fluids and heat
DESCRIPTION
Gives a brief description of several concepts on the topics of Fluid motion and Temperature and Heat.TRANSCRIPT
Most Awesome Teachers EVAR!!!!
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
)( 21 TTKA
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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
4ATet
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