN LINE
CENTRAL LINE THAT DIVIDES A SURFACE INTO TWO EQUAL PARTS
METHOD OF JOINTS
METHOD OF SECTIONS
METHOD OF SUPERPOSITION
AN ANALYSIS TECHNIQUE THAT ALLOWS COMPLEX PROBLEMS TO BE SOLVED BY
COMBINING (SUPERPOSITIONING) THE SOLUTIONS TO OTHER SIMPLER COMPONENT
PROBLEMS.
MODULUS OF ELASTICITY
A CONSTANT FOR A SPRING OR ELASTIC OBJECT THAT IS A RATIO OF THE
FORCE APPLIED AND THE SPRING ELONGATION (OR OBJECT ELASTIC DEFORMATION)
MODULUS OF RESILIENCE
THIS IS A CONSTANT FOR A MATERIAL THAT REPRESENTS THE ABILITY OF THE MATERIAL TO ABSORB
ENERGY WITHOUT ANY PERMANENT DAMAGE TO THE MATERIAL.
MODULUS OF RIGIDITY
A RATIO OF A SHEAR FORCE TO THE SHEAR STRAIN CAUSED BY THE FORCE. THIS IS ALSO
CALLED THE SHEAR MODULUS OF ELASTICITY.
MODULUS OF TOUGHNESS
THIS IS A CONSTANT FOR A MATERIAL THAT REPRESENTS THE STRAIN ENERGY DENSITY OF
A MATERIAL JUST BEFORE IT FRACTURES.
MOHR'S CIRCLE
A VISUAL TECHNIQUE FOR ANALYZING PLANE STRESS AND STRAIN.
MOMENT
A FORCE APPLIED TO AN OBJECT AT SOME DISTANCE FROM THE ROTATION AXIS THAT
MAY CAUSE THE OBJECT TO ROTATE. THIS IS THE SAME AS A TORQUE. THE MOMENT
IS CALCULATED AS THE PRODUCT OF A FORCE TIMES THE DIRSTANCE OF ITS
POINT OF APPLICATION FROM THE AXIS OF ROTATION.
MOMENT ARM
MOMENT DIAGRAM
A SKETCH OF THE MOMENTS APPLIED TO AN OBJECT
MOMENT OF A COUPLE
MOMENT OF A FORCE ABOUT AN AXIS
MOMENT OF INERTIA
THE RESISTANCE OF A BODY TO ANY CHANGE IN ROTATIONAL MOTION. THIS IS
CALCULATED AS A PRODUCT OF MASS TIMES THE SQUARE OF THE DISTANCE FROM
THE MASS TO THE AXIS.
MOMENT-AREA METHOD
A SEMIGRAPHICAL METHOD FOR FINDING THE SLOPE AND DISPLACEMENT OF POINTS
ON THE ELASTIC CURVE OF A BEAM OR STRUCTURAL MEMBER.
MOMENT-CURVATURE EQUATION
THE RELATION BETWEEN THE INTERNAL MOMENTS IN A BEAM AND THE RADIUS
OF CURVATURE OF THE BEAM.
THE NUMBER OF OSCILLATIONS PER UNIT OF TIME THAT AN OBJECT COMPLETES
WHEN LEFT TO OSCILLATE NATURALLY WITH PERIODIC DRIVING FORCES.
NECK
NECKING
AT THE ULTIMATE STRESS, THE CROSS SECTIONAL AREA OF A MEMBER BEGINS
TO DECREASE AT A LOCALIZED REGION.
NEUTRAL AXIS
IN A BENT BEAM, IT IS THE LINE OF ZERO STRESS BELOW WHICH ALL FIBERS
ARE IN TENSION AND ABOVE WHICH THEY ARE IN COMPRESSION.
NEUTRAL EQUILIBRIUM
EQUILIBRIUM IS NEUTRAL EQUILIBRIUM WHEN THE SYSTEM DOES NOT DEPART FROM ITS
POSITION OF EQUILIBRIUM. A BALL ON A FLAT SURFACE IS IN NEUTRAL EQUILIBRIUM.
NEUTRAL SURFACE
A SURFACE IN A BENT BEAM ALONG WHICH THE BEAM MATERIAL IS NEITHER
COMPRESSED NOR EXTENDED.
NEWTON
NEWTON
A SCIENTIST/MATHEMATICIAN WHO DEVELOPED THREE LAWS OF MOTION AND THE LAW
OF UNIVERSAL GRAVITATION THAT ARE USED TODAY.
NEWTON'S LAW OF GRAVITATIONAL ATTRACTION
NEWTON'S LAWS OF MOTION
NEWTON'S SECOND LAW
THIS LAW RELATES FORCE (F), MASS (M) AND ACCELERATION (A): F = MA.
NEWTON'S THREE LAWS OF MOTION
NOMINAL OR ENGINEERING STRAIN
THE AMOUNT OF STRAIN EXPECTED BY A STRUCTURAL MEMBER UNDER NORMAL
(NOMINAL) LOADING CONDITIONS.
NOMINAL STRESS
NON-CONCURRENT
NON-COPLANAR
NONCONSERVATIVE FORCE
NONLINEAR
A SYSTEM THAT DOES NOT FOLLOW THE LAW OF SUPERPOSITION. SUPERPOSITION
IS TRUE IF YOU CAN MODEL THE COMPLEX SITUATION AS COMPOSED OF SIMPLER,
BASIC SYSTEM. SUPPOSE A CAUSES B TO HAPPEN AND C CAUSES D TO HAPPEN.
WHAT WILL OCCUR IF WE DO (A+C)? IN A NONLINEAR SYSTEM, (B+D) WILL NOT
BE ALL OF THE OUTCOME.
NONLINEAR EQUATION
A EQUATION THAT DOES NOT FOLLOW THE LAW OF SUPERPOSITION. SUPERPOSITION
IS TRUE IF YOU CAN MODEL THE COMPLEX SITUATION AS COMPOSED OF SIMPLER,
BASIC SYSTEM. SUPPOSE A SOLVES EQUATION B AND C SOLVES EQUATION D.
WHAT WILL OCCUR IF WE HAVE EQUATION (B+D)? IN A NONLINEAR SYSTEM, (A+C)
WILL NOT BE ALL OF THE SOLUTION.
NONORTHOGONAL COMPONENTS
VECTOR VALUES (WHICH HAVE A MAGNITUDE AS WELL AS A DIRECTION)
CAN BE DIVIDED UP INTO PARTS (COMPONENTS) THAT POINT IN SPECIFIC,
STANDARD DIRECTIONS. MOST OF THE TIME, THESE STANDARD DIRECTIONS
ARE CHOSEN TO BE MUTUALLY PERPENDICULAR (AT 90O, ORTHOGONAL)
TO EACH OTHER. AT TIMES, THESE DIRECTIONS ARE CHOSEN IN
NONPERPENDICULAR AND THE COMPONENTS ARE CALLED NONORTHOGONAL
COMPONENTS.
NONPRISMATIC BEAM
A BEAM WITH A VARIABLE CROSS SECTIONAL AREA (I.E. A BEAM VARIES BETWEEN
"FAT" AND "SKINNY")
NONRIGID
NONUNIFORM
VARIABLE IN SPACE OR TIME.
NONUNIFORM BENDING
A BEAM THAT BENDS DIFFERENT AMOUNTS DEPENDING ON LOCATION.
NONUNIFORM TORSION
A BEAM THAT EXPERIENCES DIFFERENT TWISTING MOMENTS DEPENDING ON LOCATION.
NORMAL
IN MECHANICS, NORMAL OFTEN MEANS PERPENDICULAR OR AT RIGHT ANGLES TO
A SURFACE OR A DIRECTION. NORMAL CAN ALSO MEAN NOMINAL OR AVERAGE.
NORMAL ACCELERATION
AN ACCELERATION THAT IS PERPENDICULAR TO THE DIRECTION OF MOTION.
NORMAL COMPONENTS
VECTOR VALUES (WHICH HAVE A MAGNITUDE AS WELL AS A DIRECTION)
CAN BE DIVIDED UP INTO PARTS (COMPONENTS) THAT POINT IN SPECIFIC,
STANDARD DIRECTIONS. MOST OF THE TIME, THESE STANDARD DIRECTIONS
ARE CHOSEN TO BE MUTUALLY PERPENDICULAR (AT 90O, NORMAL, ORTHOGONAL)
TO EACH OTHER.
NORMAL COORDINATES
COORDINATES ARE NUMBERS THAT MAY BE USED TO SPECIFY THE POSITION
OF A POINT IN SPACE. OFTEN THESE COORDINATE NUMBERS ARE MEASURED
WITH REFERENCE TO A LINE DRAWN IN SPACE. OFTEN THESE LINES INTERSECT
AT ONE POINT CALLED THE ORIGIN AND ARE MUTUALLY PERPENDICULAR (NORMAL)
TO EACH OTHER.
NORMAL FORCE
A FORCE THAT IS PERPENDICULAR TO A SURFACE OR THE DIRECTION OF MOTION
OF A SYSTEM.
NORMAL STRAIN
A COMPONENT OF THE STRAIN THAT IS PERPENDICULAR (NORMAL) TO A PLANE OF REFERENCE
NORMAL STRESS
A COMPONENT OF THE STRESS THAT IS PERPENDICULAR (NORMAL) TO A PLANE OF REFERENCE
NORMAL STRESS COMPONENTS
COMPONENTS OF THE STRESS THAT ARE PERPENDICULAR (NORMAL) TO A PLANE OF REFERENCE
NUMERICALLY DIFFERENTIATE
EVALUATES THE VALUE OF A FUNCTION OR DATA AT NEARBY POINTS AND ESTIMATES THE VALUE
OF THE DERIVATIVE (SLOPE) IN THE VICINITY.
NUTATION
A BOBBING OR NODDING MOTION THAT A SPINNING RIGID BODY (LIKE A TOP)
MIGHT UNDERGO.
NUTATION ANGLE
AN ANGLE ASSOCIATED WITH THE NUTATION MOTION OF A SPINNING RIGID BODY.
A REFERENCE SYSTEM FOR THREE DIMENSIONAL SPACE USES THREE MUTUALLY
PERPENDICULAR LINES FOR AXES THAT INTERSECT AT ONE POINT. THESE
THREE INTERSECTING LINES DIVIDE ALL OF SPACE INTO 8 REGIONS, CALLED
OCTANTS.
ON THE VERGE OF SLIDING
ONE DEGREE OF FREEDOM
THE MOTION OF AN OBJECT WITH ONE DEGREE OF FREEDOM CAN BE COMPLETELY DESCRIBED
WITH ONE POSITION COORDINATE. OFTEN, SYSTEMS WITH ONE DEGREE OF FREEDOM
ARE CAPABLE OF ONLY STRAIGHT LINE MOTION.
OPERATION
A MATHEMATICAL PROCEDURE OF SOME KIND
OPTIMIZATION
A PROCEDURE THAT TRIES TO MAXIMIZE OR MINIMIZE SOME VALUE OR QUALITY
OF A SYSTEM.
ORBITAL MECHANICS
THE DESCRIPTION OF MOTION OF OBJECTS THAT MUTUALLY ATTRACT AND MOVE AROUND
EACH OTHER (LIKE THE SUN AND PLANET SYSTEM).
ORDINARY DIFFERENTIAL EQUATION
A CERTAIN KIND OF EQUATION THAT RELATES RATES OF CHANGE FOR A SYSTEM TO
EACH OTHER.
ORIENTED ALONG THE AXIS
POINTED ALONG ONE OF THE COORDINATE OR ROTATIONAL AXIS DIRECTIONS
ORIGIN
THE REFERENCE POINT ESTABLISHED FOR POSITIONING A COORDINATE SYSTEM
FOR SPECIFYING THE LOCATION OF POINTS IN SPACE.
ORTHOGONAL
PERPENDICULAR OR NORMAL
ORTHOGONAL AXES
REFERENCE LINES THAT ARE MUTUALLY PERPENDICULAR
ORTHOGONAL CURVILINEAR COORDINATES
PERPENDICULAR COORDINATE AXES THAT ARE ADAPTED TO EASILY DESCRIBE MOTION
ON CURVED (CYLINDRICAL, SPHERICAL,...) PATHS, SURFACES AND VOLUMES.
ORTHOGONAL TRANSFORMATION MATRIX
AN ARRAY OF NUMBERS USED TO TRANSFORM VALUES BETWEEN DIFFERENT MEASURING
AND COORDINATE SYSTEMS.
ORTHOTROPIC
HAVING ELASTIC PROPERTIES WITH CONSIDERABLE VARIATIONS IN STRENGTH
IN DIFFERENT DIRECTIONS.
OSCULATING PLANE
OVERALL BUCKLING
OVERDAMPED MOTION
MOTION OF AN OSCILLATING OBJECT WHEN THE FRICTION OF MOTION IS SO HIGH
AS TO SLOW THE MOTION DOWN TO A SLOW APPROACH TO EQUILIBRIUM WITH
NO OSCILLATIONS.
A CURVE THAT IS THE SAME AS THE PATH OF A PROJECTILE
LAUNCHED UNDER THE INFLUENCE OF GRAVITY NEAR THE SURFACE OF THE EARTH.
PARALLEL
PARALLEL AXIS THEOREM
A HANDY RESULT THAT HELPS CALCULATE THE MOMENT OF INERTIA FOR A RIGID
OBJECT AROUND ANY AXIS ONCE YOU KNOW THE MOMENT OF INERTIA OF THE OBJECT
AROUND ONE AXIS. THE AXES USED MUST BE PARALLEL TO EACH OTHER.
PARTIAL DERIVATIVE
A DERIVATIVE THAT TELLS YOU HOW MUCH A FUNCTION CHANGES WHEN ONLY ONE
OF THE FUNCTION PARAMETERS CHANGES. THE "PARTIAL" LABEL IS USED
BECAUSE ONLY ONE OF THE PARAMETERS MAY CHANGE AT A TIME.
PARTIAL DIFFERENTIAL EQUATION (PDE)
AN EQUATION RELATING RATES OF CHANGE FOR INDIVIDUAL PARAMETERS
IN A SYSTEM. CONSIDERABLE WORK CAN BE DONE TO SOLVE THESE EQUATIONS.
SOLVING A PARTIAL DIFFERENTIAL EQUATION MEANS FINDING ALL THE FUNCTIONS
THAT SATISFY THE RATE RELATIONS GIVEN IN THE PDE.
PARTICLE
AN OBJECT WITH VERY SMALL DIMENSIONS COMPARED TO ANY OTHER SYSTEM
PARAMETER. ONE CAN THINK OF A PARTICLE AS LOCATED AT A POINT IN
SPACE AND IGNORE ANY EFFECTS CAUSED BY THE FINITE SIZE OF THE OBJECT.
PARTICULAR SOLUTION
A PART OF A SOLUTION TO A DIFFERENTIAL EQUATION
PENDULUM
AN OBJECT ATTACHED BY A LIGHT WIRE OR STRING TO A SUPPORT THAT SWINGS
BACK AND FORTH UNDER THE PULL OF GRAVITY.
PERCENT ELONGATION
THE PERCENT CHANGE IN LENGTH THAT AN OBJECT UNDERGOES WHEN LONGITUDINAL
STRESS IS APPLIED THE THE OBJECT OR THE TEMPERATURE OF THE OBJECT CHANGES.
PERCENT ELONGATION
PERCENT REDUCTION IN AREA
PERFECTLY ALIGNED
USED WITH REFERENCE TO LOADS OR FORCES THAT LINE UP CENTERED ON
A SUPPORTING MEMBER OR COLUMN.
PERFECTLY FLEXIBLE
PERFECTLY PLASTIC
BEYOND THEIR ELASTIC LIMIT, PERFECTLY PLASTIC MATERIALS WILL CONTINUE TO ELONGATE
(STRETCH) EVEN WHEN THE LOAD IS KEPT CONSTANT.
PERFECTLY PLASTIC IMPACT
A COLLISION IN WHICH THE COLLIDING OBJECTS UNDERGO A PERMANENT CHANGE
IN SHAPE
PERIGEE
MINIMUM DISTANCE FROM A SATELLITE IN ORBIT TO THE CENTER OF THE EARTH
OR OTHER ATTRACTING OBJECT.
PERIOD
TIME FOR ONE COMPLETE ORBIT, CYCLE OR OSCILLATION OF A SYSTEM TO BE
COMPLETED.
PERIOD OF DEFORMATION
DURING A COLLISION, THIS IS THE TIME WHILE THE COLLIDING SURFACES
ARE APPROACHING EACH OTHER AND ARE BEING DEFORMED.
PERIOD OF RESTITUTION
DURING A COLLISION, THIS IS THE TIME WHILE THE COLLIDING SURFACES
SEPARATE FROM EACH OTHER AND RETURN TO THEIR ORIGINAL SHAPE OR REMAIN
PERMANETELY DEFORMED.
PERMANENT SET
PERMANENT PLASTIC DEFORMATION OF AN OBJECT AFTER THE APPLIED LOAD IS
REMOVED.
PERMANENT STRAIN
A PERMANENT CHANGE IN LENGTH OR DIMENSION DUE TO AN APPLIED LOAD
PERPENDICULAR
PERPENDICULAR, MUTUALLY
USED TO DESCRIBE LINES THAT ARE ORIENTED TO BE AT RIGHT ANGLES (90O)
TO EACH OTHER.
PHASE
THIS WORD HAS MULTIPLE MEANINGS. SOLID, LIQUID AND GAS ARE THREE PHASES OF MATTER.
CONCERNING OSCILLATING OR ROTATING OBJECTS, THE PHASE IS THE ANGULAR MEASURE
(IN DEGREES OR RADIANS) OF THE LEAD AHEAD OR LAG BEHIND THAT AN OBJECT HAS
WHEN IN MOTION.
PHYSICAL SIGNIFICANCE
AN INTERPRETATION THAT ATTEMPTS TO EXPLAIN AND CLARIFY THE IMPORTANCE OF
SOME PHENOMENA BEYOND THE MATHEMATICAL EQUATIONS.
PIER
PIN SUPPORT
A BOLT OR PIN THAT TYPICALLY IS REMOVABLE AND SERVES AS A HINGE FOR A SUPPORT
MEMBER.
PIVOT BEARINGS
PLANAR MOTION
MOTION OF AN OBJECT WHERE THE CENTER OF MASS OF THE OBJECT REMAINS
IN A SINGLE (UNCHANGING) PLANE (IMAGINARY FLAT SURFACE).
PLANAR TRUSSES
PLANE
NORMALLY A FLAT, IMAGINARY SURFACE
PLANE MOTION
MOTION OF AN OBJECT WHERE THE CENTER OF MASS OF THE OBJECT REMAINS
IN A SINGLE (UNCHANGING) PLANE (IMAGINARY FLAT SURFACE).
PLANE OF BENDING
A PLANE ORIENTED TO INCLUDE THE BENDING CURVE OF A COLUMN OR SUPPORTING MEMBER
PLANE OF MOTION
A PLANE WHICH INCLUDES THE PATH OR TRAJACTORY OF THE CENTER OF MASS OF A
MOVING OBJECT.
PLANE OF THE MOTION
A PLANE WHICH INCLUDES THE PATH OR TRAJACTORY OF THE CENTER OF MASS OF A
MOVING OBJECT.
PLANE STRAIN
A DEFORMATION OF AN OBJECT IN WHICH ALL THE DISPLACEMENTS OF THE PARTS
OF THE OBJECT ARE PARALLEL TO A SINGLE PLANE (OR FLAT SURFACE)
PLANE STRESS
A STATE OF STRESS IN WHICH THE STRESSES REMAIN PARALLEL TO A SINGLE PLANE.
PLASTIC DEFORMATION
PLASTIC DEFORMATION
A PERMANENT DEFORMATION (IN SHAPE OR SIZE) THAT REMAINS AFTER THE APPLIED FORCE OR LOAD IS REMOVED.
PLASTIC HINGE
PLASTIC REGIME
PLASTICITY
THE PROPERTY OF A MATERIAL WHEREBY IT EXPERIENCES PERMANENT DEFORMATION
WHEN SUBJECTED TO STRESS EXCEEDING THE YIELD LIMIT OF THE MATERIAL.
PLATE GIRDER
A RIVETED OR WELDED STEEL GIRDER
POINT
A POSITION OR LOCATION IN SPACE
POISSON'S RATIO
THE RATIO OF THE TRANSVERSE CONTRACTING STRAIN (GIRTH OF THE OBJECT)
TO THE ELONGATION STRAIN (STRETCH OF THE OBJECT) WHEN STRETCHED
BY FORCES APPLIED TO THE ENDS OF THE OBJECT AND PARALLEL TO THE
LONGITUDINAL AXIS OF THE OBJECT. THIS RATIO MEASURES PROPORTIONATELY
HOW MUCH A MATERIAL "NECKS DOWN" WHEN IT IS STRETCHED.
POLAR COORDINATES
A TWO DIMENSIONAL COORDINATE SYSTEM THAT USES A RADIUS AND AN ANGLE TO SPECIFY THE
POSITION OF POINTS (INSTEAD OF X AND Y COORDINATE VALUES).
POLAR MOMENT OF INERTIA
POLYGON
A CLOSED SHAPE WHOSE SIDES ARE FORMED WITH MANY STRAIGHT-LINE SEGMENTS
POSITION
A POINT IN SPACE. COORDINATES ARE THE NUMBERS USED TO SPECIFY
THE POSITION OF THE POINT IN SPACE.
POSITION VECTOR
POSITION VECTOR
A STRAIGHT, DIRECTED LINE SEGMENT (ARROW) FROM THE ORIGIN TO THE
A PARTICLE OR A ARBITRARY POINT IN SPACE.
POTENTIAL ENERGY
POTENTIAL ENERGY
A FORM OF ENERGY WHERE THE ENERGY IS STORED IN A MANNER THAT CAN BE
RELEASED OR CONVERTED TO ENERGY OF MOVEMENT (KINETIC ENERGY) TO DO WORK.
POWER
THIS IS THE RATE OF USING ENERGY (ENERGY USED PER UNIT OF TIME). IT IS
COMMONLY MEASURED IN WATTS AND HORSEPOWER.
POWER TRANSMISSION
A SEQUENCE OF GEARS OR LINKAGES THAT TRANSMIT POWER FROM A MOTOR
OR ENGINE TO A SECONDARY SYSTEM OF MOVING PARTS (WHEELS ON A CAR, FOR EXAMPLE).
THE TRANSMISSION IS OFTEN NEEDED TO ADAPT THE ENGINE CHARACTERISTICS, PERFORMANCE,
AND EFFICIENT USE TO THE VARYING DEMANDS AND LOADS PUT ON THE ENGINE.
PRECESSION
THE MOTION OF SPINNING OF A TOP MAY BE DESCRIBED WITH THREE ANGULAR
VELOCITIES: PRECESSION, NUTATION AND SPIN. PRECESSION IS THE SLOW CIRCULAR
MOTION MADE THE TOP AXIS.
PRECESSION ANGLE
AN ANGLE DESCRIBING THE POSITION OF A SPINNING RIGID BODY (A GYROSCOPE).
THIS ANGLE MEASURES HOW FAR THE AXIS OF SPIN OF THE BODY
HAS ROTATED AS MEASURED IN A HORIZONTAL PLANE.
PREFIXES
PRESSURE
THE FORCE OR LOAD PER UNIT OF AREA.
PRESSURE DISTRIBUTION
PRESSURE VESSELS
CLOSED CONTAINERS THAT MUST BEAR THE LOAD OF A FLUID FROM THE INSIDE
AND/OR THE OUTSIDE.
PRINCIPAL AXES
THREE SPECIAL AXES OF SYMMETRY OF AN OBJECT USED FOR PREDICTING THE
ROTATIONAL BEHAVIOR OF THE OBJECT.
PRINCIPAL AXES OF INERTIA
AXES OR DIRECTED LINES NORMALLY CORRESPOND TO THE AXES OF SYMMETRY OF
AN OBJECT. THE ORIENTATION OF THESE AXES MAY BE DETERMINED BY
MATHEMATICAL PROCEDURES.
PRINCIPAL MOMENTS OF INERTIA
THESE SPECIFY THE RESISTANCE OF AN OBJECT TO A CHANGE IN ROTATIONAL MOTION
WHEN THE PRINCIPAL AXES OF INERTIA ARE USED AS THE REFERENCE AXES.
PRINCIPAL STRAIN
THE ELONGATION OR COMPRESSION OF THE OBJECT ALONG ONE OF THE
PRINCIPAL AXES OF STRAIN OF THE OBJECT.
PRINCIPAL STRESS
A STRESS OCCURRING AT RIGHT ANGLES TO THE PRINCIPAL PLANE OF STRESS
PRINCIPLE OF CONSERVATION OF LINEAR/ANGULAR MOMENTUM
A LAW WHICH STATES THAT THE AMOUNT OF LINEAR [ANGULAR] MOMENTUM OF A OBJECT
STAYS THE SAME (DOES NOT CHANGE) IF THE NET EXTERNAL FORCE [MOMENT] ON THE
SYSTEM IS ZERO.
PRINCIPLE OF SUPERPOSITION
A LAW WHICH IS FOLLOWED BY "LINEAR" SYSTEMS. THIS PRINCIPLE IS USED
IN MANY FIELDS OF SCIENCE AND ENGINEERING. OFTEN, COMPLEX PROBLEMS
CAN BE DECOMPOSED INTO SEVERAL SIMPLER, SOLVABLE PROBLEMS. IF THE
SOLUTION TO THE COMPLEX PROBLEM CAN BE EXPRESSED AS A SIMPLE SUM
OR SUPERPOSITION OF THE SIMPLE PROBLEM SOLUTIONS, THEN THE UNDERLYING
PHENOMENA FOLLOWS THE PRINCIPLE OF SUPERPOSITION.
PRINCIPLE OF TRANSMISSIBILITY
PRISMATIC
AN OBJECT HAVING A CONSTANT CROSS SECTIONAL AREA OVER ITS FULL LENGTH
PRISMATIC BAR
A BAR HAVING A CONSTANT CROSS SECTIONAL AREA OVER ITS FULL LENGTH
PRISMATIC COLUMN
A COLUMN HAVING A CONSTANT CROSS SECTIONAL AREA OVER ITS FULL LENGTH
PRODUCT OF INERTIA
A MATHEMATICAL MEASURE OF THE ROTATIONAL INERTIA OF AN OBJECT THAT
INVOLVES A PRODUCT OF X, Y, Z COORDINATES OF MASS PARTICLES THAT
MAKE UP AN OBJECT.
PROJECTION
FINDING OR MEASURING THE COMPONENT OF A DIRECTED (VECTOR) QUANTITY
(I.E. FORCE, VELOCITY, ACCELERATION,...) IN A SPECIFIC DIRECTION.
PROPORTIONAL LIMIT
OBJECTS THAT STRETCH WILL OFTEN STRETCH PROPORTIONATELY: WHEN THE
STRESS IS DOUBLES, THE STRAIN WILL DOUBLE. THIS BEHAVIOR WILL
BE TRUE ONLY UP TO SOME MAXIMUM LIMITING STRESS BEYOND WHICH THE
STRAIN WILL NOT INCREASE PROPORTIONATELY TO THE STRESS.
PROPORTIONAL LIMIT EXCEEDED
EXCEEDING THE LOAD STRESS FOR WHICH THE MATERIAL UNDER TEST BEHAVES
PROPORTIONATELY: STRESS PROPORTIONAL TO STRAIN
PROPPED CANTILEVER BEAM
A BEAM PINNED AT ONE END, EXTENDED AWAY FROM THE PIN AND SUPPORTED
BY A STRUCTURAL MEMBER (PROP).
PULLEY
A WHEEL WITH A GROOVE, ON AN AXLE THAT CARRIES A BELT, ROPE OR WIRE
THAT CAN BE USED TO PULL, LIFT OR OTHERWISE MOVE OBJECTS
PURE BENDING
PURE SHEAR
THE FLATTENING THAT SOMETIMES OCCURS WHEN AN OBJECT IS ELONGATED IN ONE DIRECTION
AND REDUCED IN SIZE AT RIGHT ANGLES TO THIS DIRECTION.
IN THE CASE OF A TWO DIMENSIONAL COORDINATE SYSTEM, THE TWO DIMENSIONAL
PLANE CAN BE DIVIDED BY 2 PERPENDICULAR STRAIGHT LINES. THESE
DIVIDE THE PLANE SPACE INTO FOUR SECTORS OR QUADRANTS.
STRESS WHICH OCCURS ALONG THE RADIAL DIRECTION, POINTING INWARDLY OR
OUTWARDLY.
RADIUS OF CURVATURE
THE RADIUS OF A PORTION OF A CURVED TRAJECTORY, PATH OR SHAPE.
RADIUS OF GYRATION
A CHARACTERISTIC DISTANCE USEFUL FOR PREDICTING ROTATIONAL MOVEMENT
WHICH IS CALCULATED FROM THE MOMENT OF INERTIA AND THE MASS OF AN
OBJECT.
RADIUS OF GYRATION
RATE OF TWIST
ANGULAR MEASURE OF THE TWIST PER UNIT LENGTH OR TIME
REACTION
A FORCE WHICH IS A RESPONSE OF A STRUCTURE OR ASSEMBLY TO AN APPLIED LOAD
REACTION FORCES
REACTIVE TORQUES
TORQUES (OR MOMENTS) THAT DEVELOP IN RESPONSE TO AN APPLIED LOAD MOMENT OR TORQUE.
RECTANGULAR
HAVING A CLOSED SHAPE WITH 4 SIDES, AT RIGHT ANGLES (PERPENDICULAR) TO EACH OTHER.
RECTANGULAR COMPONENTS
RECTILINEAR MOTION
MOVEMENT IN A STRAIGHT LINE
RECTILINEAR/CURVILINEAR TRANSLATION
TRANSLATION IS A FORM OF NONROTATIONAL MOTION IN WHICH ALL PARTS OF A
RIGID BODY EXPERIENCE THE SAME DISPLACEMENTS, VELOCITY, ACCELERATION
AT THE SAME TIME. RECTILINEAR TRANSLATION IS TRANSLATIONAL MOTION
ALONG A STRAIGHT LINE. CURVILINEAR TRANSLATION IS TRANSLATION MOVEMENT
FOLLOWING A CURVE PATH.
REDUNDANT CONSTRAINTS
REGULAR-SHAPED BODIES
OBJECTS WHOSE SHAPE IS A COMPOSITE OF ONE OR SEVERAL SIMPLE GEOMETRIC
SHAPES.
REINFORCED CONCRETE
REINFORCED CONCRETE BEAMS
BEAMS MADE OF CONCRETE THAT HAVE EMBEDDED FIBERS OR RODS TO STIFFEN
AND STRENGTHEN THE CONCRETE.
RELATIVE DISPLACEMENT
THE CHANGE IN POSITION OF AN OBJECT AS SEEN AND MEASURED BY AN OBSERVER ON
A MOVING COORDINATE SYSTEM.
RELATIVE MOTION
THE MOTION OF AN OBJECT AS SEEN AND MEASURED BY AN OBSERVER ON
A MOVING COORDINATE SYSTEM.
RELATIVE POSITION VECTOR
THE POSITION OF AN OBJECT AS SEEN AND MEASURED BY AN OBSERVER ON
A MOVING COORDINATE SYSTEM.
RELAXATION
THE LESSENING IN STRESS OF A STRAINED MATERIAL DUE TO CREEP AND RESULTING
IN PERMANENT DEFORMATION OF THE MATERIAL.
RESIDUAL STRAIN
A STRAIN WITHIN A SOLID THAT IS NOT DEPENDENT ON EXTERNAL FORCES.
RESIDUAL STRESS
A STRESS WITHIN A SOLID THAT IS NOT DEPENDENT ON EXTERNAL FORCES.
RESISTANCE STRAIN GAUGE
AN INSTRUMENT FOR DETERMINING STRAIN FROM A CHANGE IN ELECTRICAL RESISTANCE.
RESOLUTION
THE SMALLEST INCREMENT IN DISTANCE OR SIZE THAT CAN BE IDENTIFIED OR
CONTROLLED.
RESOLUTION OF A VECTOR
RESOLUTION OF A VECTOR INTO COMPONENTS
RESOLVE
TO SOLVE OR TO BE ABLE TO DISTINGUISH ON OBJECT FROM ANOTHER
RESONANCE
A STATE OF VIBRATION OR OSCILLATION WHERE AN EXTERNAL FORCE ACTS AT THE
SAME FREQUENCY AS THE NATURAL FREQUENCY. THE AMPLITUDE (SIZE) OF THE
VIBRATIONS WILL BECOME VERY LARGE WHEN THESE FREQUENCIES ARE THE SAME.
RESTORING MOMENT
A MOMENT OR TWISTING FORCE THAT TENDS TO RESTORE (RETURN) AN OBJECT
TO ITS EQUILIBRIUM POSITION.
RESULTANT
THE SUM OR NET RESULT FORCE (OR MOMENT) ACTING ON AN OBJECT. THIS IS
A SUM OF THE FORCES (OR MOMENTS) ACTING ON AN OBJECT.
RESULTANT
RESULTANT MOMENT
RESULTANT STRESS DISTRIBUTION
THE MANNER IN WHICH THE STRESS IS SPREAD OVER A STRUCTURE OR SUPPORTING
MEMBER.
RETROGRADE PRECESSION
A STATE OF SPIN AND PRECESSION OF A SPINNING TOP.
RIGHT HAND RULE
A RULE THAT USES DIRECTIONS GIVEN BY FINGERS ON THE RIGHT HAND TO DETERMINE
THE DIRECTION OF FIELDS AND FORCES.
RIGHT HAND RULE
RIGHT TRIANGLE
A TRIANGLE THAT HAS ONE 90O ANGLE.
RIGID BODY
AN OBJECT IN WHICH ALL THE COMPONENT PARTS REMAIN FIXED IN POSITION
RELATIVE TO EACH OTHER.
RIGID BODY
ROLLER SUPPORT
A SUPPORT FOR A BEAM, STRUCTURE OR ASSEMBLY THAT IS FREE TO ROLL.
ROTATION
MOTION OF ALL PARTS OF A BODY IN CIRCLES AROUND AN AXIS.
ROTATION ABOUT A FIXED AXIS
MOTION OF ALL PARTS OF A BODY IN CIRCLES AROUND AN AXIS THAT IS FIXED
IN POSITION AND ORIENTATION.
ROTATION OF AXES
A CHANGE IN ORIENTATION OF A SYSTEM OF COORDINATE AXES.
ROTATIONAL KINETIC ENERGY
ENERGY OF MOTION THAT COMES FROM ROTATIONAL MOVEMENT.
STRAINS THAT RESULT FROM APPLICATION OF FORCES AND MOMENTS THAT ARE STATICALLY
0 BECOME NEGLIGIBLE AT DISTANCES THAT ARE LARGE COMPARED WITH THE
DIMENSIONS OF THE PART.
SANDWICH BEAMS
A BEAM MADE OF STRUCTURAL TIMBERS BOLTED TOGETHER WITH A STEEL
PLATE BETWEEN THEM.
SCALAR
A NUMBER OR MEASUREMENT WITH ONLY A MAGNITUDE BUT NO DIRECTION
SCALAR DOT PRODUCT
A MATHEMATICAL EXPRESSION WHICH INVOLVED MULTIPLYING TWO VECTORS TO
GET A SCALAR RESULT.
SCALAR EQUATION
AN EQUATION WRITTEN IN TERMS OF SCALAR QUANITIES (MAGNITUDE ONLY,
NO DIRECTION REQUIRED)
SCALAR PRODUCT
A MATHEMATICAL EXPRESSION WHICH INVOLVED MULTIPLYING TWO VECTORS TO
GET A SCALAR RESULT.