H2 Physics Explanations

1 H2PhysicsExplanations Syllabusdocumenthttps://www.seab.gov.sg/docs/default-source/national-examinations/syllabus/alevel/2024syllabus/9749_y24_sy.pdf Measurement● Explainwhy…helpsimprovereliabilityReliabilityislinkedtopercentageuncertaintyMarks:- Givedefinition/formula:%uncertainty=absoluteuncertainty/datavalue(givengraph,thebestdatapointwouldbetheonewiththelargestdatavalue)- Largerdatavaluereduced%uncertainty ● Explainwhichquantityhasthegreatestcontributiontotheuncertaintyofsomevariable.Seeexpressionofvariable.“Quantityisraisedtothepowerofxxx,soitcontributesgreatesttotheuncertaintyofthevariable.” ● Howdoestakingmanyreadingsandtakingaveragehelptoreducerandomerror?- Absoluteuncertaintyisthesame- Percentageuncertaintyiscalculatedbydividingabsoluteuncertaintyoveralargermeasurement- %uncertaintyisreduced ● Sometimesqnaskutosuggestanothermethodtoincreaseaccuracyofmeasurement.Theyactuallymeanaccuracyasprecision:< Kinematics● Accelerationchangedfrom+to-inthesameinstant.Whyisthisnotpossible?2accelerationsinthesameinstant->2netforces->impossible ● Explainhowthepathtakenbytheparticlecanbeconsideredparabolic.Parabolicmotionconditions:1. Constantacceleration(likeinkinematics)a. Provethattheresultantforcehasconstantmagnitudeanddirection.Egweightandelectricforcehaveconstantmagnitudeanddirection,sothenetforcehasconstantmaganddir.2. Onecomponentofvelocityisindirofacceleration,oneperpendicularcomponentofvelocityhasnoacceleration. Forces● Previouscalculationsshowthattheobjectisnotinrotationalequilibrium.However, wheninuse,theobjectisinequilibrium.Explainwhy.Think:whatwasn'tconsideredinpreviouscalculations?Eg(weightofjib,counterjib,massesatbottom)

2 Thesecausemomentsaboutpivot→helpcauseobjecttobeinequilibrium ● Whataretheoriginsofupthrust 1. Upthrustoriginatesfromthepressuredifferencebetweentopandbottomofthebody.2. (whyistherepressuredifference)Aspressureincreaseswithincreasingdepth,bottomisatlargerdepth,soupwardforceonbottomishigherthandownwardforceontop3. Linkpressuretoforce:Upthrustisproductofpressuredifferenceandcrosssectionalarea. ● Showupthrust=value.Explainyourworking.Upthrust=weightoffluiddisplaced ● Giventhatthereare3forces,1stforceisvertical,2ndforcehasbothverticalandhorizontalcomponents,explainwhythe3rdforcecannotbeverticaliftheobjectisinequilibrium.2ndforcehase.g.leftwardshorizontalcomponentofforce.Fortheobjecttobeinequilibrium,netforce=0N.Hencethe3rdforceneedstohavearightwardshorizontalcomponent. Alternatively,sayvectorsummustbe0.Thendrawthetriangle. ● Whysmallobjectsincircularmotioncanbedangerousforsatellites “Dangerousforsatellites”<-collision<-force<-N2L<-momentum<-p=mv<-highvelocity ● Whyisspeedofmoleculevibrationlowerthanspeedofsoundingasspeedofsoundingasisspeedofenergytransferwhilespeedifvibrationisspeedofoscillation ● Originofenergytransferinsoundwaves?mechanicalenergyofvibratingobject ● Originofrestoringforceonamoleculeasitvibrates?Gashasweight,andcanexertpressure.Pressuredifferenceexertsrestoringforce. ● Originofforcethatacceleratestrolley,u