Physics 111Lecture 1Units

Dr. Ali ÖVGÜNEMU PhysicsDepartment

www.aovgun.com

CourseInformation:Instructor• Instructor:AliÖvgün• Office:AS245(ArtsandSciencesFaculty)• Officehour:Tobeannounced(checkmywebpage).Othertimebyappointment

• Email:ali.ovgun@emu.edu.tr• Website:www.aovgun.com• Physics Lab Exemptions http://physics.emu.edu.tr/

CourseInformation:Materials• LectureClasses:

– PHYS111(03)12:30-14:20,WED PHAR- A220– PHYS111(01)12:30-14:20WEDPHAR219TUTORIALORLAB– PHYS111(01)14:30-16:20THURPHAR226– PHYS111(03)14:30-16:20THURPHAR219TUTORIALORLAB– Lecturenotesavailableatwww.aovgun.com

– PrimaryTextbook:1)J.W.Jewett,Jr.andR.A.Serway,PhysicsforScientistsandEngineerswithModernPhysics.2)Halliday,Resnick,Walker,PrinciplesofPhysics.

• LabMaterial:“Physics Laboratory Manual ”

CourseInformation:• MidtermExam(35%)

• LabExperiments(5%)

• LabExam(10%)

• FinalExam(50%)

• FinalLetterGrade• Participationtolaboratory:• Attendingatleast3outof4experimentsisamust,

otherwisethestudentwilldirectlygetNGfromthelecture.

COURSESCHEDULE• 1st WeekChapter1– Units• 2nd WeekChapter3– Vectors• 3rd WeekChapter2– MotioninOneDirection• 4th WeekChapter5– TheLawsofMotion• 5th WeekChapter6– CircularMotionandOtherApplicationsofNewton’s

Laws• MidtermExam• 6th WeekChapter7– EnergyofaSystem• 7th WeekChapter8– ConservationofEnergy• 8th WeekChapter14– FluidMechanics• 9th WeekChapter23– ElectricFields• 10th WeekChapter29– MagneticFields• 11th WeekX-Rays• 12th WeekNuclearStructure(Radioactivity)• FinalExam

Physics

• Physicsdealswiththenatureandpropertiesofmatterandenergy. Commonlanguageismathematics.Physicsisbasedonexperimentalobservationsandquantitativemeasurements.

• Classicalmechanicsdealswiththemotionandequilibriumofmaterialbodiesandtheactionofforces.

TheQuick6:SixUnitConversionDisasters

• Thinkyouhadabaddayatwork?

• Forgettingtoconvertunitscanresultinbig-timedisasterslikethesesixexamples.

1.Canyouimaginelosing$125millionthankstoalittlemetricsystemerror? That’sexactlywhathappened in1999whenNASAlostaMarsorbiterbecauseoneteamusedmetricunitsforacalculationandtheotherteamdidn’t.

2.In1983,anAirCanadaplaneranoutoffuelinthemiddleofaflight. Thecause?Notonebut twomistakesinfiguring howmuchfuelwasneeded.ItwasAirCanada’sfirstplanetousemetricmeasurementsandclearlynoteveryonehadthehangofityet.Luckily,noonewaskilledandonlytwopeople receivedminor injuries.That’samazingconsidering theflightcrewthought theyhaddouble thefueltheyactuallyhad.

Pharmacist• In1999,theInstituteforSafeMedicationPracticesreportedaninstancewhereapatienthadreceived0.5gramsofPhenobarbital(asedative)insteadof0.5 grainswhentherecommendationwasmisread.Agrainisaunitofmeasureequaltoabout0.065grams…yikes.TheInstituteemphasizedthatonlythemetricsystemshouldbeusedforprescribingdrugs.

Chapter1Measurement• BeingquantitativeinPhysicsrequiresmeasurements• HowtallisMingYao?Howabouthisweight?

– Height:2.29m(7ft6in)– Weight:141kg(310lb)

• Number +Unit

– “thicknessis10.”hasnophysicalmeaning– Bothnumbersandunits necessaryforanymeaningfulphysicalquantities

TypeQuantities• Manythingscanbemeasured:distance,speed,energy,time,force……

• Thesearerelatedtooneanother:speed=distance/time

• Choosethreebasicquantities:– LENGTH:Meter– MASS:Kilogram– TIME:Second

• Defineotherunitsintermsofthese.• In1960,standardsbodiescontrolanddefineSystème Internationale (SI)unitas,

FundamentalQuantitiesandSIUnitsLength meter m

Mass kilogram kg

Time second s

Electric Current ampere A

Thermodynamic Temperature kelvin K

Luminous Intensity candela cd

Amount of Substance mole mol

Whyshould wecareaboutSIunits?MarsClimateOrbiter: http://mars.jpl.nasa.gov/msp98/orbiter

SILengthUnit:Meter• FrenchRevolutionDefinition,1792• 1Meter=XY/10,000,000• 1Meter=about3.28ft• 1km=1000m,1cm=1/100m,1mm=1/1000m

• CurrentDefinitionof1Meter:thedistancetraveledbylightinvacuumduringatimeof1/299,792,458second.

SITimeUnit:Second

• 1Secondisdefinedintermsofan“atomicclock”– timetakenfor9,192,631,770oscillationsofthelightemittedbya133Csatom.

• Definingunitspreciselyisascience(important,forexample,forGPS):– Thisclockwillneithergainnorloseasecondin20millionyears.

SIMassUnit:Kilogram• 1Kilogram– themassofaspecific

platinum-iridiumalloykeptatInternationalBureauofWeightsandMeasuresnearParis.(Seekingmoreaccuratemeasure:http://www.economist.com/news/leaders/21569417-kilogram-it-

seems-no-longer-kilogram-paris-worth-mass)• Copiesarekeptinmanyothercountries.• YaoMingis141kg,equivalenttoweightof

141piecesofthealloycylinder.

January 21, 2015

Length, Mass, Time

PrefixesforPowersofTen

DerivedQuantitiesandUnits• Multiplyanddivideunitsjustlikenumbers• Derivedquantities:area,speed,volume,density……

– Area=Length* Length SIunitforarea=m2

– Volume=Length* Length* LengthSIunitforvolume=m3

– Speed=Length/time SIunitforspeed=m/s– Density=Mass/Volume SIunitfordensity=kg/m3

• In2008OlympicGame,UsainBoltsetsworldrecordat9.69sinMen’s100mFinal.Whatishisaveragespeed?

m/s 10.32sm

9.69100

s 9.69m 100speed =⋅==

UsainBolt setanewworldrecordof9.58seconds inthemen's100matthe2009WorldChampionships inBerlin,aspeedof23.3mph(10.416m/s).MarkWebber hadthehighestaveragespeedof119.61mphinhisRedBullatF1'sHungarianGrandPrixinJuly.Mallard,aClassA4steamlocomotive,setthesteamlocomotionlandspeedrecord- 125.88mph- on3July1938.FredMarriott hasheldthecurrentlandspeedrecordforsteam-poweredvehiclessince1906,whenhereached127.659mphinhisStanleycar.The BritishSteamCarteam saytheircarhasreached137.14mphintesting,butthisisanunofficialfigure.Theyhopetoreachupto170mphintheirrecordattempt(indicatedbyyellowbar).British-built ThrustSSC settheworldlandspeedrecordinOctober1997,reaching763.035mphinadesertintheUSstateofNevada.The speedofsound changesaccordingtofactorsincludingtemperatureandaltitude,butastandardfiguregivenisroughly768mph.

1mph=0.44704m/s

6AnimalsFasterThanUsainBoltIt’swellknownthatJamaicansprinterand100mworldrecordholder, UsainBolt,isthefastesthumanonEarth.Buthowdoeshecomparetohisspeedyanimalcounterparts?Bolt’sworldrecordof9.58secondsforthe100mraceinBerlin2009placeshimatatopspeedof30mphwithanaveragespeedof23.5mph.However, thesesixanimalslistedfromslowesttofastest,leavehiminthedust,reachingdoubleandeventriplethetopspeedsthatBoltwouldonlydreamofeverachieving.Whenitcomestospeedefficiency,Boltcouldlearnathingortwofromhisfurry friends.

1. NorthAfricanOstrich40mph

2.Greyhound43mph

3.ThoroughbredRacehorse55mph

4.Pronghorn Antelope55mph

5.Cheetah61mph

OnJune20,2012sheran100min5.95secondswithatopspeedof61mph.That’snearly4secondsfasterthanBolt’s100mworldrecordandmorethandoublehistopspeed.

6.PeregrineFalcon161mph

Fasterthanasportscar,thissmallpredatorcanreachuptoatopspeedof161mph.That’sfivetimesfasterthanBolt’stopspeed.

2.3miles->cm?1mile=5,280ft,1ft=12in,1in=2.54cm

1,000,000,000micrograms

UnitConversion• Example:Ishespeeding?

– OnthegardenstateparkwayofNewJersey,acaristravelingataspeedof38.0m/s.Isthedriverexceedingthespeedlimit of75mi/h?

– Sincethespeedlimitisinmiles/hour (mph), weneedtoconverttheunitsofm/stomph.Takeitintwosteps.

– Step1:Convertmtomiles.Since1mile=1609m,wehavetwopossibleconversionfactors,1mile/1609m=6.215x10−4 mile/m,or1609m/1mile=1609m/mile.Whataretheunitsoftheseconversionfactors?

– Sincewewanttoconvertmtomile,wewantthemunitstocancel=>multiplybyfirstfactor:

– Step2:Convertstohours.Since1hr=3600s,againwecouldhave1hr/3600s=2.778x10−4 hr/s,or3600s/hr.

– Sincewewanttoconvertstohr,wewantthesunitstocancel=>

2m 1mile 38.0 mile38.0 2.36 10 mile/ss 1609m 1609 s

−⎛ ⎞⎛ ⎞ ⋅ = ⋅ = ×⎜ ⎟⎜ ⎟⎝ ⎠ ⎝ ⎠

2 mile 3600 s38.0 m/s 2.36 10 85.0 mile/hr = 85.0 mphs hr

−= × ⋅ =

1mile=1609m

Summary• Thethreefundamentalphysicalquantitiesofmechanicsare

length,massandtime,whichintheSIsystemhavetheunitsmeter(m),kilogram(kg),andsecond(s),respectively

• Themethodofdimensionalanalysisisverypowerfulinsolvingphysicsproblems.

• Unitsinphysicsequationsmustalwaysbeconsistent.Convertingunitsisamatterofmultiplyingthegivenquantitybyafraction,withoneunitinthenumeratoranditsequivalentintheotherunitsinthedenominator,arrangesotheunwantedunitsinthegivenquantityarecancelledoutinfavorofthedesiredunits.

Estimation:CountingBrainCells• Estimatethemassofyourbrainandthenumberofcellsitcontains

January 21, 2015

Answers:4000rad,25×10&'𝑀𝑒𝑣/𝑔

Ans:355.2×1001𝑚3

Ans:7692tablets

Ans:0.15L

Ans:3months

Ans:992.25kg/𝑚3

Ans:558.7µmol/L

Ans:88.03g,20 kg