connections360安全卫士7

Whenpeoplethinkaboutstructures,theyoftenthinkabouttowersandbridges.
Whilethesestructuresareimpressive,thetruthisthateveryobjectyouencounterisastructure.
Ifyoupacksnowtomakeasnowball,youhavemadeastructure.
Ifyoucombineingredientsandbakealoafofbread,youhavealsomadeastructure.
Ifyoulookcarefullyatawidevarietyofstructures,youwillnoticethatmanyofthemhavesimilarities.
Differentstructuresmightservethesamefunction,likethestructuresinFigures4.
4and4.
5.
Inthissection,youwillexplorewaystoclassifystructures.
100UNITBStructures:FormandFunctionClassificationofStructures4.
1Hereisasummaryofwhatyouwilllearninthissection:Astructurecanbeclassifiedbyitsfunction.
Astructurecanbeclassifiedbyitsconstruction.
Astructurecanbeclassifiedasasolid,frame,orshellstructure.
B4StartingPointThinkaboutatleastsixdifferentstructuresthatyoucanuseasaseat.
Makealistofthem.
Somecanbeindoors,somecanbeoutdoors.
WhataretheadvantagesanddisadvantagesofeachoneinitsfunctionasaseatShareyourideaswithaclassmate.
HaveaSeatSkillsACFigure4.
5Acarseathasaspecificfunction.
Figure4.
4Arockcanserveasaseat.
sci7_ch04_3rd.
qxd7/15/085:15PMPage100ClassifyingStructuresWeoftenclassifystructuresbylookingattheirfunctions.
Somestructuresaremadetocontainsomething,somestructuressupportsomethingontop,andsomespanaspace.
Forexample,ifyounoticesoilrunningoutofyourschoolgardenwhenitrains,youmaydecidetobuildaretainingwalltoholdthesoilin.
Ifyouhavetroublereachingahighshelf,youmayuseasteporstooltoliftyourselfup.
Ifworkersarebuildingawall,theybuildscaffoldingfirst,andwalkaroundsafely(Figure4.
6).
Abridgeisastructuredesignedtospanagap.
Sometimesthegapisastreamorriver(Figures4.
7and4.
8).
Otherbridgesspananotherroadway;ifso,wecallthebridgeanoverpass.
Earlybridgesconsistedofalogfelledoverastream;modernbridgesaredesignedinmanydifferentforms.
Lookatthebridgesinyourcommunity.
Nomatterhowsimpleorcomplicatedtheformofeachbridge,itsfunctionisstilltospanagapsafely.
Anotherwaytosortstructuresistoexaminehowtheyarebuiltandwhattheyarebuiltfrom.
WewilllookatthisinChapter5.
Athirdwaytoclassifystructuresistodividethembytheirforms,intosolidstructures,framestructures,andshellstructures.
101Designersconsidertheformandthefunctionofastructureandtheforcesthatactonit.
Figure4.
6Constructionworkerserectascaffoldsothattheycanworkonhighwalls.
Figure4.
8Coveredbridgesweredesignedandbuiltmanyyearsago.
Theroofallowedthesnowtoslideoffsothatitsweightwouldnotdamagethebridge.
ThiscoveredbridgeinGuelphwasbuiltrecentlybyvolunteers.
Figure4.
7ThreebridgesinVancouver.
ThemodernbridgeinfrontistheSkyTrainBridge,themiddleoneisaroadbridge,andthelowestisarailwaybridge.
Therailwaybridgehasa"swing"sectionthatopenstoletshipsthrough.
B5DuringReadingGoodreadersactivatetheirpriorknowledgebymakingconnectionsbetweenwhattheyreadandthemselves,theworld,and/orothertexts.
Asyoureadaboutclassifyingstructuresinthissection,thinkaboutconnectionsyoucanmaketotheinformationpresented.
MakingConnectionssci7_ch04_3rd.
qxd7/15/085:15PMPage101SolidStructuresDoyouknowwhatmountains,dams,sandcastles,waxcandles,andappleshaveincommonAllareconsideredsolidstructures(Figure4.
9).
Mostsolidstructuresaresolidallthewaythrough,althoughamountainmightcontaincaves,adammighthaveroomstoholdelectricalgenerators,andanapplemayhaveawormhole.
Asolidstructureweighsmorethanahollowstructureofthesamesizeandmadeofthesamematerial.
102UNITBStructures:FormandFunctionB6LearningCheckpointDrawatablewithfourcolumnsandsixrows.
Inthefirstcolumn,writethenamesofsixstructuresyoucanseeinyourclassroom.
Asyouworkthroughthechapter,writethefunctionofeachstructureinColumn2.
Ifyouareunsureofthefunction,putaquestionmark.
InColumn3,listthematerialseachismadeof.
InColumn4,writewhetheryouthinkitisasolidstructure,aframestructure,orashellstructure.
Compareyourtablewiththatofaclassmate.
Discusstheitemsyouputquestionmarksbeside.
Compileaclasslistfordiscussion.
WhattypesofstructurescomeupthemostoftenClassifyingStructuresFigure4.
9Packingthematerialtogetherisimportantwhenconstructingsolidstructures.
SuggestedActivityB7QuickLabonpage105FrameStructuresFramestructuresaremadeofpartsfastenedtogether.
Thepartsareoftencalledstructuralcomponents.
Forexample,yourskeletonisaframestructure.
Itsstructuralcomponents—yourbones,ligaments,andtendons—arejoinedtogether.
Abicycleframeisanotherexampleofaframestructure(seeFigure4.
10).
sci7_ch04_3rd.
qxd7/15/085:15PMPage102Framestructurescanexistasjusttheframeorasaframecoveredbyacoating.
Forexample,atennisracket,dish-dryingrack,andspider'swebarestructuresthatareonlyframes.
Umbrellas,cars,andbats'wingsconsistofaframecoveredbysomesortofmaterial.
103Designersconsidertheformandthefunctionofastructureandtheforcesthatactonit.
Figure4.
11Theigloo,theeggcarton,andtheeggshellsthemselvesareshellstructures.
SomeveryfamousstructuresfromaroundtheworldincludetheEiffelTower,theGreatWallofChina,andMountEverest.
Canyouthinkofafamoussolidstructure,shellstructure,andframestructureBeginyoursearchatScienceSource.
TakeItFurtherShellStructuresMoststrong,hollowstructuresareshellstructures.
HaveyoueverbeeninsideaniglooorlookedupintoadomedroofHaveyoupouredmilkoutofacartonintoaglassorblownupaballoonIfso,youhaveseenashellstructure(Figure4.
11).
Sinceshellstructureshavespaceinsidethem,theyoftenmakegoodcontainers.
Theyalsouseverylittlematerialintheirconstruction.
Thismeansthattheyarequitelightfortheirsize.
Clothingcanevenbeconsideredshellstructures.
Figure4.
10Adelicatespider'swebandasturdycarframearebothframestructuresbecausetheyarebuiltlikeaskeleton.
sci7_ch04_3rd.
qxd7/15/085:15PMPage103CombinationStructuresManystructuresarecombinationstructuresbecausetheyarecombinationsofshell,frame,andsolidstructures.
Forexample,Figure4.
12showshowahouseisbuiltfromsolidstructures—bricks,nails,andpiecesofwoodcalledboards.
Theboardsarenailedtogetherintoaframethatgivesthebuildingstrength.
Strengthistheabilityofanobjecttowithstandforces.
Boththewallsandtheroofarenowframestructures.
Whentheframeisfinished,thewallandroofframesarecoveredwithplywood.
Windowsanddoorsareplacedintoholescutintheplywood.
Thebuildernowcoverstheoutsidewallwithbricksorsiding,andtheroofwithshingles.
Thesekeepthehousedrywhenitrains.
104UNITBStructures:FormandFunctionFigure4.
12Ahouseisbuiltfromsolidstructuresthatareputtogethertoformaframe.
Thewallsandtheroofformacoveringaroundtheframe.
sci7_ch04_3rd.
qxd7/15/085:15PMPage104B7QuickLab105Designersconsidertheformandthefunctionofastructureandtheforcesthatactonit.
Structuresthathavethesamefunctionmayhaveverydifferentforms.
Forexample,everychairisdesignedtosupporttheweightofapersonsittingonit(Figures4.
13,4.
14,and4.
15).
Inthislab,youwillbuilddifferentformsofchairsandtesttheirstrength.
PurposeTobuildstructurestoillustratesolid,frame,andshellstructuresProcedure1.
Sketchthreechairs:onethatcanbeclassifiedasasolidstructure,oneasaframestructure,andoneasashellstructure.
2.
Buildamodelofeachchairwithtoothpicksandmodellingclay.
Trytobuildthechairsapproximatelythesamesize.
3.
Thinkofadifferentstructureandrepeatsteps1and2forthestructureofyourchoice.
4.
Asaclass,designawaytotesttheabilityofeachchairtosupportweight.
Questions5.
Whatdidyounoticeabouttheuseofmaterialswhenyoubuiltsolidstructures,framestructures,andshellstructures6.
Whichtypeofstructurewasbestabletosupportweight7.
Whatgeneralizationscanyoumakeaboutsolid,frame,andshellstructuresBuildingSolid,Frame,andShellStructuresFigure4.
13Figure4.
14Figure4.
15Materials&Equipmenttoothpicksmodellingclaysci7_ch04_3rd.
qxd7/15/085:15PMPage105106UNITBStructures:FormandFunctionB8QuickLabUnpackingthePackagingPackagingisastructurethatyouencountereveryday.
Itisusedtoprotectotherstructuresduringtransport.
Packagingalsodisplaystheproductinthestore.
Somethingassimpleasabarofsoap(asolidstructure)maycomeinacardboardbox(shellstructure)thatmightbewrappedinplastic(anothershellstructure).
Inthisactivity,youwillstudypackagingasstructures.
Whenchoosingyourpackaging,selectawidevarietyofproducts,suchasfood,schoolsupplies,andelectronics.
PurposeTostudythestructuresinvolvedinpackagingProcedure1.
Youwilllookatallofthepackagingthatcamewithseveraldifferentproducts.
Keepthesetsofpackagingseparate.
2.
Takeonesetofpackaging.
WhatdiditcontainExaminethepackagingmaterial.
Describethepackagingqualitatively,inachartliketheoneinTable4.
1.
Aqualitativedescriptionisadescriptionjustinwords(e.
g.
,describingthecolour,thetexture,theshape).
3.
Describetheamountofpackagingquantitativelybyweighingitorfindingitsvolume.
Aquantitativedescriptionisonethatusesmeasurementstodescribesomething(e.
g.
,length,weight).
Table4.
1UnpackingthePackagingRecordingChart4.
Repeattheprocessforthreemoredifferentitems.
Questions5.
Compareyourchartwiththoseofyourclassmates.
Doyouagreewiththewayyourclassmatesdescribedthevariouspackages6.
WhatstructurescamewiththemostpackagingWhatstructurescamewiththeleastWhatstructuresdoyoubuythathavenopackaging7.
Comparetheweightorvolumeofeachstructurewiththeweightorvolumeofthepackagingitcamein.
Doyounoticeanytrends8.
Doyouthinkthepackagingdiditsjob9.
DoyouthinkeachpieceofpackagingwasnecessaryMaterials&EquipmentallofthepackagingassociatedwithseveralrecentpurchasespencilandpaperkitchenorbathroomscaleQualitativeAmountofType(s)ofProductDescriptionMaterialMaterialsci7_ch04_3rd.
qxd7/15/085:15PMPage106107Designersconsidertheformandthefunctionofastructureandtheforcesthatactonit.
WhattoDo1.
Thinkaboutapackedlunchandthestructuresusedtoholdeachitem.
WhattypesofstructurearetheyConsiderThisWithaclassmateorasawholeclass,discussthefollowingquestions.
2.
Arestructuresusedtoholdfoodusuallyshellstructures,framestructures,orsolidstructuresWhydoyouthinkthatis3.
WhatmaterialsarethestructuresthatholdyourlunchmadefromCantheybereusedoraretheydisposable4.
Howmightthechoicesofstructuresweusetoholdfoodaffecttheenvironment5.
Whichismoreofachallengetotransport:solidfoodorliquidfoodWhyStructuresinYourLunchboxKeyConceptReview1.
Define"structure"inyourownwords.
Describethreewaysinwhichyoucanclassifystructures.
2.
Classifythefollowingstructuresasasolidstructure,aframestructure,orashellstructure.
(a)athree-ringbinder(d)abasketballnet(b)atent(e)aniceskate(c)abackpack(f)asandcastleConnectYourUnderstanding3.
Makeachartwithfourcolumns.
Inthefirstcolumn,listfivestructuresusedineitherasoccerorabasketballgame.
(a)InColumn2,classifyeachstructureassolid,frame,orshell.
(b)InColumn3,describetheformofeachstructure.
(c)InColumn4,statethefunctionofeachstructure.
4.
Sometimestransportingstructuresexposesthemtoforcesthattheywouldnotencounterduringnormaluse.
(a)Listdifferentwaysthatyouhaveseenstructuresprotectedforshipping.
(b)Describeonewaythatyoufeeliseffective.
(c)Describeonewaythatyoufeelisnot.
(d)Whatdoyoudowithpackagingmaterialsafteryouunpackastructure5.
DoyouthinkadesignershouldbeginworkwithforminmindorwithfunctioninmindGivereasonsforyourthinking.
PractiseYourSkills6.
Thinkofastructurethatcanbeclassifiedasbothaframestructureandashellstructure.
Drawasimplediagramtohelpyouexplainwhythestructurecanbeclassifiedinbothways.
Formorequestions,gotoScienceSource.
4.
1CHECKandREFLECTSTSEB9ThinkingaboutScienceandTechnologysci7_ch04_3rd.
qxd7/15/085:15PMPage107