I.IntroductionDefinition: Physics deals with the combination of matter and energy. It also deals with a wide variety of systems, about which theories have been developed that are used by physicists. In general, theories are experimentally tested numerous times before they are accepted as correct as a description of Nature (within a certain domain of validity). For instance, the theory of classical mechanics accurately describes the motion of objects, provided they are much larger thanatomsandmovingatmuchlessthanthespeedoflight.BranchesofPhysicsClassical mechanics is a model of the physics of forces acting upon bodies. It is often referred toas"Newtonianmechanics"afterIsaacNewtonandhislawsofmotion.

Classicalmechanics

Secondlawofmotion

Thermodynamics studies the effects of changes in temperature, pressure, and volume on physical systems on the macroscopic scale, and the transfer of energy as heat. The starting point for most thermodynamic considerations is the laws of thermodynamics, which postulate thatenergycanbeexchangedbetweenphysicalsystemsasheatorwork.

Electromagnetism, or the electromagnetic force is one of the four fundamental interactions in nature, the other three being the strong interaction, the weak interaction, and gravitation. This force is described by electromagnetic fields, and has innumerable physical instances including

the interaction of electrically charged particles and the interaction of uncharged magnetic force fieldswithelectricalconductors.

Electricity*Magnetism MichaelFaraday AndrMarieAmpreOptics is the branch of physics which involves the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describesthebehaviourofvisible,ultraviolet,andinfraredlight.The theory of special relativity was proposed in 1905 by Albert Einstein in his article "On the Electrodynamics of Moving Bodies". The theory is based on two postulates: (1) that the mathematical forms of the laws of physics are invariant in all inertial systems and (2) that the speed of light in a vacuum is constant and independent of the source or observer. Reconciling the two postulates requires a unification of space and time into the framedependent concept of spacetime. General relativity is the geometrical theory of gravitation published by Albert Einstein in 1915/16. It unifies special relativity, Newton's law of universal gravitation, and the insight that gravitation can be described by the curvature of space and time. In general relativity, the curvatureofspacetimeisproducedbytheenergyofmatterandradiation.

AlbertEinstein

Quantum mechanics is the branch of physics treating atomic and subatomic systems and their interaction with radiation. It is based on the observation that all forms of energy are released in discreteunitsorbundlescalled"quanta".Totheinterdisciplinaryfields,whichdefinepartiallysciencesoftheirown,belonge.g.the:

astrophysics, the physics in the universe, including the properties and interactions of

celestialbodiesinastronomy.

biophysics,studyingthephysicalinteractionsofbiologicalprocesses.

chemicalphysics,thescienceofphysicalrelationsinchemistry.

econophysics, dealing with physical processes and their relations in the science of

economy.

geophysics,thesciencesofphysicalrelationsonourplanet.

medicalphysics,theapplicationofphysicstoprevention,diagnosis,andtreatment.

physical chemistry, dealing with physical processes and their relations in the science

ofphysicalchemistry.

TheRealmsofPhysics

TheRealmsofPhysics

Slow Fast(>1%speedoflight)

Large Classical Relativity

Small(Submicroscopic) QuantumMechanics RelativisticQuatumMechanics

I.Introduction

a.PhysicsintheHealthSciences 1

Athletics. Kinesiology (literally the study of motion), is based on the relationship between distance, time, velocity, and acceleration, as well as the concepts of force, work, energy, and power. Studying these related concepts will allow you a deeper understanding of the body, its muscles, its utilization of energy in terms of underlying physics that may already be intuitively familiar. For example, it will be clear why it is harder to carry an object at arms length than close to the body. Experiencemakesitobvious,butphysicstellswhy.Traction Systems. Some traction systems seem to have wires, pulleys, and weights going every which way and performing altogether mysterious tasks. The studyofforceshelpsexplaintractionsystems.Nutrition and Exercise. Work is the manifestation of energy in changing forms. In humans, work changes stored energy into heat, motion, and other forms of energy.Body Temperature. Humans and other warmblooded animals maintain a constant body temperature by converting food energy to heat energy. However, the body continues to produce heat even when surrounding temperatures are higher than body temperature. Excess heat is dissipated by perspiring and it is the bodys only method of dissipating heat when surrounding temperatures are high. It will also be seen why an alcohol rub reduces body temperature, as might be necessary with a high fever. The concept of efficiency makes it evident that the body creates even more heat than normal during exercise since a large fraction of the food energy used in producing muscle contractions ends up as heat instead (efficiency is less than 100%). As a consequence, the body requires morecoolingandperspiresmoreduringexercisethanwhenatrest.Physical Therapy. Patients undergoing physical therapy usually have weakened or damaged muscles or suffer from nerve disorders that make it difficult for them to move their muscles effectively. A great deal of physical therapy takes place in water because the water helps to support the weight of the person. Being in water greatly reduces the effective weight of the person and of his limbs, making it possible for him to perform exercises that would be impossible out of the water. The underlying physical principle is called Archimedes principle. The physics of fluidshastremendousnumberofapplicationsinbiologicalsystems.

1PhysicswithHealthScienceApplications,PaulPeterUrone.

Blood Flow and Respiration. Liquid and gases can be made to move by the application of pressure. The flow of liquids and gases has important biological roles. For example, the heart creates blood pressure by exerting force on the blood with a muscular contraction. The subsequent blood flow is regulated by blood vessels changing diameter and thereby changing their resistance to flow. Other examples of the bodys use of pressure include breathing, maintenance of reduced pressure in the chest cavity to keep the lungs from collapsing, and pressureintheeyetomaintainitsshape.Hearing. Hearing is the perception of sound. Sound is a wave phenomenon and hearing does not simply reproduce the actual properties of sound. For example, loudness is the perceived intensity of sound waves. However, humans does not perceive ultrasound at all, so loudness is not a perfect indication of intensity and hencediffersfromthatphysicalcharacteristic.Ultrasonic Scanners. Ultrasound is any sound that is so highpitched the average person cannot hear it. Ultrasound still behaves in a fashion similar to audible sound waves. For example, it scatters from boundaries between substances and so can be used to probe the inside of the body noninvasively, much as submarines use sonar to view objects in dark waters. Ultrasonic waves can be made perfectly safe by keeping their intensity low enough. If this is done, theultrasoundcannotcauseinjurybecauseitlackstheenergytodoso.Electrical Safety. Certain medical procedures make hospital patients extremely sensitive to electrical shock. Major methods of protection must be studied. These include the threewire system, proper grounding of appliances, and the use of circuitbreakers.Nervous System. The nervous system is a complex of biological electric circuits that controls the muscles, among other things. Bioelectricity can be recorded and interpreted to yield a great deal of information on the functioning of certain body organs. The most common such recording is the electrocardiogram, literally a recording of the electrical impulses that control the beating of the heart. Electrocardiograms give detailed information about brain functions by recording itselectricalimpulsesinanelectroencephalogram.Vision. Most people consider their vision to be their most important sense. Among aspects of vision that have their explanation in the laws of physics are how the eye forms an image on the retina and the correction of common vision defects.Thelawsofopticscanalsodescribethenearmiracleofvision.From Microwave Deep Heating to Sunlamps. These are but two examples of applications of electromagnetic waves. Electromagnetic (EM) waves take many

forms, including radio waves, microwaves, visible light, ultraviolet light (as from a sunlamp), and gamma rays. The behavior of all these EM waves is analogous to that of sound waves. Learning the essential physics behind EM waves will make it possible to understand why they exhibit so many different properties. For example, microwaves can be used for deep heating, while ultraviolet waves cannot ultraviolet waves cause both tanning and sunburn and can be used to sterilizeobjectsevenifthewavesareverydim.Spectroanalysis. Spectroanalysis is a useful tool in the detection of trace amounts of toxic substances. Spectroanalysis is based on the fact that all elements and compounds emit EM spectra that are uniquely characteristic of the particular substance. The uniqueness of the atomic spectra is explained by atomic physics. Spectroanalysis is used in medicine and a host of other disciplines from chemistry to astronomy. It was used as a tool long before atomic physicswasunderstood.X Rays. X rays are part of the EM spectrum that are useful as a diagnostic tool in medicine. The study of the effects of radiation on biological organisms show that x rays are hazardous and cannot be made perfectly safethat is, their use involvesacalculatedrisk.Radiotherapy, Radiation Diagnostics, and Radiation Protection. It is possible to understand the uses as well as the hazards of radiation. The energy and other characteristics of radiation and the physical laws governing it give insight into these problems and help one gain the ability to assess for oneself the risk versus thebenefit.These are but a few of the numerous applications of physics in the health sciences.

b.Models,Theories,andLaws

A model is an analogy to objects or phenomena that are generally familiar and can be experienced directly. Models serve as very useful mental images to help picture what is going on in a system that cannot be sensed directly. One example is the planetary model of the atom, which pictures electrons orbiting the nucleus justasplanetsorbitthesun. 2Amodelbecomesafullfledgedtheoryifitiswidelysuccessfulinitsapplications. 3

2PhysicswithHealthScienceApplications,PaulPeterUrone.3PhysicswithHealthScienceApplications,PaulPeterUrone.

A scientific law describes what happens in nature in a general way. An example is Newtons laws of motion, which accurately describe the relationship between motionandforce. 4

c.Length,Mass,andTime:TheBasicUnits

Tocommunicatetheresultofameasurementofacertainphysicalquantity,aunitfor the quantity must be defined. If our fundamental unit of length is defined to be 1.0 meter, for example, and someone familiar with our system of measurement reports that a wall is 2.0 meters high, we know that the height of the wall is twice the fundamental unit of length. Likewise, if our fundamental unit of mass is defined as 1.0 kilogram and we are told that a person has a mass of 75 kilograms, then thatpersonhasamass75timesasgreatasthefundamentalunitofmass.In 1960 an international committee agreed on a standard system of units for the fundamental quantities of science, called SI (Systme International). Its units of length,mass,andtimearethemeter,kilogram,andsecond,respectively.LengthIn 1799 the legal standard of length in France became the meter, defined as one tenmillionth of the distance from the equator to the North Pole. Until 1960, the official length of the meter was the distance between two lines on a specific bar of platinumiridium alloy stored under controlled conditions. This standard was abandoned for several reasons, the principal one being that measurements of the separation between the lines are not precise enough. In 1960 the meter was defined as 1,650,763.73 wavelengths of orangered light emitted from a krypton86 lamp. In October 1983 this definition was abandoned also, and the meter was redefined as the distance traveled by light in vacuum during a time interval of 1/299,792,458 second. This latest definition establishes the speed of lightat299,792,458meterspersecond.MassThe SI unit of mass, the kilogram, is defined as the mass of a specific platinumiridium alloy cylinder kept at the International Bureau of Weights and MeasuresatSvres,France.

4PhysicswithHealthScienceApplications,PaulPeterUrone.

The National Standard Kilogram No. 20, an accurate copy of the International Standard Kilogram kept at Svres, France, is housed under a double bell jar in a vault at the National Institute of StandardsandTechnology.

TimeBefore 1960, the time standard was defined in terms of the average length of a solar day in the year 1900. (A solar day is the time between successive appearances of the Sun at the highest point it reaches in the sky each day.) The basic unit of time, the second, was defined to be (1/60)(1/60)(1/24) = 1/86,400 of the average solar day. In 1967 the second was redefined to take advantage of the high precision attainable with an atomic clock, which uses the characteristic frequencyofthelightemittedfromthecesium133atomasitsreferenceclock.Thesecondisnowdefinedas9,192,631,770timestheperiodofoscillationofradiationfromthecesiumatom.

Acesiumfountainatomicclock.Theclockwillneithergainnorloseasecondin20millionyears.

Physics is a science in which mathematical laws are tested by experiment. No physical quantity can be determined with complete accuracy because our senses are physically limited, even when extended with microscopes, cyclotrons, and other instruments. Consequently, its importanttodevelopmethodsofdeterminingtheaccuracyofmeasurements.All measurements have uncertainties associated with them, whether or not they are explicitly stated. The accuracy of a measurement depends on the sensitivity of the apparatus, the skill of the person carrying out the measurement, and the number of times the measurement is repeated. Once the measurements, along with their uncertainties, are known, its often the case that calculations must be carried out using those measurements. Suppose two such measurementsaremultiplied.When a calculator is used to obtain this product, there may be eight digits in the calculator window, but often only two or three of those numbers have any significance. The rest have no value because they imply greater accuracy than was actually achieved in the original measurements. In experimental work, determining how many numbers to retain requires the application of statistics and the mathematical propagation of uncertainties. In a textbook it isnt practical to apply those sophisticated tools in the numerous calculations, so instead a simple method, called significant figures, is used to indicate the approximate number of digits that should be retained at the end of a calculation. Although that method is not mathematically rigorous,itseasytoapplyandworksfairlywell.Suppose that in a laboratory experiment we measure the area of a rectangular plate with a meter stick. Lets assume that the accuracy to which we can measure a particular dimension of the plate is . If the length of the plate is measured to be 16.3 cm, we can claim only that it .1cm 0 lies somewhere between 16.2 cm and 16.4 cm. In this case, we say that the measured value has three significant figures. Likewise, if the plates width is measured to be 4.5 cm, the actual value lies between 4.4 cm and 4.6 cm. This measured value has only two significant figures. We could write the measured values as and . In general, a significant figure 6.3 .1cm1 0 .5 .1cm4 0 is a reliably known digit (other than a zero used to locate a decimal point). Note that in each case, the final number has some uncertainty associated with it, and is therefore not 100% reliable. Despite the uncertainty, that number is retained and considered significant because it doesconveysomeinformation.

Suppose we would like to find the area of the plate by multiplying the two measured values together. If the measured values are then the final value can nd(4.5 .1cm)(16.3 .1cm) 0 a 0 rangebetween

4.5 .1cm) 16.3 .1cm)(4.5 .1cm) 16.2cm)(4.4cm) 1.28cm(16.3 .1cm) 0 ( 0 = ( 0 0 = ( = 7 2 and

4.5 .1cm) 16.3 .1cm)(4.5 .1cm) 16.4cm)(4.6cm) 5.44cm(16.3 .1cm) 0 ( 0 = ( + 0 + 0 = ( = 7 2 Claiming to know anything about the hundredths place, or even the tenths place, doesnt make any sense, because its clear we cant even be certain of the units place, whether its the 1 in 71, the 5 in 75, or somewhere in between. The tenths and the hundredths places are clearly not significant. We have some information about the units place, so that number is significant. Multiplyingthenumbersatthemiddleoftheuncertaintyrangesgivesand

4.5cm) 3.35cm(16.3cm) ( = 7 2 which is also in the middle of the areas uncertainty range. Because the hundredths and tenths are not significant, we drop them and take the answer to be 73 cm2, with an uncertainty of . cm 2 Note that the answer has two significant figures, the same number of figures as the least accuratelyknownquantitybeingmultiplied,the4.5cmwidth.Calculations as carried out in the preceding paragraph can indicate the proper number of significant figures, but those calculations are timeconsuming. Instead, two rules of thumb can be applied. The first, concerning multiplication and division, is as follows: In multiplying (dividing) two or more quantities, the number of significant figures in the final product (quotient) is the same as the number of significant figures in the least accurate of the factors being combined, whereleastaccuratemeanshavingthelowestnumberofsignificantfigures.MeasurementMeasurementistheprocessofcomparingaquantityfromagivenstandard.Everyquantitythatyouseeinphysicalformulasisameasuredquantity.

Metric/SIPrefix

A metric prefix or SI prefix is a unit prefix that precedes (comes before) a basic unit of measure

to indicate a decadic multiple (multiples of ten) or fraction of the unit. The prefix kilo, for

example, may be added to gram to indicate multiplication by one thousand one kilogram is equal

to one thousand grams. The prefix centi, likewise, may be added to meter to indicate division by

onehundredonecentimeterisequaltoonehundredthofameter.

FundamentalUnits

A set of fundamental units is a set of units for physical quantities from which every other unit can

be generated or derived. In the language of measurement, quantities are quantifiable aspects of

the world, such as time, distance, velocity, mass, temperature, energy, and weight, and units are

used to describe their measure. In the SI system, there are seven fundamental units: kilogram,

meter,candela,second,ampere,kelvin,andmole.

SIFundamentalUnits

Measure

Symbol

Name

Current(2005)Definition

HistoricalOrigin

Dimension

Symbol

CorrespondingSymbolin

Equations

length m meter "Themetreisthelengthofthepathtravelledbylightin

vacuumduringatimeintervalof1299792458ofa

second."17thCGPM(1983,

Resolution1,CR,97)

110,000,000ofthedistancefromtheEarth'sequatortotheNorthPolemeasuredonthecircumferencethroughParis.

L l or d or s

mass kg kilogram "Thekilogramistheunitofmassitisequaltothemassoftheinternationalprototype

ofthekilogram."3rdCGPM(1901,CR,70)

Themassofonelitreofwater.Alitreisonethousandthofacubicmetre.

M m

time s second "Thesecondisthedurationof9192631770periodsoftheradiationcorrespondingtothetransitionbetweenthetwo

hyperfinelevelsofthegroundstateofthecaesium133

atom."13thCGPM(1967/68,Resolution1CR,103)

"Thisdefinitionreferstoacaesiumatomatrestata

temperatureof0K."(AddedbyCIPMin1997)

Thedayisdividedin24hours,eachhourdividedin60minutes,each

minutedividedin60seconds.

Asecondis1(246060)ofthe

day

T t

electriccurrent

A ampere "Theampereisthatconstant

currentwhich,ifmaintained

intwostraightparallel

conductorsofinfinitelength,

ofnegligiblecircular

crosssection,andplaced1

metreapartinvacuum,would

producebetweenthese

conductorsaforceequalto2

107newtonpermetreof

length."

9thCGPM(1948)

Theoriginal

"International

Ampere"was

defined

electrochemically

asthecurrent

requiredtodeposit

1.118milligramsof

silverpersecond

fromasolutionof

silvernitrate.

Comparedtothe

SIampere,the

differenceis

0.015%.

I I

temperature

K Kelvin "Thekelvin,unitof

thermodynamictemperature,

isthefraction1273.16of

thethermodynamic

temperatureofthetriplepoint

ofwater."

13thCGPM(1967/68,

Resolution4CR,104)

"Thisdefinitionreferstowater

havingtheisotopic

compositiondefinedexactly

bythefollowingamountof

substanceratios:0.000155

76moleof2Hpermoleof1H,

0.0003799moleof17Oper

TheCelsiusscale:

theKelvinscale

usesthedegree

Celsiusforitsunit

increment,butisa

thermodynamic

scale(0Kis

absolutezero).

T

moleof16O,and0.0020052

moleof18Opermoleof16O."

(AddedbyCIPMin2005)

amountof

substance

mol mole "1.Themoleistheamountofsubstanceofasystemwhichcontainsasmanyelementaryentitiesasthereareatomsin0.012kilogramofcarbon12

itssymbolis'mol.'2.Whenthemoleisused,

theelementaryentitiesmust

bespecifiedandmaybe

atoms,molecules,ions,

electrons,otherparticles,or

specifiedgroupsofsuch

particles."

14thCGPM(1971,

Resolution3CR,78)

"Inthisdefinition,itis

understoodthatunbound

atomsofcarbon12,atrest

andintheirgroundstate,are

referredto."

(AddedbyCIPMin1980)

Atomicweightormolecularweightdividedbythemolarmass

constant,1g/mol.

N n

luminousintensity

cd candela "Thecandelaistheluminous

intensity,inagivendirection,

ofasourcethatemits

monochromaticradiationof

frequency5401012hertzand

thathasaradiantintensityin

Thecandlepower,

whichisbasedon

thelightemitted

fromaburning

candleofstandard

properties.

J I

thatdirectionof1/683watt

persteradian."

16thCGPM(1979,Resolution3CR,100)

Note: The steradian (symbol: sr) or squared radian is the SI unit of solid angle. It is used in

threedimensional space, and functions analogously to the manner in which the radian quantifies

planar angles. The name is derived from the Greek stereos for "solid" and the Latin radius for

"ray,beam".

ThesevenSIbaseunitsandtheinterdependencyoftheirdefinitions:forexample,toextractthedefinitionofthe

metrefromthespeedoflight,thedefinitionofthesecondmustbeknownwhiletheampereandcandelaareboth

dependentonthedefinitionofenergywhichinturnisdefinedintermsoflength,massandtime.

RedefinitionoftheSIunits

"The ampere is that constant current which, if maintained in two straight parallel conductors of

infinite length, of negligible circular crosssection, and placed 1 metre apart in vacuum, would

producebetweentheseconductorsaforceequalto2107newtonpermetreoflength." 5

Under the proposals to redefine the ampere as a fixed number of elementary charges per

second, the electric constant would no longer have an exact fixed value. The value of the

electronchargewouldbecomeadefinednumber,notmeasured. 6

A committee of the International Committee for Weights and Measures (CIPM) has proposed

revised formal definitions of the SI base units, which are being examined by the CIPM and which

may be considered by the 25th 'General Conference on Weights and Measures', in 2014. The

metric system was originally conceived as a system of measurement that was derivable from

nature. When the metric system was first introduced in France in 1799 technical problems

necessitated the use of artifacts as the prototype meter and kilogram. In 1960 the meter was

redefined in terms of the wavelength of light from a specified source, making it derivable from

59thCGPM(1948).6OnthepossiblefuturerevisionoftheInternationalSystemofUnits,theSI.Svres,France:InternationalBureauforWeightsandMeasures.21Oct2011.Itisnotexpectedtobeadopteduntilsomeprerequisiteconditionsaremet,andinanycasenotbefore2014.

nature, but the kilogram has been defined by an artifact ever since its introduction. If the

proposed redefinition is accepted, the metric system (SI) will, for the first time, be wholly

derivablefromnature.

Theproposalcanbesummarisedasfollows:

"There will still be the same seven base units (second, meter, kilogram, ampere, kelvin,

mole, and candela). Of these, the kilogram, ampere, kelvin and mole will be redefined by

choosing exact numerical values for the Planck constant, the elementary electric charge,

the Boltzmann constant, and the Avogadro constant, respectively. The second, meter

and candela are already defined by physical constants and it is only necessary to edit

their present definitions. The new definitions will improve the SI without changing the size

ofanyunits,thusensuringcontinuitywithpresentmeasurements."

The seven base units in the SI system. Arrows point from units to those that depend on them as the accuracy oftheformerincrease,sowilltheaccuracyofthelatter.

ConversionofUnitsSometimes it is necessary to convert units from one system to another. Conversion factors between the metric/SI and British/English/US customary systems for units of length are as follows:

mi 609km1 = 1 ft 0.48cm1 = 3 m 9.37in .281ft1 = 3 = 3 in .54cm .0254m1 = 2 = 0

For example, we want to convert 15.0 inches to centimeters. We can multiply 15.0 in by (1.00 in/1.00),whichisequalto1.Butbecause1in=2.54cm,wefindthat

15.0incheswasmultipliedby1(because2.54cmdividedby1inequals1)andyieldsanumberequalto15.0inches,butthistimeincentimeters(38.1cm).

Exercise:

ConversionChartforLength

ConversionChartforArea

ConversionChartforVolume

ConversionChartforWeight

ConversionChartforLiquidVolumes

ConversionofTemperature

Cto F F C 2 : = 59 + 3

F to C C ( F 2) : = 95 3

CtoK K C 73 : = + 2 to C C K 73K : = 2