Mastering Astronomy Assignment 2 PDF

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4/4/2017

Assignment 3

Assignment3 Due:5:00pmonTuesday,January31,2017 Youwillreceivenocreditforitemsyoucompleteaftertheassignmentisdue.GradingPolicy

PrelectureReadingQuestionS3.01

PartA Einstein'sgeneraltheoryofrelativitysuggeststhatgravityis______. ANSWER:

aforceofattractionthatactsatadistancebetweentwomasses oneoffourfundamentalforcesinnature causedbycurvatureofspacetime F≡GM1M2/d2

Correct

PrelectureReadingQuestionS3.02

PartA Einstein'sequivalenceprinciplesaysthat______. ANSWER:

someonetravelingat0.9cwillageatthesamerateassomeoneat0.99c theeffectsofgravityareexactlyequivalenttotheeffectsofacceleration allpeopleseethemselvesatanequivalentdistancetothecenteroftheuniverse everyonemeasuresthespeedoflighttobeequivalent

Correct

ProblemS3.27 Choosethebestanswer.

PartA Theequivalenceprincipletellsusthateffectsofthesetwothingsareindistinguishable: https://session.masteringastronomy.com/myct/assignmentPrintView?assignmentID=1714974

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ANSWER: spaceandtime. gravityandacceleration. gravityandcurvatureofspacetime.

Correct

PrelectureReadingQuestionS3.04

PartA Whatisspacetime? ANSWER:

timethatwemeasurewhentravelinginspace awayofviewingbooksatdifferentangles theinseparablecombinationofspaceandtime agraphwithfouraxes

Correct

PrelectureReadingQuestionS3.06

PartA WhichofthefollowingcorrectlydescribeswhatwemeanbyagreatcircleonthesurfaceofEarth? ANSWER:

anycirclewhosecenterisatthecenterofEarth acircleoflongitude anycirclelargerthan10,000kmindiameter anycircleoflatitude

Correct

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Assignment 3

ProblemS3.28 Choosethebestanswer.

PartA ThesurfaceofEarthhas_____dimensions: ANSWER:

one two three

Correct

ProblemS3.30 Choosethebestanswer.

PartA Youknowthatyouarefollowingthestraightestpossiblepaththroughspacetimeif ANSWER: youarestandingstill. youaremovingdirectlyfromoneplacetoanother. youareweightless.

Correct

PrelectureReadingQuestionS3.10

PartA WhichofthefollowingcorrectlydescribestherelationshipbetweenNewton'stheoryofgravityandgeneralrelativity? ANSWER:

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Assignment 3

Newton'stheoryofgravityisnowknowntobefalse,andwewerepreviouslymisledtothinkitwastrueby measurementerrors. Newton'stheoryofgravityisanapproximationtogeneralrelativitythatworkswhengravityisrelativelyweak,but breaksdownwhengravityisstrong. Generalrelativityappliesatthesubatomiclevel,butNewton'stheoryofgravitydoesnot. Newton'stheoryofgravityandgeneralrelativitygivethesameanswers,buttheformertellsustothinkofgravity asaforceandthelattertellsustothinkofgravityascurvatureofspacetime.

Correct

ProblemS3.33 Choosethebestanswer.

PartA Gravitationallensingoccursbecause ANSWER:

gravitycauseslighttoslowdown. gravitycurvesspaceandlightalwaysfollowsthestraightestpossiblepaththroughspace. theeffectsofgravityareindistinguishablefromtheeffectsofglasslenses.

Correct

ProblemS3.31 Choosethebestanswer.

PartA Accordingtogeneralrelativity,EarthgoesaroundtheSunratherthanflyingstraightoffintospacebecause ANSWER: initsownreferenceframe,Earthcanconsideritselftobestationary. Earthisgoingasstraightaspossible,buttheshapeofspacetimemakesthispathgoroundandround. gravitycreatesaninvisiblebondholdingEarthandtheSuntogether.

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Assignment 3

Correct

Supplement3Question1

PartA WhatdowemeanbythestraightestpossiblepathbetweentwopointsonEarth'ssurface? ANSWER: apaththatcrossestheequator theshortestpathbetweenthetwopoints apaththatactuallyisaperfectlystraightline apaththatfollowsacircleoflatitude apaththatfollowsacircleoflongitude

Correct

Supplement3Question3

PartA Whatdoestheequivalenceprinciplesay? ANSWER:

Youcannotdistinguishbetweenmotionatconstantvelocityandweightinagravitationalfield. TheeffectsofrelativityareexactlyequivalenttothosepredictedbyNewton'slawsofmotion. Allobserversmustalwaysmeasurethesame(equivalent)weightsformovingobjects. Theeffectsofgravityareexactlyequivalenttotheeffectsofacceleration. Gravityisthesamethingascurvatureofspacetime.

Correct

Supplement3Question5 https://session.masteringastronomy.com/myct/assignmentPrintView?assignmentID=1714974

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Assignment 3

PartA Alisfloatingfreelyinherspacecraft,andyouareacceleratingawayfromherwithanaccelerationof1g.

Howwillyoufeelinyourspacecraft? ANSWER:

YouwillfeelthesameweightasyoudoonEarth. Youwillfeelweight,butmorethanonEarth. Youwillfeelyourselfpressedagainstthebackofyourspaceshipwithgreatforce,makingitdifficulttomove. Youwillfeelweight,butlessthanonEarth. Youwillbefloatingweightlessly.

Correct

Supplement3Question6

PartA Alisfloatingfreelyinherspacecraft,andyouareacceleratingawayfromherwithanaccelerationof1g.

Supposeyouclaimthatyouarefeelingtheeffectsofagravitationalfield.HowcanyouexplainthefactthatAlisweightless ANSWER:

Sheisweightlessbecausesheisinfreefall. Ifyouareinagravitationalfield,thenshecannotbeweightless. Sheisweightlessbecausesheisinafreefloatframe. Sheisweightlessbecausesheismovingatconstantvelocity.

Correct

Supplement3Question7v2   https://session.masteringastronomy.com/myct/assignmentPrintView?assignmentID=1714974

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Assignment 3

PartA Imaginethatyouaresittinginaclosedroom(nowindows,nodoors)when,magically,itisliftedfromEarthandsent acceleratingthroughspacewithanaccelerationof1g(9.8m/s2).AccordingtoEinstein'sequivalenceprinciple,whichofthe followingistrue? ANSWER:

Youwon'tfeelanychangeandwillhavenowaytoknowthatyou'veleftEarth. You'llknowthatyouleftEarthbecauseyou'llbefloatingweightlesslyinyourroom. You'llknowthatyouleftEarthbecausewhenyoudropaballitwillfallsideways. You'llfeelaforcethatwillcauseyourheadtorepeatedlybangintotheceiling.

Correct

Supplement3Question13

PartA Whichofthefollowingcorrectlydescribestheconditionsunderwhichyouwillfeelweightless,accordingtogeneralrelativity ANSWER:

anytimeyourworldlineisfollowingthestraightestpossiblepaththroughspacetime Youcanneverbetrulyweightless. anytimeyourworldlineisperfectlystraight anytimeyouaretravelingthroughspaceatconstantspeed anytimeyouareveryfarfromanyplanet

Correct

Supplement3Question15

PartA Accordingtogeneralrelativity,whydoesEarthorbittheSun? ANSWER:

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Assignment 3

ThemysteriousforcethatwecallgravityholdsEarthinorbit. Earthisfollowingthestraightestpathpossible,butspacetimeiscurvedinsuchawaythatthispathgoesaround theSun. EarthandtheSunareconnectedbya"ropelike"setofinvisible,subatomicparticles.

Correct

Supplement3Question21v2  

PartA FigureS3.20ainthetextshowsaphotographthatappearstoshowfouridenticalgalaxiesarrangedasacross.Whatarew reallyseeing? ANSWER: fourimagesofasinglebackgroundgalaxy,createdbythegravitationallensofamassiveforegroundgalaxyor cluster fourgalaxiesthatarenearlyidenticalbecausetheywerebornataboutthesametime apicturetakenwithapoorlymadetelescope,sothatasinglelargeobjectappearsasfourfuzzydots alargegalaxywithfourcentralmassesthatglowbrightly

Correct

Supplement3Question22

PartA Whichofthefollowingisfalse? ANSWER:

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Assignment 3

Thespeedoflightslowsdownnearablackhole. Nothingcanmovefasterthanthespeedoflight. Theabsolutenessofthespeedoflightisanexperimentallyverifiedfact. Thespeedoflightinavacuumisconstant. Observersindifferentreferenceframesmeasurethesamespeedoflight.

Correct

Supplement3Question23

PartA Whichofthefollowingisfalse? ANSWER:

Theorderofeventscanbedifferentforobserversindifferentreferenceframes. Ifoneobservermeasurestwoeventstobesimultaneous,allobserversmustagreeontheirsimultaneity. Fromyourpointofview,timerunsslowerinthereferenceframeofanyonemovingrelativetoyou. Timerunsslowernearablackhole. Timedilationisanobservationallyverifiedfact.

Correct

Supplement3Question26

PartA Spaceisdifferentfordifferentobservers.Timeisdifferentfordifferentobservers.Spacetimeisthesameforeveryone. ANSWER:

True False

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Assignment 3

Correct

Supplement3Question30

PartA Althoughmanyscientistsbelievegeneralrelativitytobecorrect,thereisnoexperimentalevidencesupportingthe predictionsthistheorymakesabouttime. ANSWER: True False

Correct ScoreSummary: Yourscoreonthisassignmentis97.9%. Youreceived23.5outofapossibletotalof24points.

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