Liquids Liquids Pressure = Force/Area Pressure = Force/Area Pressure Liquid = Weight Density x Depth...

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Liquids Liquids

Transcript of Liquids Liquids Pressure = Force/Area Pressure = Force/Area Pressure Liquid = Weight Density x Depth...

LiquidsLiquids

LiquidsLiquids

• Pressure = Force/AreaPressure = Force/Area

• Pressure Pressure LiquidLiquid = Weight Density x Depth = Weight Density x Depth

• 1 Liter 1 Liter waterwater = 1 kg = 1 kg

• Weight Density Weight Density waterwater = 1 = 1

• Pressure Pressure waterwater is a function of depth is a function of depth

• Greater depth = greater pressureGreater depth = greater pressure

• Lower depth = lower pressureLower depth = lower pressure

PressurePressure

• For liquids of equal densities, For liquids of equal densities, pressure at a certain depth will be pressure at a certain depth will be equal regardless of the mass or equal regardless of the mass or volume of liquidvolume of liquid

• This pressure is exerted in all This pressure is exerted in all directionsdirections

PressurePressure

• Total Pressure = Pressure Total Pressure = Pressure LiquidLiquid + + Pressure Pressure AtmosphereAtmosphere

• Pressure Pressure AtmosphereAtmosphere = 1 = 1• Water Water for every 10 m of depth you for every 10 m of depth you

gain 1 atmosphere of pressuregain 1 atmosphere of pressure• So…for 30 m of depth in water you So…for 30 m of depth in water you

experience how much total pressure?experience how much total pressure?• 4 ATM4 ATM

Density & DisplacementDensity & Displacement

• Completely submerged objects will Completely submerged objects will displace a volume displace a volume liquidliquid = volume = volume objectobject

• Displacement method used to Displacement method used to determine the volume of irregularly determine the volume of irregularly shaped objects (i.e.; engine blocks)shaped objects (i.e.; engine blocks)

• Density = mass/volumeDensity = mass/volume

Archimedes’s PrincipleArchimedes’s Principle

• An immersed object is buoyed up by An immersed object is buoyed up by a force equal to the weight of the a force equal to the weight of the fluid it displacesfluid it displaces

either completely or partially either completely or partially submerged submerged

objectsobjects true for liquids and gasestrue for liquids and gases

BuoyancyBuoyancy

• Loss of weight experienced by Loss of weight experienced by submerged objectssubmerged objects

• Buoyant Force Buoyant Force upward force a upward force a liquid exerts in opposition to gravityliquid exerts in opposition to gravity

• FFbuoybuoy = = VgVg

ρρ density of fluid density of fluid

V V Volume Volume

Density and Submerged Density and Submerged ObjectsObjects• Whether something sinks or floats in a Whether something sinks or floats in a

liquid is dependant upon how great the liquid is dependant upon how great the buoyant force is compared to the objects buoyant force is compared to the objects weightweight

• If the buoyant force equals the weight of If the buoyant force equals the weight of a submerged object, then the weight of a submerged object, then the weight of the object and the water displaced is the object and the water displaced is equal, therefore densityequal, therefore densityobjectobject = density = densitywaterwater

Density and Submerged Density and Submerged ObjectsObjects If an object is denser than the fluid in If an object is denser than the fluid in

which it is immersed, it will sinkwhich it is immersed, it will sink If an object is less dense than the If an object is less dense than the

fluid in which it is immersed, it will floatfluid in which it is immersed, it will float If an object has a density equal to If an object has a density equal to

the density of the fluid in which it is the density of the fluid in which it is immersed, it will neither sink or floatimmersed, it will neither sink or float

FloatationFloatation

• In order to float an object must In order to float an object must displace a weight of water equal to displace a weight of water equal to or greater than the weight of the or greater than the weight of the objectobject

• A floating object displaces a weight A floating object displaces a weight of fluid equal to it’s own weightof fluid equal to it’s own weight

Bernoulli’s EquationBernoulli’s Equation

• PP11 + ½ + ½ ρρvv1122 + + ρρgygy11 = P = P22 + + ρρvv22

22 + + ρρgygy22

• Statement of energy conservationStatement of energy conservation

• Explains how an airplane wing gets Explains how an airplane wing gets lift or why a curve ball curveslift or why a curve ball curves

ViscosityViscosity

• Internal resistance to flow in a liquidInternal resistance to flow in a liquid amount of internal friction within amount of internal friction within

a liquida liquid Water has a low viscosity with Water has a low viscosity with

very little internal resistance to flowvery little internal resistance to flow Syrup has a high viscosity with Syrup has a high viscosity with

lots of internal resistance to flowlots of internal resistance to flow

Pascal’s PrinciplePascal’s Principle

• Changes in pressure at any point in Changes in pressure at any point in an enclosed fluid at rest are an enclosed fluid at rest are transmitted undiminished to all transmitted undiminished to all points in the fluid, and acts in all points in the fluid, and acts in all directionsdirections

true for both liquids and gasestrue for both liquids and gases basis for hydraulics and basis for hydraulics and

pneumatics pneumatics