1) WHAT IS ONE FUN THING YOU DID OVER THE SUMMER? 2) … · 2018-08-29 · SIG FIGS IN CALCULATIONS...
28
1) WHAT IS ONE FUN THING YOU DID OVER THE SUMMER? 2) FILL IN THE BLANK: “I WONDER (ABOUT) _____.” WELCOME! PLEASE TAKE A FEW MINUTES TO ANSWER THESE QUESTIONS ON THE INDEX CARD. YOU MAY USE THE FRONT AND BACK. I WILL COLLECT THEM AT THE END OF CLASS TODAY.
Transcript of 1) WHAT IS ONE FUN THING YOU DID OVER THE SUMMER? 2) … · 2018-08-29 · SIG FIGS IN CALCULATIONS...
1)WHATISONEFUNTHINGYOUDIDOVERTHESUMMER?
2)FILLINTHEBLANK:“IWONDER(ABOUT)_____.”
WELCOME!PLEASETAKEAFEWMINUTESTOANSWERTHESEQUESTIONSONTHEINDEX CARD.YOUMAY
USETHEFRONTANDBACK.IWILLCOLLECTTHEMATTHEENDOFCLASSTODAY.
WELCOMETOGENERALPHYSICS!
GOALSFORTODAY
• Answerthequestion”Whatisphysics?”• Gooverclassroomexpectations• Introducesomebasicstophysics• Doyourfirstphysicsproblem!
WHATISPHYSICS?
• Abranchofsciencethatexploresthefundamentalprinciplesonwhichourworldisbuilt.• Physicsallowsustomakeconclusionsaboutandpredictionsofwhatwecannotseebasedonwhatwecansee.
HOWDOESPHYSICSMATTER?
• Ifyouliveinthisworld,physicsverylikelyappliestoyou!• Youwillbeabletoask,answer,andeffectivelyexplainsome(possibly
silly) questionslike:• DoesAshKetchumfromPokemon havesuperstrength?• HowmuchForcedidYodausetolifttheX-WinginEmpireStrikesBack?• Howdoyouturnarocketinspace?• Islightspeedtravelpossible?• Whydoesthemoonlookhugeandyellow-ish sometimes?• …anymanyotherquestionsyoumaywonderabout!
BASICALLY,PHYSICSWILLCHANGEHOWYOUSEETHEWORLD!GETREADYBECAUSEYOURMINDWILLBEBLOWN.
GREAT,SOHERE’SHOWTOGETTHEMOSTOUTOFTHISCLASS.
• http://robertsonphysics.weebly.com/• Mostofall,askquestionsandimagine!
THEMOSTFUNDAMENTALOFFUNDAMENTALSAREVIEWOFS.I.UNITS,SIGFIGS,ANDSCIENTIFICNOTATION
S.I.UNITS
• Length– meter(m)• Mass– kilogram(kg)• Electriccurrent– Ampere(A)• Temperature– Kelvin(K)• Time– second(s)• Andmorethatwe’llgooverlater
PREFIX SYMBOL EXPONENTIAL
Tera T 1012
Giga G 109
Mega M 106
Kilo k 103
Centi c 10-2
Milli m 10-3
Micro 𝜇 10-6
Nano n 10-9
Pico p 10-12
METRICPREFIXES
DONOTFORGETTOCONVERTTOS.I.!
CONVERTINGUNITS
• 1m=100cm=1000mm=0.001km• 100km/hr =?m/s
• 100 $%&'∗ 1000 %
$%∗ )&'*+,,-./ = 27.7778 = approx. 30m/s
• Payattentiontotheunitsintheproblemandtheunitsaskedforintheanswer.
SIGNIFICANTFIGURES
• Thenumberofreliablyknowndigitsinanumber
• Tellsyouhowaccuratelyyouknowanumber
• YoucansaydowntownLAisabout10milesawayvs.it’sexactly12.7milesaway
• Evenmoreaccurately,itmightbe12.733milesaway?
SIGFIGS
• 10hasonesigfig• 12.7hasthreesigfigs• 12.733hasfivesigfigs• 0.0067hasonly2sigfigs• Zerosareonlyplaceholderstoshowwherethedecimalis.
• Howmanysigfigsdoes80.0have?Why?• Howmanysigfigsdoes60.7have?Why?
SIGFIGSINCALCULATIONS
• MultiplyingandDividing• Theanswershouldonlyhaveasmanysigfigsasthenumberwiththeleastnumberofsigfigsusedinthecalculation.• Example– findtheareaofarectanglewithsides11.3cmand6.8cm
• Yourcalculatorwilltellyou76.84cm2,butthereisnowayyouknowtheareaofthatrectangleto0.01cm2.
• Howmanysigfigsshouldyouranswerhave?
SIGFIGSINCALCULATIONS
• Addingandsubtracting• Theanswercancontainnomoredecimalplacesthantheleastaccuratemeasurement.• Example:youtiea30.6mropetotheendofa0.57-longrope.Howlongarethetworopestogether?
• Youwillget31.17m,butroundoffto31.2m
SCIENTIFICNOTATIONANDCALCULATIONS
• Insteadofwriting1,540,000m,write1.54𝑥10+𝑚• Sidenote– howmanykmisthis?
• 1.54𝑥10+𝑚x )CD),ED
= 1.54x10*m• Insteadof0.0000448kg,write4.48𝑥10FG𝑘𝑔• Sidenote– howmanygisthis?
• 4.48𝑥10FG𝑘𝑔𝑥 ),EJ$J
= 4.48𝑥10FK𝑔
DISTANCEVS.DISPLACEMENT–YOURFIRSTPHYSICSPROBLEM
5.1km
3.6km
3.2km
Yourhouse
Coffeeshopofchoice
LCHS
Whatwasthetotaldistanceofyourtrip?
= 5.1 + 3.6 + 3.2 = 11.9𝑘𝑚
DISTANCEVS.DISPLACEMENT
5.1km
3.6km
3.2km
Yourhouse
Coffeeshopofchoice
LCHS
? km
Whatisthedistance betweenyourhouseandLCHS?
Whatisthedirection betweenyourhouseandLCHS?
3.6K + 1.9K� = 4.0706𝑘𝑚 → 4.1𝑘𝑚
𝑡𝑎𝑛F)(3.6/1.9)=62°𝐸𝑎𝑠𝑡𝑜𝑓𝑆𝑜𝑢𝑡ℎ
Yourdisplacementis4.1km62° EofS(or28°SofE)
Afteryoudoaphysicsproblem,ask– doesmyanswermakesense?
• Turntoyourpartnerandcomeupwithaonesentencedifferencebetweendistanceanddisplacement.
PointA PointB
5.1km
3.6km
3.2km
Yourhouse
Coffeeshopofchoice
LCHS
4.1km
62°
Distance=11.7km
SCALARVS.VECTOR
• Scalarshaveonlymagnitude• Distanceisascalar
• Vectorshavebothmagnitudeanddirection• Displacementisavector
SOMEPRACTICEPROBLEMS
Sallyrunstwicearounda400mtrack.Whatishertotaldistance?
a) 400mb) 800mc) 600md) Noneoftheabove
Sallyrunstwicearounda400mtrack.Whatishertotaldisplacement?a) 0mb) 800mc) 400md) Noneoftheabove
SOMEPRACTICEPROBLEMS
SOMEPRACTICEPROBLEMSBillyskateboardsfor6.7meters,thenanother0.5meteruparamp,thencoasts2.0metersbackwards.
a) DrawadiagramofBilly’smotion.
b) Whatishisdistancetraveled?
c) Whatishisdisplacement?
SOMEPRACTICEPROBLEMS
Whatis[3.0x10-3][2.0x105]?Makesuretohavethecorrect#ofsigfigs.
SOMEPRACTICEPROBLEMS
Whatis4.50x109 ?Makesuretohavethecorrect#ofsigfigs.6.636x10-5
CURBYOURINTUITION
• Establishnewpointsofreferenceforyourbrain• Importanttoevaluatewhetherornotyouranswersmakesense• Insteadofsaying“1.8m/sisabout4mph”,say“that’saboutjoggingspeed”
CURBYOURINTUITIONTemperature Length/height/distance Mass Speed
60℃ record highonearth 1cmWidthofmicroSD 3g PeanutM&M 1.4m/sWalking
45℃ HeatwaveinDubai 3.5cmlengthof 3DSgame
100gcellphone 1.8m/sJogger
35℃ Pretty grossout 12cmCDdiameter 500gBottled water 4.3m/s Bikingspeed
30℃ Beachday 75cmwidth ofCaptainAmerica’sshield
1.5kg Chromebook 11m/s SchoolZone
25℃ Roomtemp80cmdoorwaywidth 2.8kgphysicstextbook 36m/s LAdriveronfreeway
0℃ Snow 1m lightsaberblade 4kg Cat 89m/s Nascar speed
-10℃ Coldday (Moscow) 229 cmheightofYaoMIng
60kg Lady 257m/s Cruisingplane
-40℃ Spitfreezes 3m 1 storybuilding 70kg Dude 340m/s speedofsound
-50℃ lowforMinnesota 5m lengthofcar 460 kgSnorlax 3.0𝑋10a𝑚/𝑠speedoflight
