Chapter 6 Basic Physics for the Respiratory Therapist  Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Learning Objectives  Describe the properties that characterize the three states of matter.  Describe how heat transfer occurs among substances.  Identify the three common temperature scales and explain how to use them.  Describe how substances undergo change of state.

Learning Objectives (cont.)  Identify the factors that influence the vaporization of water.  Describe how water vapor capacity, absolute humidity, and relative humidity are related.  Describe how to predict gas behavior under changing conditions, including at extremes of temperature and pressure.  Describe the principles that govern the flow of fluids.

Lecture Outline Energy and matter States of matter Physical properties of liquids and gases Gas laws Fluid mechanics Principles of electricity Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 4

Physics  Branch of science that deals with interaction of matter and energy  Fields that make up physics:  Mechanics  Optics  Acoustics  Electricity  Magnetism  Thermodynamics Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Energy and Work 1 meter  Work is product of force and distance  Energy and work are expressed in joules (J)  One joule is force required to move 1 kilogram 1 meter  Power measures rate at work being performed  Watts (W) is unit of measure for power Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Energy and Matter  Energy is the ability to do work  Types of energy  Mechanical  Thermal  Chemical  Sound  Nuclear  Electrical Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Energy and Matter (Cont.)  Law of conservation of energy  Energy cannot be created or destroyed, only transferred  Work = transfer of energy by mechanical means  Mechanical energy  Kinetic energy  Potential energy Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Types of Energy  Kinetic energy – associated with movement  Potential energy – amount of energy an object has due to its position  When coal is burned, its potential energy is released Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Energy and Matter (Cont.)  Kinetic energy = ½ (mv2)  Potential energy = mgh (mass, force of gravity, (mass,velocity)  Examples  Breaking of chemical bonds  Hitting a ball  Burning of fuel  Water over a falls height of the object)  Examples  Coiled spring  Stretched rubber band  Bicycle at top of hill  Ice before it melts Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 10

States of Matter  Matter – anything that has mass and occupies space  Matter – Composed of atoms (elements)  Atoms combine to form molecules – compounds/mixtures Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

States of Matter (Cont.) Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

States of Matter  Solids, Liquids, Gases  Solids  Have high degree of internal order  Fixed volume and shape  Strong mutual attractive force between atoms  Molecules have the shortest distance to travel before collision  This motion referred to as a “jiggle”

States of Matter (cont.)  Liquids  Have fixed volume, but adapt to shape of their container  Atoms exhibit less degree of mutual attraction compared w/ solids  Shape is determined by numerous internal & external forces  Gases  No fixed volume or shape; weak attractive forces  Gas molecules exhibit rapid, random motion w/ frequent collisions

States of Matter (Cont.) Gas condensation vaporization deposition sublimation Liquid Energy of system melting freezing Solid Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

States of Matter (Cont.)  Evaporation – liquid to gaseous state  Condensation – gas to liquid  Both essential components in respiration Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

States of Matter (Cont.)  Critical temperature  Critical pressure  Gases versus vapors Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

States of Matter (Cont.)  Vapor exists below critical temperature  May go back and forth when pressure is applied  Above critical temperature true gas exists  Most common vapors – H2O, CO2, and N2O Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

States of Matter (Cont.)  True gas exists above its critical temperature  Cannot be converted to a liquid no matter how much pressure is applied  Examples: Air, O2, and He  Water between 100°C on 374°C can be converted back from steam to liquid by applying high pressure.  >374°C water can exist only as a gas was no matter how much pressure is applied Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Physical Properties of Matter  Temperature  Pressure  Density  Buoyancy  Viscosity  Surface Tension Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 20

Temperature  The measure of average kinetic energy of molecules in an object  Thermometers are used to measure temperature  Types of thermometers  Nonelectrical  Electrical Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Types of Thermometers  Mercury thermometer – best example of nonelectrical thermometer  Electrical thermometer – works on principle that resistance of metal increases with temperature  Example of electrical: thermistor – resistance changes with changes in temperature. It is used with physiologic monitoring Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Temperature Scales  Temperature Scales  Fahrenheit (F) & Celsius (C) scales based on property of water  0° C is freezing point of water  - 273° C = kinetic molecular activity stops = 0° K  Kelvin scale (° K ) based on molecular motion  Used by SI (Systeme Internationale) units  Zero point = to absolute zero

Temperature Conversions Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Formulas °C = 5/9 (°F – 32) °F = (9/5 x °C) + 32 K = °C + 273 Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Practice Temperature Conversions 1. 25°C = ?°F 2. 35°C = ?°F 3. 37°C = ?°F 4. 39°C = ?°F 5. 39°C = ? k 6. 70°F = ?°C 7. 78°F = ?°C 8. 90°F = ?°C 9. 103°F = ?°C 10. 103°F = ? k Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Pressure Conversion: Units  cm H2O  mm Hg  psi (lb/in2)  atm  kPa Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Pressure Conversions = kPa  cm H2O x 0.7355 = mm Hg  cm H2O x 0.098  mm Hg  760 = atm  atm x 14.7 = psi Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Practice Pressure Conversions 25 cm H2O = ? mm Hg 30 cm H2O = ? mm Hg 90 mm Hg = ? cm H2O 760 mm Hg = ? cm H2O 760 mm Hg = ? kPa 2 atm = ? mm Hg 2000 psi = ? atm Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Density  Defined as mass per unit of volume  D = mass/volume  Solids are the most dense  Gases are the least dense  A block of wood is much more dense than a block of Styrofoam, if both are the same size; Styrofoam is much more likely to float Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 30

Buoyancy  When an object is submerged in water it will be buoyed up by a force equal to the weight of water displaced by the weight of fluid that is displaced by the object (Archimedes Principle) Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Viscosity cohesive forces between its molecules. easily  Defined as force opposing fluid flow  The viscosity of a fluid is directly proportional to the cohesive forces between its molecules.  Oil at low temperature has high viscosity  As it is heated its viscosity decreases and it flows more easily Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Physical Properties of Liquids and Gases  Cohesion & adhesion  Attractive force between like molecules = cohesion  Attractive force between unlike molecules = adhesion  Surface tension: Force exerted by like molecules at liquid’s surface (why bubbles retain spherical shape) Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Physical Properties of Liquids and Gases (Cont.)  Surface tension: adhesive forces  Attractive forces between two different kinds of molecules  Example: water and glass Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Physical Properties of Liquids and Gases (Cont.)  Surface tension: cohesive forces  Attractive forces between like kinds of molecules Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Physical Properties of Liquids and Gases (Cont.)  LaPlace’s Law  Pressure within a sphere is directly related to the surface tension of the liquid and inversely related to the radius of the sphere  P = 2 (ST/r) Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Change of State (cont.)

Change of State (cont.)

The Gas Laws Pressure  Boyle’s Law  Avogadro’s Law  Charles’s Law  Graham’s Law  Gay-Lussac’s Law  Fick’s Law of Diffusion  Combined Gas Law  Dalton’s Law of Partial Pressure Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 39

Properties of Gases frequent collisions  Kinetic activity of gases  Gas molecules travel at high speeds in random fashion w/ frequent collisions  Velocity of gas molecules is directly proportional to its temperature

Properties of Gases (cont.)  Gaseous diffusionmovement of molecules from areas of high concentration to areas of lower concentration  Gas pressure  All gases exert pressure  Gas pressure in a liquid is known as gas “tension”  Atmospheric pressure is measured with a barometer  Partial pressure = pressure exerted by single gas in gas mixture

Boyle’s Law  Temperature is constant  Gas volume is inversely proportional to the absolute pressure exerted on it  PV = k  V1P1 = V2P2 Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Charles’s Law  Pressure is constant  Volume of gas varies directly with the temperature of the gas  V / T = k  V1 / T 1 = V2 / T2 Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Gay-Lussac’s Law  Volume is constant  Pressure varies directly with the absolute temperature of the gas  P / T = k  P1 / T1 = P2 / T2 Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Boyle’s Law PV = k Charles’s Law V / T = k Ideal Gas Law PV = nRT P and V change n, R, T are constant T and V change P, n, R are constant Ideal Gas Law PV = nRT P, V, and T change n and R are constant Combined Gas Law PV / T = k Copyright © 2014 by Mosby, an imprint of 45 Elsevier Inc.

Combined Gas Law Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Dalton’s Law of Partial Pressure Dalton’s law  partial pressure of gas in mixture is proportional to its percentage in mixture The sum of the partial pressures of the individual gases. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Solubility of gases in liquids (Henry’s law)  The solubility coefficient equals the volume of a gas that will dissolve in 1 ml of a given liquid at standard pressure and specified temperature.  Solubility of gases in liquids (Henry’s law)  Volume of gas dissolved in a liquid is a function of its solubility coefficient & its partial pressure  Gases can dissolve in liquids. Carbonated water and soda are good examples of a gas (CO2) dissolved in a liquid (water).  Temperature plays a major role in gas solubility. High temperatures decrease solubility, and low temperatures increase solubility. The effect of temperature on solubility is a result of changes in kinetic activity. As a liquid is warmed, the kinetic activity of any dissolved gas molecules is increased Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 48

Avogadro’s Law 6.02 x 1023 molecules  Equal volumes of gases, at the same temperature and pressure, contain equal numbers of molecules  1 gram molecular weight (gmw) = 1 mole  1 mole of any gas occupies 22.4 L at 0° C and contains 6.02 x 1023 molecules Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Avogadro’s Law Example  1 mole of oxygen (mw = 32 g) occupies a volume of 22.4 L and contains 6.02 x 1023 molecules when measured at 0° C  Density (g/L) = gmw of gas / 22.4 L Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Graham’s Law  Diffusion is rate at which two gases mix  Rates of diffusion of 2 gases are inversely proportional to the square root of their masses Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Graham’s Law (Cont.) r1 / r2 = √d2 / d1  Mass of a gas is directly proportional to its density at a constant temperature r1 / r2 = √d2 / d1 Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Fick’s Law of Diffusion Many Molecules Few Molecules Resistance depends on the dimensions and properties of the membrane Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Fluid Mechanics  Flow patterns  Poiseuille’s law  Reynolds’ number  Bernoulli principle  Venturi principle  Coanda phenomena Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Flow Patterns •Study of fluids in motion = hydrodynamics •Pressure exerted by liquid in motion depends on nature of flow itself •Progressive decrease in fluid pressure occurs as fluid flows through tube due to resistance 56

Flow Patterns streamlines  Patterns of flow  Laminar flowfluid moving in discrete cylindrical layers or streamlines  Poiseuille’s lawpredicts pressure required to produce given flow using ΔP = 8nl V./ πr4  Turbulent flowloss of regular streamlines; fluid molecules form irregular eddy currents in chaotic pattern is predicted by using Reynold`s number (NR)  NR = v d2r / h

Flow Patterns Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Poiseuille’s Law n viscosity, L length of tube, r radius of tube.  Flow through a tube  Q = (P1 – P2) / R(Resistance)  Resistance to flow through a tube  R = (8ήL) / (π r4) n viscosity, L length of tube, r radius of tube.  Note that decreasing the radius by one half increases the resistance 16 fold (Asthma) Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Reynolds’ Number  Dimensionless number related to pattern of flow to indicate whether fluid flow past a body or in a duct is steady or turbulent.  NR = v × d × (2r/ή)  V = velocity of flow  r = radius of the tube  d = density of the gas  ή = viscosity  NR >2000 means turbulent flow predominates Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 60

Fluid Mechanics: Bernoulli The Bernoulli effect  Fluid passing through tube that meets constriction experiences significant pressure drop  Fluid that flows through constriction increases its velocity while lateral wall pressure decreases Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 61

Fluid Mechanics: Venturi The pressure drop that occurs distal to the constriction in a tube can be restored to the pre-constriction pressure if there is a dilation in the tube distal to the constriction with an angle of divergence not exceeding 15 degrees. Copyright © 2014 by Mosby, an imprint of 62 Elsevier Inc.

Fluid Mechanics Fluid entrainment  Velocity of fluid (gas) can increase greatly at point of constriction  Causing lateral pressure to fall below atmospheric pressure  If open tube is placed distal to constriction, another fluid can be pulled into primary flow stream (fluid entrainment) Copyright © 2014 by Mosby, an imprint 63 of Elsevier Inc.

Fluid Mechanics: Venturi (Cont.) This design helps keep the percentage of entrained fluid constant, even when the total flow varies. Copyright © 2014 by Mosby, an imprint of 64 Elsevier Inc.

Fluid Mechanics Fluidics & Coanda effect  Fluidics is branch of engineering applying hydrodynamics principles in flow circuits  Coanda effect (wall attachment) is observed when fluid flows through small orifice w/ properly contoured downstream surfaces Copyright © 2014 by Mosby, an imprint 65 of Elsevier Inc.

Fluid Mechanics: Coanda Effect (Cont.)  Add contoured tube distal to the constriction and the gas will adhere to the wall of the contoured tube because:  Negative pressure past constriction draws fluid toward the curved extension  Ambient pressure pushes the fluid stream against the wall Copyright © 2014 by Mosby, an imprint of 66 Elsevier Inc.