Sec 2 G3 Chapter 9- application of forces and transfer of energy

CHAPTER9: ApplicationofforcesandtransferofenergyTYPESOfFORCES: 2.Non-contactforces-forcesexperiencedbybodieseveniftheyarenotinphysical1. Contactforces- forcesexperiencedbybodieswhentheyareinphysicalI /I contactwithcontactFrictional Tgravitationalmagneticelectrostatic eachotherapplied It↓ ~ forceface Forceexertedforceexertedforceofattractionbetweentwomassesbyachargebbyamagnetbodyonanotheri.e.thatattractsforcedueforcesactingopposite chargedbodyobjectstoEarthtotheaction ofMusclestothedirectionofmotion 3. friction- thecontactforcethatopposes/tendstoopposemotionbetweensurfacesincontact specialcases: 1. wheels 2,feetwalking*Notionofwheel *motionofobject *directionoffriction *directionoffriction1hM -> · tomovetotheright,thewheelshastorotateinaclockwisedirection· tomovetoright,thefoothastopushbackwardstotheground · frictionopposesmotion,thereforeitactstotheright ·frictionopposesmotion,thereforeitactstotheright Reducingnegativeeffectsoffriction wheels ballbearings directionof sphericalballbearingsworklikewheels.Theyrollaround,insteadofdraggingtheboxovertheground,motion thecircularshapeofthewheelsrotateandpreventsᶏ·allbearingsapevenmoving surfacesinmachinesfromrubbingagainst t beesdirectcontactwiththeground.Withlessfriction,one smallerforceisneededtomoveashoppingtrolley lubricant aircushion withlubricantadded,enginesurfacesincontactexperiencelessfrictionwhentheymoveagainstalayerofairbetweensurfacesreducesfriction,soahovercraftcantravelfaster eachother.Aroughsurfacegeneratesmorefrictioncomparedtothesmoothsurface Enhancingpositiveeffectsoffriction Treads->channelwateroutfromundertyres,whichimprovesthetyresgripontheroadsurface,andpreventsvehiclesfromskidding Farachute->thelargeairresistancecreatedbythecanopyofanopenparachuteslowsdownadescendingparachutist,sothathemaylandsafely Chalk->rockclimbersapplychalkpowdertotheirpalmstoabsorbsweet,andhenceimprovetheirgrip Comparingweightandmass weight Mass definition:themeasureofthegravitationalforceactingonanobject amountofmatterinanobject changes: canhavedifferentvaluesdependingongravitationalfieldstrength valueremainsunchanged,independentofgravitationalfieldstrength

SIunit: Newton(N) Kilogram(kg)instrumentto measure: springbalance electronicmassbalancebeambalance formulato(N)(kg)(n/kg) w (kg)(N)(N/kg)calculate: weight=massXgravitationalfieldstrength m9 mass=weight:gravitationalfieldstrength Gravitationalfield gravitationalfieldisaregioninwhichamassexperiencesagravitationalforceofattraction gravitationalfieldstrength,g,isthegravitationalforceactingperunitmass gravitationalfieldgetsstrongerastheobjectmovesclosertoearth onearth onMoon gravitationalfieldstrength,g:CON/kg 1.56N/kg -anobjectwithaMassof1kgwould ->anobjectwithamassoflkgwouldbe beattractedtowardsthecentreoftheearth attractedtowardsthecentreoftheEarthbya byaforceofION forceof1.66N TheforceofgravityontheMoonislessthanonEarth. AnyobjectwillweighlessonMoonthanonEarth.However,theobjectwouldhavethesamemassonMoon andEarth Whathappenswhentwoormoreobjectsinteract? fo