Liquids

Liquids Pressure = Force/Area Pressure = Force/Area Pressure Liquid = Weight Density x Depth Pressure Liquid = Weight Density x Depth 1 Liter water = 1 kg 1 Liter water = 1 kg Weight Density water = 1 Weight Density water = 1 Pressure water is a function of depth Pressure water is a function of depth Greater depth = greater pressure Greater depth = greater pressure Lower depth = lower pressure Lower depth = lower pressure

Pressure For liquids of equal densities, pressure at a certain depth will be equal regardless of the mass or volume of liquid For liquids of equal densities, pressure at a certain depth will be equal regardless of the mass or volume of liquid This pressure is exerted in all directions This pressure is exerted in all directions

Pressure Total Pressure = Pressure Liquid + Pressure Atmosphere Total Pressure = Pressure Liquid + Pressure Atmosphere Pressure Atmosphere = 1 Pressure Atmosphere = 1 Water  for every 10 m of depth you gain 1 atmosphere of pressure Water  for every 10 m of depth you gain 1 atmosphere of pressure So…for 30 m of depth in water you experience how much total pressure? So…for 30 m of depth in water you experience how much total pressure? 4 ATM 4 ATM

Density & Displacement Completely submerged objects will displace a volume liquid = volume object Completely submerged objects will displace a volume liquid = volume object Displacement method used to determine the volume of irregularly shaped objects (i.e.; engine blocks) Displacement method used to determine the volume of irregularly shaped objects (i.e.; engine blocks) Density = mass/volume Density = mass/volume

Archimedes’s Principle An immersed object is buoyed up by a force equal to the weight of the fluid it displaces An immersed object is buoyed up by a force equal to the weight of the fluid it displaces  either completely or partially submerged objects  either completely or partially submerged objects  true for liquids and gases  true for liquids and gases

Buoyancy Loss of weight experienced by submerged objects Loss of weight experienced by submerged objects Buoyant Force  upward force a liquid exerts in opposition to gravity Buoyant Force  upward force a liquid exerts in opposition to gravity F buoy =  Vg F buoy =  Vg ρ  density of fluid V  Volume

Density and Submerged Objects Whether something sinks or floats in a liquid is dependant upon how great the buoyant force is compared to the objects weight Whether something sinks or floats in a liquid is dependant upon how great the buoyant force is compared to the objects weight If the buoyant force equals the weight of a submerged object, then the weight of the object and the water displaced is equal, therefore density object = density water If the buoyant force equals the weight of a submerged object, then the weight of the object and the water displaced is equal, therefore density object = density water

Density and Submerged Objects  If an object is denser than the fluid in which it is immersed, it will sink  If an object is denser than the fluid in which it is immersed, it will sink  If an object is less dense than the fluid in which it is immersed, it will float  If an object is less dense than the fluid in which it is immersed, it will float  If an object has a density equal to the density of the fluid in which it is immersed, it will neither sink or float  If an object has a density equal to the density of the fluid in which it is immersed, it will neither sink or float

Floatation In order to float an object must displace a weight of water equal to or greater than the weight of the object In order to float an object must displace a weight of water equal to or greater than the weight of the object A floating object displaces a weight of fluid equal to it’s own weight A floating object displaces a weight of fluid equal to it’s own weight

Bernoulli’s Equation P 1 + ½ ρv ρgy 1 = P 2 + ρv ρgy 2 P 1 + ½ ρv ρgy 1 = P 2 + ρv ρgy 2 Statement of energy conservation Statement of energy conservation Explains how an airplane wing gets lift or why a curve ball curves Explains how an airplane wing gets lift or why a curve ball curves

Viscosity Internal resistance to flow in a liquid Internal resistance to flow in a liquid  amount of internal friction within a liquid  amount of internal friction within a liquid  Water has a low viscosity with very little internal resistance to flow  Water has a low viscosity with very little internal resistance to flow  Syrup has a high viscosity with lots of internal resistance to flow  Syrup has a high viscosity with lots of internal resistance to flow

Pascal’s Principle Changes in pressure at any point in an enclosed fluid at rest are transmitted undiminished to all points in the fluid, and acts in all directions Changes in pressure at any point in an enclosed fluid at rest are transmitted undiminished to all points in the fluid, and acts in all directions  true for both liquids and gases  true for both liquids and gases  basis for hydraulics and pneumatics  basis for hydraulics and pneumatics