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7.6PreModernPeriod, Seventeenth Century 145

appointedGreshamProfessorof Geometryat Oxfordin 1665.AftertheGreatFireof London

in 1666,hewas appointedsurveyor of London,andhedesignedmany buildings.

57 Hooke anticipatedsomeof themostimportant discoveriesandinventionsof histimebutfailed

to carrymany of themthroughto completion. Heformulatedthetheoryof planetarymotion

as a problemin mechanics,andgrasped,butdidnotdevelopmathematically, thefundamental

theoryonwhich Newtonformulatedthelaw of gravitation.

58 Hismostimportant contributionwas publishedin 1678in thepaperDePotentiaRestitutiva.

It containedresultsof hisexperiments withelasticbodies,andwas therstpaper in which the

elasticpropertiesof materialwas discused,Fig.7.12.

Figure7.12: ExperimentalSetUpUsedby Hooke

\Takea wire stringof 20,or 30,or 40 ft long,andfastentheupper partthereof to

a nail,andto theotherendfastena Scaleto receivetheweights:Thenwitha pair

of compassestakethedistance of thebottomof thescalefromthegroundor
oor

underneath,andsetdownthesaiddistance,thenputinweightsintothesaidscale

andmeasure theseveral stretchingsof thesaidstring, andsetthemdown. Then

compare theseveral strtchingsof thesaidstring, andyouwill ndthattheywill

alwaysbear thesameproportionsoneto theotherthattheweightsdothatmade

them".

ThisbecameHooke'sLaw=E".

59 Becausehewas concernedaboutpatent rights to hisinvention,hedidnotpublishhislaw

whenrstdiscoveredit in 1660.Insteadhe publishedit in theformof ananagram\ceiinossst-

tuu" in 1676andthesolutionwas given in 1678.Ut tensiosicvis(atthetimethetwo symbos

uandvwereemployedinterchangeablyto denoteeitherthevoweluor theconsonantv), i.e.

extensionvariesdirectlywithforce.

7.6.2 Newton,1642-1727

60 Bornonchristmasday in theyearof Galileo'sdeath,Newton,Fig. 7.13was Professorof