Physics Principles Flashcards
Atom
Unit of Matter
Protons, neutrons, electrons
Atomic Number
protons in nucleus of atom
Atomic Mass
proteins, neurons in nucleus
Isotope
Atom of element with unusual # of neutrons in nucleus
Strong, Interatomic Bonds
- Covalent Bonds: atoms share outer shell of electrons
- Ionic Bonds: transfer of electron btw atoms
Weak, Intermolecular Bonds
- Hydrogen bonds
- Van der Waals forces
–Dipole-dipole - btw polar substances
–London Dispersion forces - weakest, btw non polar substances
Fluid
Substance that deforms continuously under application of a shear (ie tangential) stress
Freezing Pt
Liquid –> solid
Boiling Pt
Liquid –> gas
Condensation Pt
Gas –> liquid
Melting Pt
Solid –> liquid
Latent Heat
Energy req’d to transform matter from one state to another
Critical Temperature
–gases can be liquified by increasing pressure or by cooling
–Temp at which no amt of pressure will liquify gas
Critical Pressure
Pressure above which liquid and gas cannot coexist at any temp
VP at critical temperature
Critical Volume
Volume occupied by one mole of gas at critical temp, pressure
Triple Point
T, P where all three states of substance coexist in thermodynamic equilibrium
Critical Point
Liquid, vapor
Gas, vapor forms of substance coexist with same density and are indistinguishable
R of triple pt
Newton’s First Law
Object remains at constant velocity unless acted on by an outside force
Newton’s Second Law
Force = Mass x Acceleration
Force: SI unit = Newton (kg*m/s^2)
Used for von Frey filaments, other aesthesiometers
von Frey Filaments
mechanical sensitivity test
thin plastic filaments applied to plantar surface of hind paw - filaments of different gauges/stiffness used to determine threshold that elects hind paw withdrawl
Velocity
Rate of change of position
Magnitude + direction
Vector
Acceleration
Rate of change of velocity
Newton’s third law
For every action, there is an equal and opposite reaction
Forces must add up
Weight
Measure of gravitational force exerted on mass
Weight = mass x acceleration DT gravity
Technically measured in Newton’s
M
Mass
Amt of matter an object contains
g
Energy
Capacity to Do Work
Work
Result of a force acting on an object in order to move said object
SI unit = joules (kg*m^2/s^2)
Work = force x distance (defibrillator)
Work = pressure x volume (PV loops)
Power
rate of doing work
SI unit = watt –> power expended when one Joule of work consumed in 1 second (J/s0
Efficiency
Efficiency = Energy output/energy input *100%
Pressure
Force per unit area
P=F/A
Pascal, Pa (N/m^2)
Newtonian Fluid
Viscosity unaffected by flow velocity, shear rate
Non Newtonian Fluid
Viscosity will change depending on shear rate
Viscosity
Fluid’s resistance to flow
Results from frictional forces btw layers
Content of fluid affects viscosity as well eg polycythemia
Temp inversely related
Viscosity coefficient (eta)
Constant for Newtonian fluids
eta = shear stress, shear rate
Fahraeus-Lindqvist effect
Decrease in blood viscosity in very small vessels (10-200um) DT erythrocytes lining up in middle of vessel with plasma on periphery
LaPlace’s law
Cylinder: T=PR
–vessels, conducting airways
Spherical Vessel: T=PR/2
–Alveoli, surfactant
Examples: RBB, LV hypertrophy, DCM
RBB and LaPlace’s Law
RBB can prevent barotrauma as one source of compliance in the breathing system
LVH and LaPlace’s Law
Persistent increase in LV overload (aortic stenosis) leads to increase LV pressure, so higher wall stress
Also applies to RVH
DCM and LaPlace’s Law
LV radius increases, greater wall tension need to develop same LV pressure
Air Embolism and LaPlace’s law
Pressure DT surface tension on meniscus which has smaller radius of curvature = higher than that acting on meniscus on other side of bubble
Laminar Flow
Parabolic Flow Pattern
Fastest at center, slowest at periphery
HP law
Turbulent Flow
Fluid flows unpredictably
Turbulence predicted by Reynold’s #
DENSITY
> 4000 flow turbulent, <2000 laminar, 2000-4000 = transitional with regions of both
Bernoulli Principle
Increase in flow velocity of ideal fluid accompanied by simultaneous reduction in pressure
pressure energy, kinetic energy, and potential energy equal on both sides
Increase in speed of fluid occurs simultaneously with reduction in static pressure or decrease in potential energy
Venturi Mask
Illustration of Bernoulli principle
Valve = high air flow oxygen entrainment valve
Uses injector - reduction of pressure DT high flow of oxygen, entrains air into O2 flow
Jet Entrainment
If hole in low pressure area (eg construction), fluid can be entrained from outside
Gas
Gaseous substance that normally in gaseous state at room temp, ATM pressure
Henry’s Law
Vapor
gaseous substance normally liquid at room temp, ATM pressure
vapor formed via evaporation
Jet Entrainment
If hole in low pressure area (eg construction), fluid can be entrained from outside
Gas
Gaseous substance that normally in gaseous state at room temp, ATM pressure
Vapor
gaseous substance normally liquid at room temp, ATM pressure
vapor formed via evaporation
Henry’s Law
Cx = k(h)*Px
Amt of gas dissolved in liquid directly proportional to pp of gas in equilibrium with liquid
Vapor
gaseous substance normally liquid at room temp, ATM pressure
vapor formed via evaporation
Coanda Effect
-Fluid will hug convex contour when flowing tangential to surface
-Effect = maldistribution of fluid flow
-Uneven distribution of flow in alveoli or myocardial infarction
Entrainment Ratio
DT both Bernoulli effect and jet entrainment
ER = entrained flow/driving flow
Three ways circle system cannot be arranged?
Unidirectional valves must go btw RB, P
FGF cannot enter btw exp valve, P
APL valve cannot be btw p, insp v
Adiabatic Compression or Expansion of Gases
Occurs without adding or removing energy from system
Why crack tanks before use
Jet Entrainment
If hole in low pressure area (eg construction), fluid can be entrained from outside
Gas
Gaseous substance that normally in gaseous state at room temp, ATM pressure
Fluid Logic and the Coanda Effect
Switching flow ventilator valve uses effect to advantage, supply oxyge/ventilation to patient but also allows expiratory venting without moving parts
Hygroscopic Material
attracts moisture from atmosphere
Thermometer: liquid in gas
uses liquid expansion with temp change
mercury thermometers
Bourdon Thermometer
Pressure change of gas
Thermistor
Uses T sensitivity resistor (semiconductor): as T falls, R increases
Thermocouple
Uses Seebeck effect, two different conductive materials
Seebeck effect: conductor generates voltage when exposed to T as a gradient
Infrared tympanic thermometers
thermopile to measure radiation emitted by eardrum
prone to false low readings
Wavelength
Distance btw identical points on consecutive waves
Amplitude
Distance btw origin and crest/trough
Frequency
of waves that pass point per unit time
Speed
wavelength x frequency
Isobestic point
Point at which two substances absorb certain wavelength of light to same extent
Simple Harmonic Motion
Motion repeats self, takes same time each cycle
Relationship btw mass, time vary in sinusoidal fashion
Harmonic Series
Occur when other frequencies which have frequencies that are exact multiples of the original are overloaded with initial (=fundamental) frequency
ex Fournier analysis
Fournier Analysis
Analysis, generation of various biological signals by breaking down any periodic waves into component sine, cosine waveforms
eg ABP, EEG, ECG
Doppler Effect
Frequency (and therefore pitch) of sound rises as it approaches observer and falls as it moves away
DT relationship of waves and observer, still occurs with no actual velocity change
US, laser
Piezo-Electric Effect
–Production of electrical current DT deformation of certain materials
Piezo-Electric Effect
–Production of electrical current DT deformation of certain materials
–Crystals frequently used for this purpose eg accelerometers, Doppler probes, US
–Electric current passing through crystals generates US waves, receiving crystals deformed by reflected sound waves –> produce electrical signal –> processed into image, sound
Ohm’s law
V=IR
Voltage = Current * Resistance
Related to:
Change in pressure = Flow * Resistance
(vascular resistance)
Electrical Circuits
Resistors in series: Total = R1+R2+R3
Parallel: total = 1/R1+1/R2
Ex BV
Pseudocritical Temperature
Applies to a mixture of gases
temperature at which gas mixtures separate into their component parts
Critical Velocity
speed at which a falling object reaches when both gravity, air resistance are equalized on the object.
speed, direction at which the fluid can flow through a conduit without becoming turbulent.
Joules
Derived unit of SI energy
Conveys energy transferred to an object when 1 Newton force acts on object in direction of forces motion through a distance of 1m
