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ScienceTutor:PhysicalScience
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Table of Contents
ii TableofContents
1 Introduction/HowtoUseThisBook
2 AUniverseofMotion,Forces,and
Energy
Part 1: Measuring Tools
3 MeettheMetricSystem
4 MeasuringWithMetrics
Part 2: The Mechanics of Motion
5 MeasuringSpeedandvelocity
7 GetReady,GetSet,Accelerate!
8 ConservingMotherMo(mentum)
9 AFeelingforForces
10 Newton’sBig3
11 FreeFa-a-allandGravity
12 ForcesinFluids
13 WorkandPower
14 Machines
15 PuttingItAllTogether
Part 3: All About Energy
16 Energy,letMeCountItsForms
17 KineticEnergy:TheEnergyofMotion
18 PotentialEnergy:TheEnergyofPosition
19 EnergyConversions
20 MovingHeatAround:Thermodynamics
21 ConserveEnergy—That’sthelaw!
22 ThelawsofThermodynamics
23 Entropy:AMeasureofDisorder
24 PuttingItAllTogether
Part 4: Electricity and Magnetism
25 Force,Charge,andAtomicStructure
26 ElectricForcesandFields
27 MagnetsandMagneticInduction
28 MagneticFields
29 Forces,ElectricCurrents,andMagnetic
Fields
30 linkingMovingChargesandChanging
MagneticFields
31 EMFsandCircuits
32 Ohm’slawandResistance
33 PowerProductionandTransformers
34 PuttingItAllTogether
Part 5: Waves of Light and Sound
35 WavesandTheirProperties
36 TypesandSpeedsofWaves
37 WaveInteractions
38 SoundandItsProperties
39 MixingSoundWaves
40 UsingSound
41 ElectromagneticWaves
42 TheElectromagnetic(em)Spectrum
43 visiblelight:A“Wavicle”
44 PuttingItAllTogether
45 AnswerKeys
TableofContents
ScienceTutor:PhysicalScience
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Introduction/How to Use This Book
Physical Scienceexplorestheuniverseofmotion,forces,andenergythatswirlsaboutusdailybutissometimestakenforgranted.Sincethemetricsystemiscrucialtoallscientificmeasurements,abrief introductionandreview isprovided inPart1:MeasuringTools,beforelaunchingintothemechanicsofmotionandforcesinPart2.Ametricruleisprintedonpage3,butyoumaywanttoprovideyourownrulersandmetricmeasuresforsomeactivities.Part3 examines energy in all its forms, and discusses energy conversions, thermodynamics,energyconservation,andentropy.Buckle-upinParts4and5inordertotacklethesubjectsofelectricandmagneticforcesandfieldsandridethewavesoflight,sound,andothervibratingdisturbances. Allofthesetopicsparallelnationalscienceteachingstandardsforthephysicalsciencesinmiddleschoolandabove.Thisworktextwillserveasagoodreviewofconceptsforsomestudents,anextraopportunityforotherstoworkwithdifficultconceptsagain,andcanevenserveasateacher’sguideforanexpandedprogramofinstruction. Keytermsappearboldfacedinthetext.Absorbsectionsintroducenewconcepts.Applysectionsallow the reader toexercisehisorherknowledgeof thecontentandconceptsbyansweringquestions,fillingintheblanks,andengaginginshortactivities.Afewexercisesmayrequireadditionalpaper;acalculatormayalsobeuseful.Attheendofeachsection,thereaderisinvitedto“putitalltogether”andtesthisorherunderstandingofthatsection. Workbooks are never a substitute for hands-on opportunities with simple machines,batteries,circuits,prisms,andmagnets.Trytohaveavailableasmanyofthesematerialsastimeandbudgetwillallow.IfyouareamemberoftheNationalScienceTeachersAssociation,there is some quite useful software available at www.scilinks.org for creating and tinkeringwithelectriccircuitsina“virtuallaboratory,”whereyoucanexplodelightbulbsandfrycircuitswithouthavingtoraidtheemergencyequipmentfund. Enjoytheexcitinguniverseofmotion,forces,andenergy!
Introduction/HowtoUseThisBook
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AUniverseofMotion,Forces,andEnergy
A Universe of Motion, Forces, and Energy
Aspaceshuttlecanliftapayloadequalingtheweightof6.6tyrannosaursintoEarth’sorbit,buttodoso,ithastoburn20timesthatweightinfueltocounteracttheforceofEarth’sgravity.Whileyoudon’thavetoexertthatmuch
energytohoistyourselfoutofbed,munchonsomeCheerios™,andcatcharidetoschool,youreverydayactivitiesandthelaunchofarocketallinvolveenergyexpendedtoovercomeorgenerateforcesthatresultinmotion.Physical sciencestudiestherelationshipsbetweenmotion,forces,energy,andtherulesoftheirinteraction.
Todiscovertheserulesofinteraction,scientistsspendalotoftimetakingcarefulmeasurements.Asyoumayalreadyknow,scientistshaveagreedtousemetricunitsofmeasurementssothatscientistsallovertheworldcaneasilymakecomparisons.Those 6.6 tyrannosaurs, by theway,weigh30,000 kilograms(kg),or10,000pounds. Whenwethinkaboutthemorningdrivetoschool,wethinkoftheearthasastationary,ornon-moving,object.Foreverydayactivities, theearthservesasour frame of reference for themotionsandforceswithwhichwedeal.Butwecertainlycould(and sometimes must) consider other frames of reference inphysical science.The earth rotates on its axis at the rate of1,650 kilometers per hour. less energy is required to launchaspaceshuttleinthedirectionofEarth’srotationthanagainstit,soscientistsmustexpandtheirframeofreferencetoincludeamovingEarth.For launchingashuttle intoEarth’sorbit, thesunandotherplanets in thesolarsystemcanbeconsidered
stationary.Ofcourse,weknowthattheplanetsactuallymovearoundthesun,soifweplannedajourneytoMars,forexample,wewouldhavetochangeourframeofreferenceyetagain.Wecouldconsiderthedistantstarsasourstationaryframeofreference. So,fastenyourseatbeltsandpreparetoenjoytherideaswepropelourselvesthroughauniverseofmotion,forces,andenergy.
1. Onatrainridecross-country,thetrees,buildings,andpeopleappeartobespeedingby
thewindow.Thisisbecausethetrainisour .
2. Scientistsusethe systemformakingmeasurements.
3. Physical science studies the relationships between ,
,and .
4. If6.6tyrannosaursweigh30,000kg,thenwhatdoesoneweigh?
Wanttogiveonealift?
5. Formostactivities,the makesahandyframeofreference.
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Part 1: Measuring Tools—Meet the Metric System
Our English system of weights and measures has a colorfulhistory, including a length measurement called the foot based ontheshoesizeofakingandan inchdefinedas the lengthof three
barleycornsplacedendtoend.ButEnglishmeasurementscanbeconfusinganddifficulttoconvertintodifferentunits.Scientistsuseametric systemofweightsandmeasurescalledSysteme International d’Unites (SI for short), basedonunitsoften. Thebasicunitoflengthisthemeter,whichisslightlylongerthantheEnglishyard.Prefixesareaddedtoindicatemeasurementsthatincreaseordecreasebyafactoroften.So,adecimeteris0.1m(theprefixdeci meansone-tenth),acentimeteris0.01m(centimeansone-hundredth),andamillimeteris0.001m(millimeansone-thousandth).Toconvertfromonemeasurementtoanother,yousimplymoveadecimalpoint.Ifsomethingmeasures360cm,calculatethenumberofmetersbymovingthedecimalpointtwoplacestotheleft,i.e.,360cm=3.60m. Going in theotherdirection,onedekameter is10m(dekameans ten),ahectometer is100meters(hectomeansonehundred),andakilometer is1,000meters(kilomeansonethousand), i.e.,1km=0.6miles.Thesameprefixesareusedforallmetricunits.Otherprefixesincludemicro(one-millionth)andmega(onemillion).Amicrosecondisone-millionthofasecond,anda megahertzisamillionhertz(seepage35). AsinEnglish,secondsandhoursareusedtomeasuretime.Until1956,thesecondwasdefinedintermsofafractionofthemeansolarday,butthedaylengthisslowlyincreasingastheearth’sspinslows.Thesecondisnowdefinedasthetimeittakesacesium-133atomtomake9,192,631,770vibrations! Thebasicmetricunitofvolumeistheliter,approximatelyaquart.Aliterisalsoequalto100mm3(cubicmillimeters).Areaismeasuredinsquaremeters(m2).1m2isapproximatelythesurfaceareaofacardtable.Massismeasuredingramsandkilograms.1,000kg=1metricton,whichisnearlythesizeofanEnglishton.Forceismeasuredinnewtons,with1newtonbeingaboutone-fifthofapound. Thejouleistheofficialunitofenergy,definedastheamountofworkdonebyaforceofonenewtonactingoveradistanceofonemeter. Temperature is measured in degrees Celsius (°C), instead of degrees
Fahrenheit(°F).Thefreezingpointofwateris0°Cand32°F.°C = °F – 32 x %l;°F =
(°C x(g) + 32. Thetheoretical temperatureatwhichatomscannolongermove(willhavenomorekineticenergy)iscalled0 K(pronouncedzeroKelvin).Thisisalsocalledabsolute zero.Waterboilsat373Kelvin(theword“degrees”isnotused.)
Part1:MeasuringTools—MeettheMetricSystem
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Measuring With Metrics
Somecommonmetricconversionsarelistedbelow:Refertothistableasnecessarywhensolvingproblemsinthisworkbook.
1squaremeter(m2)=10.764squarefeet(ft.2) 1meter(m)=3.28feet(ft.) 1squarefoot(ft .2)=0.093squaremeters(m2) 1millimeter(mm)=0.039inch(in.) 1squarekilometer(km2)=0.386squaremile(mi.2) 1inch(in.)=25.4millimeters(mm) 1cubicfoot(ft.3)=0.028cubicmeter(m3) 1yard(yd.)=0.914meters(m) 1squaremile(mi.2)=2.59squarekilometer(km2) 1mile(mi.)=1.609kilometers(km) 1cubicmeter(cm3)=35.315cubicfeet(ft.3) 1kilometer(km)=0.621miles(mi.) 1cubicinch(in.3)=16,387.064cubicmillimeters(mm3)1hectare(ha)=2.471acres(ac.) 1liter(l)=1.057quarts(qt.)=0.264gallons(gal.) 1acre(ac.)=0.405hectares(ha) 1gram(g)=0.035ounces(oz.)[avoirdupois] 1quart(qt.)=0.946liter(l) 1kilogram(kg)=2.204pounds(lbs.)[avoirdupois] 1ounce(oz.)=28.35grams(g) 1newton(N)=0.2248pounds(lbs.) 1pound(lb.)=0.454kilogram(kg) 1pound(lb.)=4.448newtons(N) Inaddition,1lofwaterweighs1kg;1ml=1,000mm3andweighs1gram.1cubicmeter(m3)ofwaterweighs1metricton.1cubiccentimeterisaboutthesizeofasugarcube.Sometimescubiccentimeters(cm3)arereferredtoas“cc.”1cm3=1cc
Directions: Usethemetricrulerprintedonpage3,theconversiontableabove,andanyotherinformationprovidedonpages3and4tohelpanswerthequestionsbelow.
1. Measurethelengthofyourindex(pointing)fingerfromitstiptoitsknucklejoint.Record
thelength,firstincentimeters,theninmillimeters. cm mm
Now,ifyoueverforgetyourhandyrulerandneedtomeasuresomething,youcanuse
thefingeronyour“handyhand”todosoandfigureouttheactuallengthlater.
2. Howtallisthispageinindexfingerunits?(Youmayhavetoguessafractionofafinger
unittocompletethemeasurement.) fingerunits.Whatisthisincentimeters?
cm
3. Thegraduatedcylindertotherightcontainshowmanymillilitersof
water?(Eachmarkrepresents0.5ml.) ml
4. You’refishingatyourfavoritelakeinJuly.Thethermometersaysthe
temperatureis93°F.What isthetemperatureindegreesCelsius?
(tothenearestdegree) °C
5. Howmanytonsissixmegatons?
6. Convertallofthefollowinglengthstomillimeters. A.12cm= mm B.5inches= mm C.1yard= mm D.1meter= mm E.10feet= mm
MeasuringWithMetrics
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Part 2: The Mechanics of Motion— Measuring Speed and velocity
“Move it!”saysDad,andyouknowyoumustchangeyourposition inatimelymanner—which isprecisely thedefinitionofmotion.Thespeedwithwhichyoumovemost likelydependson the loudnessofDad’sbark.Speed equals the distance traveled(insomemetricmeasureoflength,likemeters)
divided by the time it takes to move that distanceinsecondsorhours:s = d/t.Bymultiplyingbothsidesofthisequationbyt,youwillalsoseethatthedistancetraveled(d)equalsspeed(s)timestime(t).(d = st). If you want to look cool, you might move at aconstant speed—that is, you move the same distanceduringeachintervaloftimemeasured.Ifyougraphdistancemovedagainsttime,yougetastraightlineliketheoneattheright.
Ifyourcoolnesstakestimetogather,youmightmovequicklyatfirst,thenslowdown.Agraphmightlookliketheoneattheleft.
Thespeedatwhichyoumoveatanygivenmomentisyourinstantaneous speed.Youraverage speedequalsthetotaldistancetraveledoverthetimeintervalmeasured.(Averagespeedandinstantaneousspeedarethesamewhenspeedisconstant.) velocity is speed in a particular direction.DoesDadwantyoutocometohimormoveaway?velocitycanberepresentedbyanarrowcalledavectorwhoselengthisdeterminedbythespeedmoved.Thesevectorscanbeaddedorsubtracted.(FirstyoumoveawayfromDad,andthenyouchangeyourmindandmovecloser.)
Part2:TheMechanicsofMotion—MeasuringSpeedandvelocity
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1. Whatisthespeedofacartraveling144kmin90minutesinkilometersperhour?
km/hInmilesperhour? mph
2. IfMarvinrunsataspeedof16km/h,howfarwillhetravelin45minutes? km
3. lookatthegraphbelowthatmeasuresthespeedofarabbitoverthecourseofanhour.
Whatistherabbit’sinstantaneousspeedat30minutes? m/min
Whatisitsaveragespeedfortheentirehour?
m/min
4. Indicate which of the following are speeds
andwhicharevelocities:
A.125cm/sec
B.30km/hnorthwest
C.350m/secnorth
D.520km/h
5. let1cm=200km/h.Inthespacebelow,drawavectorthatrepresentsthenetvelocityof
aplanethattravels300km/hnorth,175km/hsouth,then225km/hnorth.
Part 2: The Mechanics of Motion: Measuring Speed and velocity (cont.)
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Part2:TheMechanicsofMotion:MeasuringSpeedandvelocity
Get Ready, Get Set, Accelerate!
Thestarter’sgunfires.Yourthighstightenasyouboltfromtheblocks.Yougofromastandstill(0velocity)towarp4(orsoitfeels)injustafewseconds.In other words, you have changed velocities, or accelerated. Acceleration (a) equals final velocity (vf) minus original velocity (vo) divided by time
(t) elapsed.a = (vf – vo)/t. Notethatbecauseaccelerationinvolvesvelocity,itisavector.Youdon’tjustspeedup,youspeedupmovingtowardthefinishline.Note,too,thatyourbodyfeelsanychangeindirectionandvelocity,whetheryouareinarace,slammingonthebrakesinacar,orscreamingasyourrollercoastercarinvertsduringthemonsterloop. So,let’ssayyouacceleratefrom0m/secto3m/secin1second.Acceleration=(3m/sec–0m/sec)/1secor3m/sec/sec.Inotherwords,ifyoumaintainthatacceleration,yourvelocitywillincrease3m/secforeverysecondthatpasses.Attwoseconds,velocitywouldbe6m/sec,at3seconds,velocityequals9m/sec,andsoforth.Graphsofaccelerationarealwayscurvedlines. Ichabodwasfasteroutof theblocks,butnowhisacceleration is decreasing. Negative acceleration iscommonlycalleddeceleration.YouleaveIchabodinthedust.Thefinishlinebeckons.Butthenyoufeelaswooshofairandsmellahintofperfume.Beatricepassesyou.Wheretheheckdidshecomefrom? Yourmomisrotatingherarminacircle,urgingyouon.Herarmisaccelerating,too.Although the speed of her circles remain the same, the direction of motion of her arm is constantly changing,meaning thevelocityofherarm ischangingeverymoment—theverydefinitionofacceleration. Can’tdisappointMom.YoubeatBeatricebyanose.
1. Usingtheabovegraph,howfarhasthesprinterrunafter5seconds? After8
seconds? .Whatishervelocityat5seconds? At8seconds?
Whatisheraccelerationbetween5and8secondsintotherace?
(Makesureyougiveallanswersintheproperunits.)
2. Acarisstoppedatastoplight,butfoursecondslateristraveling35km/h.Whatisthecar’s
acceleration?
3. Youaresittingonthecouchwatchingcartoons.Relativetotheearth,areyouaccelerating?
Relative to the sun, are you accelerating? Explain your answer.
4. Arunnerwhopullsahamstringandhastoslowdownis:
A.Negativelyaccelerating.B.Accelerating.C.Decelerating.D.BothAandC.
GetReady,GetSet,Accelerate!
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Conserving Mother Mo(mentum)
136-kg lineman Duane Dunsmore picks up a fumbleand heads toward the goal line. He knocks 91-kg RockNewtononhiskeisterandscoresatouchdown.Dunsmore’s
team,still behind,begins toplayharder.Theother teambegins tomakemoremistakes.Asportscastersays“MotherMohasshifted,”meaningthatthegame’smomentumhasshifted. Physicalscientistsdefinemomentuminaspecificway:Momentum equals mass (m) times velocity (v). Momentum = mv. So, if mass ismeasuredinkilogramsandvelocityinmeterspersecond,momentumhastheunitskg-m/sec. IfDunsmorewasmoving3meters/secwhenhehitNewton,whatwasDunsmore’smomentum?136kgx3m/sec=408kg-m/sec.IfNewtonwasrunningthesamespeed,whatwashismomentum?ButwhatifNewtonwasrunningfaster?IfNewtonhadbeenrunning5m/sec,hismomentumwouldhavebeen455kg-m/sec,andhecouldhavestoppedDunsmore,eventhoughhewas lighter.Bulletshavesmallmasses,buttheycancreategreatdamagebecausetheirvelocityissohigh.Glaciersmaycreepalongatcentimetersperyear,buttheirmassesaresohuge,theycaneasilyplowdownentireforests. Foragivensetofobjects,the total momentum stays the same unless some outside force acts on those objects.Momentum is conserved(staysthesame)forthatsetofobjects.WhenDunsmoredeckedNewton,themomentumDunsmorelostwastransferredtoNewton.
1. Whatisthemomentumofa0.35-kgblackbirdflyingat20m/sec? (Alwaysgivetheunitsinyouranswer.)
2. Whichobjecthasmoremomentum:ataxitraveling11km/horabaseballpitchedat150km/h?Explainyouranswer.
3. WhatspeedwouldRockNewtonhavehadtobemovingjusttocounteractthemomentum
ofDuaneDunsmoremovingat3mpersecond? m/sec4. Momentumistheproductofanobject’s and .5. Katieweighs68kg,andRoxanneweighs45kg.Botharelongjumpersatatrackmeet.What
isRoxannegoingtohavetodotojumpfartherthanKatieatthemeet?
6. Placethefollowingobjectsinthecorrectorderfromhighesttolowestmomentum,assumingthattheyareallmovingattheirtopspeed:fly,spaceshuttle,bullet,volkswagen,freighttrain.
7. Whenabowlingballhitsthepinsattheendofthebowlingalley,whathappenstotheball’s
momentum?
ConservingMotherMo(mentum)
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AFeelingforForces
F1
F2
F4
F3
Net Force = F1 + F2 + F3 + F4
= 4 + 5 + 2 + 3 = 10
Vector 1 :
Vector 2 :
Vector 3 :
Vector 4 :
A Feeling for Forces
Yoursisterfallsdown.Apowerfulmagnetinajunkyardmovesscrapmetal.Theschoolbusstopstopickyouup.Whatisresponsibleforthesemotions?Forces.Scientificallyspeaking,forces are any kind of a push or pull(includingnudges
andsucks).Gravitymayhavecausedyoursistertofallasitpulledonherunbalancedmass—oryoumayhavepushedher.Magneticforcespulledonthemetalbodyofanoldcar.Thefrictionalforcesofbrakepadstouchingwheelsstoppedthemotionoftheschoolbusinfrontofyourhouse. A force gives energy to an object, either causing it to move, stop, or change direction. Intherealworld,manyforcesmayactonanobjectatthesametime.Gravitytugsatyoursister.Windpushesagainstherbody.Butonlyanunbalanced forcecomingfromaparticular directionwillcausehertofalldown.Becauseforceactsinaparticulardirection,itisavectorlikevelocityandacceleration.Youcanthinkofforcesasarrowswhoselengthindicatesmagnitudeoramountandwhosearrowheadpointsinthedirectioninwhichtheforceisacting.Forcescanbeaddedtogethertogetalargerforceorsubtractedfromeachothertomakeasmallerforce.
Nomotionresultsfromtheactionofbalanced forces.Ifyouandyourbrotherpushequallyhardonyoursisterfromoppositedirections,shewon’tmove(althoughshewillcomplain). Weoften take frictional forces forgrantedbecause theyaresocommon.Frictionalforcesareforcesthatactinadirectionoppositetomotion.Theyarecausedbytinyirregularitiesinsolidsurfacesthatslidepastoneanotherasinthecaseofslidingorrolling friction(asinbrakesandrollerskates)andthe impactof themoleculesofa liquid in thecaseoffluid friction.Fluidfrictionisusuallyasmallerforcethanslidingorrollingfriction,whichiswhythemovingpartsofenginesaregreased.
1. Forcesareanykindofa or .2. TorF?Forcesalwaysresultinmotion.3. lookat thefollowingforcevectors.Measuretheir length incentimeters,andnotetheir
directions.Onyourownpaper,drawonevectorthatrepresentsalloftheseforceswhentheyareaddedtogether.
4. Indicatethekindoffriction(sliding,rolling,orfluid)representedinthefollowingexamples:A.Arunnerslidingintosecondbase:
B. Agirlgoingdownawater-filledslideatanamusementpark: C. Pedalingabicycle:
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Newton’s Big 3
“Newton who? Big 3 what?” you might ask. Sir Isaac Newton (1642–1727)isconsideredbysometobethesmartestpersonwhoeverlived—supernerd#1.Althoughthatopinioncanbedebated,Newtondiddiscoverandinvent
manythingsduringhislifetime,includingthree lawsthatsummarizetherelationshipofforcesandthemotionofobjectsforallthingsintheuniverse(withafewminormodificationsunderexceptionalconditionsdiscoveredbyAlbertEinsteinsometimelater.)
Newton’s First Law:Anobjectatrestwillstayatrest.Anobjectthatismovingwillkeepmovingataconstantvelocityunlessanunbalancedforceactsonit. Pushyouremptydesk.Itmoves,thenstops.Why?Frictionalforcesactinthedirectionoppositetoyourpush.Ifyouputwheelsunderyourdesklegs,itmovesfartherwiththesamepush—lessfriction.Iftherewerenofrictionorotherforces(likeawallattheothersideof theroom)actingagainstyourpushforce, thedesk
wouldmoveforever.Thistendencytokeepmovingiscalledinertiaanddependsonthemassoftheobject.Achairwillmovefasterwiththesamepushthanthedesk.Thedeskhasmoremass,andthusmoreinertia. NotethattheFirstlawstatesthatanobjectwillmoveataconstant velocityunlessanunbalanced forceactsonit.Whenanunbalancedforceactstochangeanobject’svelocity(directionand/orspeed),thatobjecthasbeenaccelerated (seepage7).ThisleadstoNewton’s Second Law: Theforceneededtomoveanobjectisequaltotheproductofthatobject’smassandacceleration.Writtenasanequation,it isF = ma.Theunitofforce,honoringSirIsaac,iscalledanewton. In themetricsystem,onenewtonof force isneeded toaccelerateonekilogramofmassattherateofonemeterpersecondpersecond(1N=1kg-m/sec/sec).Ifyoukeepaccelerationconstant,youcanseethat it takesmoreforce(andthusmoreenergy)tomovethemassofatruckthanamotorcycle. Newton’s Third Law:Foreveryaction,thereisanequalandoppositereaction.Throwaheavyballawayfromyou,andthislawmaynotbeobvious,becauseyouareusedtodealingwiththeforceoffrictionofyourfeetagainsttheground.Dothesamethingwhilestandingonaskateboard,andyouwillcertainlynoticetheskateboardmovingintheoppositedirectionfromyourthrow.Thesamethingwillhappenifyousteptooquicklyfromanunanchoredboattothedock.Youcouldgetwet,ifyou’renotcareful.
1. Whatistheforceinnewtonsneededtomovea1,500-kgvehicleatanaccelerationof3
m/sec/sec?
2. Whichhasmoreinertia,a150-kgsumowrestlerora100-kgaccountant?
3. HowdoesabirdflyingillustrateNewton’sThirdlaw?
Newton’sBig3
Answer Keys
AnswerKeys
A Universe of Motion, Forces, and Energy (Page 2)1.frameofreference;2.metric;3.motion,forces,energy(anyorder);4.4,545.5kg;5.earth
Part 1: Measuring Tools: Measuring With Metrics (Page 4)1.variableanswers;2.variableanswers;3.51.5;4.34;5.6million;6.A.120;B.127;C.914.4;D.1,000;E.3,048
Part 2: The Mechanics of Motion: Measuring Speed and velocity (Page 6)1.96;59.7;2.12;3.1.67m/min,1.5m/min;4.A.Speed;B.velocity;C.velocity;D.Speed;5.vectorwillbe1.75cmlong(350km),pointingnorth.
Get Ready, Get Set, Accelerate! (Page 7)1.45m,108m,15m/sec,24m/sec,3m/sec/sec;2.8.75km/sec/sec;3.No,Yes.Earthisrotatingandrevolvingaroundthesun.4.D.
Conserving Mother Mo(mentum) (Page 8)1.7kg-m/sec;2.Taxi,becauseitweighssomuchmorethanabaseball.3.4.5m/sec;4.mass,velocity(anyorder);5.Runfaster.6.Spaceshuttle, freight train,volkswagen, bullet, fly; 7. Most of it istransferredtothepins.
A Feeling for Forces (Page 9) 1.pushorpull;2.F;3.vector4centimeterslongpointingright;4.A.Sliding,B.Fluid,C.Rolling
Newton’s Big 3 (Page 10)1.4,500N;2.Thewrestler;3.Theforceofitswingbeatagainstairpropelsthebirdforward.
Free Fa-a-all and Gravity (Page 11) 1. 29.4 m/sec; 2. Itdecreases rapidly because force decreases by the inversesquare of the distance between objects. 3. Weight willdecrease;masswillstaythesame.
Forces in Fluids (Page 12) 1. The ship’s overall density(including the density of the air-filled hull) is less than thedensityofanequalvolumeofwater.2.Airmassesflowfromareasofhighpressure toareasof lowpressure,producingwind.
Work and Power (Page 13) 1.joules;watts;2.variable;3.Divideworkby10;divideworkby4;4.AandCarework;5.1,000,000watts;6.F
Part 2: The Mechanics of Motion: Putting It All Together (Page 15)CONTENT: 1. distance, time, direction; 2. T; 3. The totalmomentum (mv) of a group of objects remains the same,althoughitmaybetransferredamongobjectsinthegroup;4.vectors;5.F=ma;6.A.7.Bernoulli’s;8.W=Fd,P=W/timeorworkequalsforceusedtomoveanobject;powerequalshowfastworkhappens;9.simplemachinesCONCEPT: 1.Severaldifferentwedges;2.Theforceusedtomovethegroceriesisperpendiculartothegroceries;3.Thetimeittook.
4.Thesecondperson’saveragespeedwasgreaterthanthefirstperson’sconstantspeed;5.It takesawhiletoslowthemomentum of large objects; 6. Gravity, air movements; 7.Answerswillvary.
Part 3: All About Energy: Energy, Let Me Count Its Forms (Page 16) 1.A.Chemicalenergy;B.Nuclearenergy;C. Electromagnetic energy; D. Heat energy; E. Mechanicalenergy;2.sun;3.theabilitytodowork
Kinetic Energy: The Energy of Motion (Page 17) 1.Kineticenergyincreaseswiththesquareofvelocity;2.work;3.22,500J;4.Momentum=mvandhasdirection;K.E.=mv2/2andisnotavector;5.potential,kinetic(anyorder);6.F
Potential Energy: The Energy of Position (Page 18) 1.position;2.F;3.2,058,750J;4.6,669,000J;5.B.;6.heightandweight(anyorder)
Energy Conversions (Page 19) 1. chemical, heat,mechanical;2.energyconversions;3.Mechanicalenergyofwater,mechanicalenergyofmovingturbines,electricenergy,mechanicalenergyofdryerfan,heatenergyofdryercoils.4.Atrelease;whenithitsthegroundandwhenitstopsrolling;justbeforethefirstbounce;5.A.solarcells;B.burningfossilfuel,amatch,etc.;C.friction
Moving Heat Around: Thermodynamics (Page 20) 1.Noconvectionorconductionofheatthroughthevacuum;noheatlossbyradiationthroughtheshinyliner.2.Thereissomelossbyconductionthroughthestopperandlid.
Conserve Energy—That’s the Law! (Page 21) 1.F;2.Fossilfuels;heat,mechanical,electromagnetic;3.Underveryhightemperatures and pressures, mass can be converted toenergy;4.heat
The Laws of Thermodynamics (Page 22) 1.600J;2.Firstlaw;3.Therearealwayssomeheatlossesinanymachine.
Entropy: A Measure of Disorder (Page 23) 1.heat;2. Somewhat disordered and chaotic; 3. Eventually, theuniversewillallbeat thesame temperature,and therewillbe no energy to do work. 4.When there is a concentratedsourceofenergy,likethesun.5.lightandotheremradiation,electricity,fossilfuels;6.C.
Part 3: All About Energy: Putting It All Together (Page 24)CONTENT:1. joules;2.C.;3.kinetic;4.weight;5.heatandlight; 6. conduction, convection, radiation (any order); 7.Energy can neither be created nor destroyed by ordinarymeans.8.theFirstlawofThermodynamics;9.FCONCEPT:1.Heatfromradioactiveelementsincreaseswithdepth;2.Potentialenergy;3.SirSeymour;hiscannonballswill
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