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1、__________________________________________________MeasurementBasequantitiesandtheirunits;mass(kg),length(m),time(s),current(A),temperature(K),amountofsubstance(mol):Derivedunitsasproductsorquotientsofthebaseunits:收集于网络，如有侵权请联系管理员删除_______________________
2、___________________________Prefixesandtheirsymbolstoindicatedecimalsub-multiplesormultiplesofbothbaseandderivedunits:Estimatesofphysicalquantities:Whenmakinganestimate,itisonlyreasonabletogivethefigureto1oratmost2significantfiguressinceanestimateisnotver
3、yprecise.·Occasionally,studentsareaskedtoestimatetheareaunderagraph.Theusualmethodofcountingsquareswithintheenclosedareaisused.(eg.Topic3(Dynamics),N94P2Q1c)·Often,whenmakinganestimate,aformulaandasimplecalculationmaybeinvolved.EXAMPLE1:Estimatetheaverag
4、erunningspeedofatypical17-year-old‟s2.4-kmrun.velocity=distance/time=2400/(12.5x60)=3.2≈3ms-1收集于网络，如有侵权请联系管理员删除__________________________________________________EXAMPLE2:Whichestimateisrealistic?Distinctionbetweensystematicerrors(includingzeroerrors)andr
5、andomerrorsandbetweenprecisionandaccuracy:Randomerror:isthetypeoferrorwhichcausesreadingstoscatteraboutthetruevalue.Systematicerror:isthetypeoferrorwhichcausesreadingstodeviateinonedirectionfromthetruevalue.Precision:referstothedegreeofagreement(scatter,
6、spread)ofrepeatedmeasurementsofthesamequantity.{NB:regardlessofwhetherornottheyarecorrect.}Accuracy:referstothedegreeofagreementbetweentheresultofameasurementandthetruevalueofthequantity.收集于网络，如有侵权请联系管理员删除_________________________________________________
7、_Assesstheuncertaintyinaderivedquantitybysimpleadditionofactual,fractionalorpercentageuncertainties(arigorousstatisticaltreatmentisnotrequired).Foraquantityx=(2.0±0.1)mm,Actual/Absoluteuncertainty,Δx=±0.1mmFractionaluncertainty,Δxx=0.05100%=5%´Percentage
8、uncertainty,ΔxxIfp=(2x+y)/3orp=(2x-y)/3,Δp=(2Δx+Δy)/3Ifr=2xy3orr=2x/y3,Δr/r=Δx/x+3Δy/yActualerrormustberecordedtoonly1significantfigure,&
Thenumberofdecimalplacesacalculatedquantityshouldhaveisdeterminedbyitsactualerror.Fo
