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38
ChapterII
Intheconclusionofhispapershesays:uTheaimhasbeenonlyto
showthatAristotlediddeliberatelyformulatemathematicalulaws”of
physicswhichwerebasedfrmlyonobservedfacts.”3
AristotledevotesmainlytwoBooksofhisPhysicstotheproblemof
localmotion,namelyBookIVandVII.InthefnalpartofBookVII
heprovidesuswiththefamousulawsofmotion”relatingthefactorsof
motionasfollows:
If,then,AthemoventhavemovedBadistanceCinatimeD,
theninthesametimethesameforceAwillmove½Btwicethe
distanceC,andin½Ditwillmove½BthewholedistanceC:
forthustherulesofproportionwillbeobserved.Again,ifagiven
forcemovesagivenweightacertaindistanceinacertaintimeand
halfthedistanceinhalfthetime,halfthemotivepowerwillmove
halftheweightthesamedistanceinthesametime.LetErepresent
halfthemotivepowerAandFhalftheweightB:thentheratio
betweenthemotivepowerandtheweightintheonecaseissimilar
andproportionatetotheratiointheother,sothateachforcewill
causethesamedistancetobetraversedinthesametime.4
Atfrstglance,theselawsdescribingtherelationshipbetweenthe
factorscausingmotion,i.e.,itscausesofmotion(actingforceandresis-
tance)anddistancetraversedandtimeconsumedinitseffects(speed)
seemtobecorrect.Observationanducommonsense”convinceusthat
ifanactingforceAcanmovesomeweightBtodistanceC,thesame
forceatthesametimewillmovehalfoftheweightBtotwicethedis-
tanceC,ortothesamedistance,butintwiceshortertime.Inbothcases
Bwouldbemovedtwiceasfast.Similarly,theforcethatishalftheforce
AwillmovehalftheweightBforthesamedistanceCinthesametime,
sincetheratioofforcetoweightisthesameinthiscase.However,
afurtherstatementshowsthattherelationshipsbetweenthesefactors
aremorecomplicatedbecause,asAristotlesays:
ulawsofproportionality”seee.g.,A.Gregory,Aristotle,DynamicsandProportional-
ity,uEarlyScienceandMedicine”61(2001),pp.1-20.
3E.Hussey,Aristotle)sMathematicalPhysics,p.242.
4Aristotle,Physics,250a,2-9,BkVII,R.P.Hardie,R.K.Gaye(transl.),[in:]uThe
BasicWorksofAristotle”,R.McKeaon(ed.),NewYork2001,p.353.