大学物理演示实验-英文版VIP免费

BuildaRaftPoweredbySurfaceTensionAbstractHaveyoueverwonderedwhyawaterstridercanwalkonwater?Orhowdetergentcancleanyourdishes?Ifyouobservecarefully,youcanfinddozensofsimilarlyinterestingphenomenathatarealllinkedtothesurfacetensionofwater.Thisscienceprojectwillhelpyouunderstandandmeasurethepropertiesofwatersurfacetension.ObjectiveInthisscienceproject,youwill:1.Developanunderstandingofwatersurfacetension,2.Understandchangesinwatersurfacetensionundervariousconditions,3.Makemeasurementstoestimatethenetwatersurfacetension.IntroductionIfyou'veeverblownupaballoon,youknowit'sprettyeasytoblowupwithoutbecomingoutofbreathwhenit'smadeofsoft,stretchyrubber.That'sbecausetheballoonofferslittleresistancetobecomingstretchedoutasitisblownup.Butforaballoonmadeofthickerorstifferrubber,moreenergyisrequiredtoblowitup.Theballoonoffersmoreresistancetostretching.Thinkofaballoonasamodelforsurfacetension.How"stretchy"theballoonmaterialisdetermineshowmuchresistance(surfacetension)mustbeovercomebytheenergyofyourblowinginordertoinflatetheballoon.Surfacetensionisdefinedastheenergyrequiredtoincreasethesurfaceareabyaunitamount.Liquidsalsoexperiencesurfacetension.Themolecules(smallindividualparticles)oftheliquidexperienceintermolecularattractions,whichsimplymeansthemoleculesarepullingandpushingawayfromeachother,justlikemagnetsbothattractandrepeleachother.Inthecaseofawatermoleculesurroundedonallsidesbyotherwatermolecules,everypullingforceisbalancedbyapushingforce.Thenet(whichmeansoverall)effectisnochange.Butatthesurface,whereairandwatermeet,thatisn'ttrue.Thewatermoleculesatthesurfaceexperiencemorepullsdownwardtowardtheotherwatermoleculesbelowthemthanupwardtowardtheair.Thisisthesurfacetensionofthewater.Youcanseeitatworkwhenyoufillaglass.Evenifthewaterisattherimoftheglass,youcanaddjustafewmoredropssothatthewaterisslightlytallerthantherim.Don'tbelieveit?Lookatthepicturebelowandthentryityourself!Figure1.Becauseofsurfacetension,thetopofthisfullglassofwatercurvesoutward.Ifmorewaterisadded,itwilleventuallyspilloverthesideoftheglass.Notetheedgeoftheglass,andhowfarthewatercurvesoverit.Inthisscienceproject,you'llmakeasmallraftfromaclearplasticsheet(atransparency),andseeifyoucanpropelitbytakingadvantageofthesurfacetensionofwater.Terms,Concepts,andQuestionstoStartBackgroundResearchResistanceSurfacetensionMoleculeVelocityKineticenergyMassAccelerationBibliographyThesewebsitesaregoodintroductionstosurfacetension:MassachusettsInstituteofTechnology.(n.d.).IntroductiontoSurfaceTension.RetrievedAugust12,2010,fromhttp://web.mit.edu/nnf/education/wettability/intro.htmlExploratorium.(n.d.).StickyWater.RetrievedAugust12,2010,fromhttp://www.exploratorium.edu/ronh/bubbles/sticky_water.htmlThiswebsiteoffersanexplanationofvelocity:Physics4Kids.(n.d.).Velocity,Speed,andMotion...OhMy!RetrievedAugust12,2010,fromhttp://www.physics4kids.com/files/motion_velocity.htmlThiswebsiteexplainskineticenergy:Zobel,E.A.(n.d.).KineticEnergy.RetrievedAugust12,2010,fromhttp://zonalandeducation.com/mstm/physics/mechanics/energy/kineticEnergy/kineticEnergy.htmlMaterialsandEquipmentTransparencies,likethoseusedonanoverheadprojector(1box);availableatyourlocalofficesupplystoreMarkerRuler,metricScissorsKitchensponges(1package)TapeLabnotebookLiquidlaundrydetergentEyedropper;availableatyourlocalpharmacyStopwatch,accura...