ap unit 9 suppdysoncentralne.pbworks.com/w/file/fetch/138999510/ap unit... · 2 days ago · 5. the...
Post on 18-Mar-2021
5 Views
Preview:
TRANSCRIPT
UNIT 9
Sound
APUnit9:Sound-ExamplesandTryThisProblems
Ex.1Determinethespeedofsoundinairatatemperatureof37oC.
TryThis1:Thespeedofsoundonacertaindayis343m/s.WhatisthetemperatureindegreesCelsius?
Ex.2
Ans.a)70dBb)73dBc)
TryThis2:
Ex.3
Ans.a)b)c)
TryThis3:
Ex.4
Ans.566Hz
TryThis4:
Ex.5
Ans.a)475Hzb)339Hz
TryThis5:
Ex.6
TryThis6:
Ex.7
a) b) c)
TryThis7:
Ex.8
a) b)
TryThis8:
Ex.9A certain piano string is supposed to vibrate at a frequency of 4.40 x 102 Hz. To check its frequency, a tuning fork known to vibrate at a frequency of 4.40 x 102 Hz is sounded at the same time the piano key is struck, and a beat frequency of 4 beats per second is heard. (a) Find the two possible frequencies at which the string could be vibrating. Ans. 444 Hz. and 436 Hz
TryThis9:The assistant adjusts the tension in the same piano string, and a beat frequency of 2.00 Hz is heard when the note and the tuning fork are struck at the same time. (a) Find the two possible frequencies of the string. Ans. (a) 438 Hz, 442 Hz
Unit9Problems:Sound
Video9.1-SoundasaWave,SpeedofSound,SoundIntensity,Decibels,SphericalWavesUnless otherwise stated, use 345 m/s as the speed of sound in air.
1.ThecoldestrecordedtemperatureofaironEarth,128.6°F,occurredonJuly21,1983,atVostok,aRussian
stationinAntarctica.Whatisthespeedofsoundinairatthistemperature?(Ans.272m/s)2.Agroupofhikershearsanecho3saftershouting.Ifthetemperatureis22
oC,howfarawayisthemountain
thatreflectedthesoundwave?(Ans.516m)3.Asoundwavetravelinginairat65
oChasafrequencyof845Hz.Find(a)thewavespeedand(b)the
wavelength.(Ans.a)368m/sb).436m)4.Theintensitylevelproducedbyajetairplaneatacertainlocationis150dB.Calculatetheintensityofthe
soundwavegeneratedbythejetatthislocation.(Ans.1000W/m2)5.Theareaofatypicaleardrumisabout5.0x10
-5m
2.Calculatethesoundpower(theenergypersecond)
incidentonaneardrumat(a)thethresholdofhearingand(b)thethresholdofpain.
(Ans.a)5x10-17Wb)5x10-5W)6.Anoutsideloudspeaker(consideredasmallsource)emitssoundwaveswithapoweroutputof100W.(a)
Findtheintensity10.0mfromthesource.(b)Findtheintensitylevelindecibelsatthatdistance.(c)Atwhat
distancewouldyouexperiencethesoundatthethresholdofpain,120dB?
(Ans.a).0796W/m2b)109dBc)2.82m)
Video9.2-DopplerEffect,Interference,StandingWavesonaString
7.Anairplanetravelingathalfthespeedofsound(v=172m/s)emitsasoundoffrequency5kHz.Atwhat
frequencydoesastationarylistenerhearthesound(a)astheplaneapproaches?(b)Afteritpasses?
(Ans.a)10kHzb)3.33kHz)
8.Twotrainsonseparatetracksmovetowardeachother.Train1hasaspeedof130km/h,train2aspeedof
90.0km/h.Train2blowsitshorn,emittingafrequencyof500Hz.Whatisthefrequencyheardbythe
engineerontrain1?(Ans.595Hz)9.Abatflyingat5m/sischasingainsectflyinginthesamedirection.Ifthebatemitsa40-kHzchirpand
receivesbackanechoat40.4kHz,whatisthespeedoftheinsect?(Takethespeedofsoundinairtobe340
m/s.)(NOTE:Thisisachallengingproblem!)(Ans.3.31m/s)10.Astretchedstringfixedateachendhasamassof40.0gandalengthof8m.Thetensioninthestringis
49.0N.(a)Determinethepositionsofthenodesandantinodesforthethirdharmonic.(b)Whatisthe
vibrationfrequencyforthisharmonic?(Ans.a)Nodesat0m,2.67m,5.33m;Antinodesat1.33m,4m,6.67mb)18.6Hz)11.Asteelwireinapianohasalengthof0.7mandamassof4.3x10
-3kg.Towhattensionmustthiswirebe
stretchedsothatthefundamentalvibrationcorrespondstomiddleC,frequency261.6Hz?(Ans.824N)
Video9.3-Resonance,StandingWavesinAirColumns,Beats,SoundQuality
12.Thewindpipeofatypicalwhoopingcraneisabout5.0ft.long.Whatisthelowestresonantfrequencyof
thispipe,assumingitisclosedatoneend?Assumeatemperatureof37oC.(Ans.58Hz)
13.Apipeopenatbothendshasafundamentalfrequencyof300Hzwhenthetemperatureis0
oC.(a)What
isthelengthofthepipe?(b)Whatisthefundamentalfrequencyatatemperatureof30oC?(Ans.a).552m
b)316Hz)14.Twoadjacentnaturalfrequenciesofanorganpipearefoundtobe550Hzand650Hz.Calculatethe
fundamentalfrequencyandlengthofthispipe.(Usev=340m/s.)Determinewhetherthepipeisopenatboth
endsoropenatonlyoneend.(Ans.50Hz;1.7m;Closedatoneend)
15.Twopipesofequallengthareeachopenatoneend.Eachhasafundamentalfrequencyof480Hzat300K.
Inonepipetheairtemperatureisincreasedto305K.Ifthetwopipesaresoundedtogether,whatbeat
frequencyresults?(Ans.3.98Hz)16.TheGstringonaviolinhasafundamentalfrequencyof196Hz.Itis30cmlongandhasamassof.5g.
Whilethisstringissounding,anearbyviolinistshortenstheGstringonheridenticalviolinuntilabeat
frequencyof2Hzisheardbetweenthetwostrings.Towhatlengthdidsheshortenherstring?(Ans.29.7cm)
ConceptualQuestions:Sound
1.Anautofocuscamerasendsoutapulseofsoundandmeasuresthetimetakenforthepulsetoreachan
object,reflectoffofit,andreturntobedetected.Canthetemperatureaffectthecamera’sfocus?
2.Explainhowthedistancetoalightningboltcanbedeterminedbycountingthesecondsbetweentheflash
andthesoundofthunder.
3.Asoftdrinkbottleresonatesasairisblownacrossitstop.Whathappenstotheresonantfrequencyasthe
leveloffluidinthebottledecreases?
4.Anairplanemechanicnoticesthatthesoundfromatwin-engineaircraftvariesrapidlyinloudnesswhen
bothenginesarerunning.Whatcouldbecausingthisvariationfromloudtosoft?
5.Whydoesavibratingguitarstringsoundlouderwhenplacedontheinstrumentthanitwouldifallowedto
vibrateintheairwhileofftheinstrument?
Unit9LabActivity
Inthislabactivityyourgroupwillstudyresonantfrequenciesofatubeopenatoneend.
Materials:1)PlasticTube
2)ContainerofWater
3)MeterStickorRuler
4)TuningForks
ProblemStatement:
Yourtaskistopredictthelengthoftuberequiredtocreatearesonanceforseveraldifferentfrequenciesof
tuningforks.YouwilluseagivenlengthofPVCtubingwhichmaybeimmersedinwatertovaryingdepths,
thuseffectivelycreatingatubethatisclosedatoneendwhoselengthyouareabletochange.
Using3differenttuningforks,calculatethelengthoftuberequiredtocreatearesonanceforeachone.Itmay
bepossiblethattherearetwodifferentpossiblelengthsforagiventuningfork.Inthatcase,youshouldtest
bothoftheselengths.Youwillneedtoknowthetemperatureintheroomthedayyouperformthe
experiment.
Onceyouhavemadeyourcalculations,testthembyfindingthelengthrequiredtoproducearesonancewith
eachtuningfork.Useyourmetersticktomeasurethelengthoftubeatwhichtheresonanceoccurs.Leteach
personinyourgrouptakeaturndoingthis.
AnalysisQuestions:
1)Showthecalculationsyouusedtodeterminethelengthoftuberequiredforeachofthethreetuningforks
yourgroupused.Recordthepredictedtubelengthandtheactualtubelengthinatable.
2)Discussanydiscrepanciesyounoticeinthepredictedversusactualvalues.Whyisitnecessarytoknowthe
temperaturewhenperformingthisexperiment?
PhysicsLabReportChecklistParticipantNames:____________________________________________________________Pd.______
LabTitle:_____________________________________________DueDate________________
OverallReport
Format
1.TitlePagecontainsGroupnames,Experiment
Title,DateDue,andPeriod
2.Allsectionsreportarepresent,inproperorder,
andareclearlylabeledinBoldUnderlineprint.
01
Introduction 1.Thereisaclearstatementofthe
purpose/objectiveofthelab.
2.Thereisabriefdiscussionoftherelevant
backgroundinformationandtheoryinvolvedinthe
lab.
012
012
Experimental
Procedure
1.Thereisaclearwrittendescriptionofthe
proceduresfollowedintheexperiment.
2.Thereisadiagramorpictureoftheexperiment
set-upwithcomponentslabeled.
012
012
RawData 1.Allcollecteddatafromtheexperimentis
presentedintableformorotherappropriate
format.
2.Unitsofmeasurementsareclearlyindicated.
012
01
Analysis 1.Asampleofeachtypeofcalculationneededin
theexperimentisprovidedandisdonecorrectly.
2.ResultsofcalculationsarepresentedforALLdata
intableform.
3.Graphsofdataareincluded,areneat,clearly
titled,anddisplayappropriateunitsandscales.
4.Sourcesofmeasurementerrorareindicatedand
discussed.
012
012
012
012
Conclusions 1.Finalconclusionofthelabisclearlystatedand
showsunderstandingoftheobjectiveofthelab.
2.Suggestionsforhowthelabcouldbeimproved
areincluded.(Whatwouldyouhavedone
differentlyifyouweredoingthelabagain?)
0123
012
Note:Labreportsmustbetyped,nothandwritten,withthefollowingexceptions:1)Graphsmaybedonebyhandongraphpaper.2)Samplecalculationsmaybeneatlyhandwritten.
TotalScore:________/25
Comments:
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
MultipleChoiceQuestions
1. 4.
2.
3.
6.
FreeResponseQuestions
#1.
#2.
#3.
#4.
top related