Fluids Flashcards by Sayan Basu

Liquid

ability to flow and conform to the shapes of their containers

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Gases and liquids are….

Fluids

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Only solids can withstand ____ forces, but both fluids and solids can exert _____ forces.

shear/tangential

perpendicular

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Density

scalar

p = m/v

g/mL or kg/m^3 or g/cm^3

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1 g/cm^3 = _____ kg/m^3

1000

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Weight of any Volume

Fg = density * volume * gravity

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Specific Gravity

density of a fluid compared to pure water @ 1 atm and 4 C

SG = density / 1(g/cm^3)

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Pressure

ratio of magnitude of force per unit area in pascals

P = F/A

scalar

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1 atm = ____ torr = _____ mmHg = 1.013*10^5 Pa

760

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1 Pa = _____ N/m^2

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Atmospheric Pressure

changes with altitude

impacts a number of processes including hemoglobins affinity for oxygen and boiling of liquids

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Absolute (Hydrostatic) Pressure

total pressure exerted on an object submerged within a fluid

P = Po + pgz

Po = ambient pressure (pressure at surface)

p = density

z = depth of object

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In open air and most situations Po = _____ but in other fluid systems the surface pressure may be higher or lower than atmospheric pressure.

1 atm

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Pressure cooker increases ____ to raise the ___ of water in food to reduce cooking time and prevent loss of moisture.

pressure

boiling point

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Gauge Pressure

difference between absolute pressure inside tire and armspheric pressure outside the tire

Pgauge = P - Patm = (Po + pgz) - Patm

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Hydrostatics

study of forces and pressures acting on fluids at rest

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Pascals Principle

an incompressible fluid with a change in pressure will have it transmitted through every portion of the fluid and the walls of the containing vessel

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Hydraulic Systems

take advantage of the near-incompressibility of liquids to generate mechanical advantage (pascals theory)

pressure is same across both piston areas, so forces are proportional based in ratio of areas

P = F1/A1 = F2/A2

F2 = F1 (A2/A1)

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Piston Displacement of Hydraulic systems

energy is conserved as volume displaced by piston 1 is equal to volume displaced in piston 2

V = A1d1 = A2d2

d2 = d1(A1/A2)

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Work Generated by Piston Hydraulic Systems

W = P*delta V = F/A (Ad)

W = F1d1 = F2d2

greater force through smaller distance

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Archimedes Principle

buoyancy of objects when placed in a fluid

any object placed in a fluid will cause a colume of fluid to be displaced equal to the volume of the object submerged

a body wholly/partially immersed in a fluid will be buoyed upwards by a force equal to the weight of the fluid it dispalces

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Buoyant Force

mass of fluid dispersed exerts a force equal to its weight against the submerged object

F = pfluid * Vfluid displaced * g = pfluid * Vsubmerged*g

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When an object is placed in a fluid, it will sink into the fluid only to the point at which the _________ exerts a force equal to the ________

volume of displaced fluid

weight of object

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If two objects placed in a fluid displace the same volume of liquid, they will experience ________ even if the objects themselves have different masses.

same magnitude of buoyant force

Specific Gravity and how much a floating object lies below the surface

if an objects specific gravity is expressed as a percent, it indicates the percent of the objecy submerged: ie. ice density if 0.92 g/cm^3 so its specific gravity is 0.92 and 92% of it is submerged

A specific gravity of exactly 1 indicates that _____

100% of the object will be submerged but it will not sink

Surface Tension

results from cohesion molecules have strong attractive forces on the molecules below them pulling surface of the liquid toward the center to produce the tension with a net upward force.

Cohesion

attractive force between molecules of liquid towards other molecules of same liquid

Adhesion

attractive force of liquid molecules to molecules of other substance

Meniscus

downward curved surface which forms when adhesive forces greater than cohesive

Convex Meniscus

Middle higher than the edges cohesive forces greater than the adhesive forces

Fluid Dynamics

study of fluids in motion

Assumptions For Fluid Dynamics

1) rigid walled containers | 2) uniform density of fluids

Viscosity

resistance of a fluid to dlow Pascal-second = N*s / m^2

Viscous Drag

caused by increased viscosity which is a non conservative force like air resistance

Inviscid

fluids which have no viscosity

More viscous fluids will _____ more energy while flowing.

lose

Laminar Flow

smooth and orderly, layers of fluid flow parallel to each other; HOWEVEr layers will not always have same linear speed ie: layers close to wall of pipe flow slower than those in the center

Posielles Law

with Laminar Flow in a confined space, rate of flow can be calculated Q = (pi*r^4 *delta pressure gradient)/ (8 * viscosity * Length) ***relationship of radius and pressure gradient is incerse exponential to the fourth power ; even a slight change in radius can effect the pressure gradient

Turbulence Flow

rough and disorderly forms eddies

Eddies

caused by turbulence flow; swirls of fluid of varying sizes occuring downstream of an obstacle

Critical speed

when turbulence occurs in unobstructed fluid flow depends on physical properties of the fluid like viscosity/diameter Vc = (reynolds number * viscosity )/ (density *diamerter)

Boundary Layer

when critical speed is exceeded, laminar flow occurs only in fluid adjacent to the wall

Reynolds number

depends on size, shape and surface roughness of an objects within the fluid

Streamlines

pathways followed by fluid eleents/particles as they move velocity vector is tangent to the stram line and they don't cross each other

Flow rate is ____ for a closed system and is ____ of changes in cross sectional area

constant independent

Linear Speed

measure of linear displacement of fluid particles in a given amount of time

While the flow rate is constant, the linear speed of the fluid _______ to the cross sectional area

does not change relative

Continuity Equation :Q = v1A1 = v2A2

Q flow rate v1 = linear speeds A = cross sectional area tells us fluids flow more quickly through narrow passages and slowly through wider onces

Bernoullis Equation

P1 + 1/2pv1^2 + pgh1 = P2 + 1/2pv2^2 + pgh2 P is absolute pressure of fluid p is density of fluid v is linear speed h is heigh of fluid sum of the staatic pressure and dynamic pressure will be constant within a closed contained for an incompressible fluid not experiencing viscous drag

Dynamic Pressure

pressure associated with movement of fluid 1/2pv^2

Static pressure

P + pgh

Venturi Flow Meter

pgh constant at both points h difference is difference in heights of the columns linear speed must increases as cross sectional area decreases dynamic pressure increases, absolute pressure decreases making fluid at venturi tube lower

Circulatory system is a _____ with a _____ flow rate. The ___ flow rate can be measured as a _____

closed loop non constant non constant pulse

As blood flows away from the heart, each vessel has _____ resistance until the capillaries, but resistance total decreases as the vessels are ___ with each other.

increased parallel

Return flow of blood to heart from skeletal muscles squeezing, _____ pressure in limbs to push blood to heart which has decreased pressure

increasing

Results of turbulent blood flow

heart murmurs

During inspiration, there is a ____ pressure gradient that moves air into lungs. During expatriation this gradient reverses. When air reaches the alveoli it has ______

negative essentially no