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OverviewFluid: A substance that flows

Usually a liquid or a gasHydrostatics: the study of a fluid at rest

Ex) Pressure at depthHydrodynamics: the study of a fluid in motion

Ex) Flow rateIdeal Liquid:

Incompressible (so that density does not change)Maintain a steady flow rateNon-viscousIrrotational flow

Hydrostatic PressureMeasure of the pressure a fluid exerts on the

walls of the containerSI Units: Newton per meter squared :

Aka the PascalSometimes measured in atmospheres (atm)

1 atm is the pressure exerted at sea level1 atm = 1.013 x 105 Pa

2m

N

Hydrostatic Pressure (cont)

p1 is at the surface and is 1 atmTo find pressure at depth (p2):p2 is the absolute pressure

the total static pressure at a certain depth in a fluid, including the pressure at the surface of the fluid

Difference in pressure: Gauge pressure: the difference between the static pressure at a certain depth in

a fluid and the pressure at the surface of the fluid Pressure at any depth does not depend of the shape of the

container, only the pressure at some reference level (like the surface) and the vertical distance below that level

h h hp2 p2 p2

p1 p1p1

ghpp 12

ghpp 12

BuoyancyBuoyancy is the weight of the displaced fluidArchimedes’ Principle states that a body

wholly or partly immersed in a fluid is buoyed up by a force equal to the weight of the fluid it displaces

Buoyant Force: the force that pushes the object upwards

Fluid Flow ContinuityFlow Rate Continuity: the volume or mass

entering any point must also exit that point

A = Area of the respective tubeV = Fluid speed in the respective pipeMass must be conserved, so mass in M1 = M2

A1

A2

v1 v2

Mass flow Rate: pAvDensity of fluid x Area of tube x velocity of fluid

in tubeEquation of Continuity: the flow rate through

tube 1 is the same as tube 2 so:1 A1 v1 = 2 A2 v2

Volume flow rate: the density of the fluid is the same throughout the pipeA1 v1 = A2 v2

A1

A2

v1 v2

Bernoulli’s PrincipleBernoulli’s Principle: the total pressure of a

fluid along any tube of flow remains constant

y = heightv = velocity of fluidIf density of the fluid is p then:

y1

y2

v1

v2

22

2212

11 2

1

2

1gyvpgyvp

Fluid moving through a horizontal pipe (y1 = y2):

This equation implies that the higher the pressure at a point in a fluid, the slower the speed, and vice-versa

Continuity Principle and Bernoulli’s Principle used together to solve for pressure and fluid speed

222

211 2

1

2

1vpvp

Part the second of Chris, Baby, and Kevin’s epic PowerPoint series

Mechanical Equivalent of HeatStates that heat and motion are virtually

interchangeable and in any circumstance a given amount of work would produce a given amount of heat

1 calorie of heat = 4.1868 joules per calorie

Heat TransferHeat Transfer: the movement of heat between

two substances, occurs through conduction, convection, and radiation

Conduction: heat transfer as the result of collisions between molecules in a material, or between material Since molecules in a solid are not free to move, this is accomplished

through vibrational kinetic energy

Convection: heat transfer as the result of mass movement of warm material from one region to another

Radiation: energy transfer as the result of electromagnetic waves

ConductionRate of heat flow through an object, as a

result of conduction

= heat transfer per unit timeA = cross sectional area of an object = object’s thicknessT = temperatureK = the thermal conductivity of the object

SI unit is kcal/(smC) : C = degrees Celsius

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RadiationStefan-Boltzmann’s Equation: calculates rate at

which an object radiates electromagnetic energy

= rate at which energy leaves the objectA = object’s surface areaT = object’s temperature in Kelvine = emissivity of the material

Perfect absorber is also a perfect emitter and e = 1

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