1-properties of liquids[1]
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11 PropertiesofLiquidsPropertiesofLiquids
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11DifferencebetweenFluids&Solids
Fluids may be liquids (definite volume;freesurface) or gases (expand to fill anycontainer).
Fluid
is
a
body
of
matter
that
canflow;
i.e.
continuestodeformunderashearingforce.
Solid hasacertainvolumeandshape
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Fluids
Liquid Gas
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12Propertiesofaliquid
121 Density
Massperunitvolume
Units
gmmass/cm
3
Kgmass/m3
3L
M
Volume
Mass
=
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122SpecificWeight
Specificweightisdefinedastheweightofthe
substanceperunitvolume
Unitsgm/cm3 ,N/m3 ,Kg/cm3 ,ton/m3
gL
gM
L
F
Volume
Weight=
=
33
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1221Units
Nkgmkgkg
mKgNcmgmgm
ggmgmgmassWeight
onacceleratimassF
mass
mass
mass
mass
81.91sec/81.911
sec/111sec/9811
11
2
2
2
=
=
=
=
=
=
=
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123Specificweight&specificGravity
RelativeDensityS SpecificGravityG
Cowater
liquidG4@
=
Cowater
liquid
S4@
=
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124Viscosity
Viscosityisthepropertyofliquidthatindicates
theresistanceofliquidagainstmotion.Viscositycanbedescribedeitherby
dynamicviscosity
kineticviscosity
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DynamicViscosity
dyduVelocity
Shear
/ydepthatgradient
ydepthaatstress
==
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Where
is the shear stress at depth y is the dynamic viscosity of the liquiddu/dy is the velocity gradient at depth y
dydu/
=
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1241Dynamicviscosityunits
2
211
sec/sec// cmgmcmgm
FTLTML
mass
1 poise = 0.1 N sec/m2
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1242KineticViscosity
sec/212 cmTL
=
1 stoke = 1 cm2/sec
The kinetic viscosity is affected by temperature
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125Vaporpressure
Thevaporpressureisdefinedas thepressureof
theatmosphereadjoiningtheliquidatwhichtheliquidstartstoevaporate
Allliquidspossesatendencytovaporizewhenexposedtogaseousatmosphere.
Thevaporpressuredependson:
i.Theliquidtemperature.
ii.Atmosphericpressureadjoiningtheliquid.
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126Compressibility
A fluid is comprisable when its density
changeswithchangeofpressureactingonit.
Inreality allfluidsarecompressible.
The compressibility of liquid is measured by
BULKMODULUSOFELASTISITYK
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1261BulkModulusofElasticityK
VV
PK
=
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Continue BulkModulusofElasticityK
The water compressibility increase with the
increase of temperature up to 50oC, then it
startstodecrease.
Themodulusofelasticityforfreshwaterat20oC
istoosmallthatitconsideredasincompressible
fluid
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127SurfaceTension
Molecules of liquid held together by force
attraction.Theyareequallyattracted. The resultant of these forces at the solid
boundary containing the liquid surface
tension
Surface Tension is a force in the liquid
surface and acts normal to the line of unit
lengthdrawnimaginaryonthesurface.