force physics force interaction unopposed change motion object words force cause object mass change velocity includes begin moving state rest accelerate force described intuitive concepts push pull force magnitude direction making quantity measured unit represented symbol original form newton second law states net force acting object equal rate momentum changes time mass object constant law implies acceleration object directly proportional net force acting object direction net force proportional mass object related concepts force include thrust increases velocity object drag decreases velocity object produces changes speed object extended body usually applies forces adjacent parts distribution forces body called mechanical stress pressure simple type stress stress usually causes solid materials flow development concept philosophers antiquity concept force study stationary moving objects simple machines aristotle retained fundamental errors understanding force incomplete understanding non obvious force friction consequently inadequate view nature natural motion fundamental error belief force required maintain motion constant velocity previous motion force eventually corrected sir mathematical insight sir formulated laws motion improved nearly years early 20th century developed theory correctly predicted action forces objects increasing near speed light provided insight forces produced modern insights quantum mechanics technology accelerate particles close speed light particle physics devised standard model describe forces particles smaller standard model exchanged particles called gauge fundamental means forces emitted absorbed main interactions known order decreasing strength strong electromagnetic weak high energy particle physics observations 1970s 1980s confirmed weak electromagnetic forces expressions fundamental interaction pre concepts antiquity concept force recognized integral functioning simple machines mechanical advantage given simple machine allowed force exchange force acting greater distance work analysis characteristics forces ultimately culminated work especially famous treatment forces inherent aristotle provided philosophical discussion concept force integral aristotle view terrestrial sphere contained elements come rest different natural places aristotle believed objects earth composed elements earth water natural place ground stay way left distinguished innate tendency objects find natural place heavy bodies fall led natural motion unnatural forced motion required continued application force theory based everyday experience objects constant application force needed cart moving conceptual trouble accounting behavior projectiles flight arrows place archer moves start flight sailed air efficient cause acts aristotle aware problem proposed air displaced path carries target explanation demands like air change place general physics began facing criticism medieval science 6th century shortcomings physics fully corrected 17th century work influenced late medieval idea objects forced motion carried innate force impetus constructed experiment stones rolled theory motion early 17th century showed bodies accelerated gravity extent independent mass argued objects retain velocity acted force example friction mechanics sir sought describe motion objects concepts force found obey certain conservation laws newton went publish thesis work newton set laws motion day way forces described physics law newton law motion states objects continue state constant velocity acted external net force resultant force law extension insight constant velocity associated lack net force detailed description newton proposed object mass innate functions fundamental natural state place idea natural state rest law intuitive belief net force required object moving constant velocity making rest physically indistinguishable non zero constant velocity newton law directly connects concept relative specifically systems objects moving different impossible determine object motion object rest words phrase matters technically laws physics frame reference frames related transformation instance traveling moving vehicle constant velocity laws physics change rest person throw ball straight air catch falls worrying applying force direction vehicle moving true person observing moving vehicle pass observes ball follow curving path direction motion vehicle ball associated constant velocity direction vehicle motion ensures ball continues forward thrown falls perspective person car vehicle inside rest outside world moving constant speed opposite direction experiment distinguish vehicle rest outside world rest situations considered physically indistinguishable applies equally constant velocity motion rest concept explain tendency objects continue different forms constant motion strictly constant velocity planet earth length day length year extended principle explained reference frames subject constant acceleration free falling object physically equivalent reference frames example experience free fall orbit earth newton laws motion easily environments astronaut places object mass mid air remain stationary respect astronaut thing occur astronaut object space net force gravity acting shared reference frame principle development general theory second law modern statement newton second law equation formula formula momentum system formula net sum force zero net force definition balanced forces present contrast second law states force acting object result object momentum changing time definition momentum formula mass formula velocity newton second law applies system constant mass moved outside derivative operator equation formula definition acceleration version newton second law derived formula newton explicitly stated formula reduced form newton second law asserts direct acceleration force acceleration mass defined measurements described reference frame analysis advanced physics deep questions remain proper definition mass general offers space time mass lacking coherent theory quantum gravity unclear connection relevant justification newton second law taken definition mass writing law equality relative units force mass fixed use newton second law definition force rigorous textbooks essentially mathematical notable philosophers sought explicit definition concept force include newton second law measure strength forces instance knowledge masses planets allows scientists forces planets law newton law result applying symmetry situations forces attributed presence different objects law means forces interactions different bodies thing force force acts body body force second body second body force body equal magnitude opposite direction law referred action reaction law called action reaction action reaction simultaneous formula object object considered system net force system interactions objects zero formula formula means closed system particles internal forces action reaction force shared objects closed system cause center mass system accelerate constituent objects accelerate respect system remains alternatively external force acts system center mass experience acceleration proportional magnitude external force divided mass system combining newton second laws possible linear momentum system formula integrating respect time equation formula obtained system includes objects conservation linear momentum similar arguments possible system arbitrary number particles shows exchanging momentum constituent objects affect net momentum system general long forces interaction objects mass possible define system net momentum lost gained special theory special theory mass energy equivalent seen calculating work required accelerate object object velocity increases energy mass equivalent requires force accelerate lower velocity newton second law formula remains valid mathematical definition order momentum formula formula velocity formula speed light formula rest mass expression relating force acceleration particle constant non zero rest mass formula moving formula direction formula formula formula factor formula early history expressions formula formula called longitudinal transverse mass force produce constant acceleration decreasing acceleration object approaches speed light note formula object non zero rest mass speed light theory yields prediction speed formula small compared formula formula close formula close use restore form formula use relation correct formula force formula mass formula acceleration descriptions forces perceived pushes pulls provide intuitive understanding describing forces physical concepts temperature intuitive understanding forces precise operational definitions consistent direct observations compared standard measurement scale experimentation determined laboratory measurements forces fully consistent conceptual definition force offered mechanics forces act particular direction sizes dependent strong push pull characteristics forces classified quantities means forces follow different set mathematical rules physical quantities direction denoted quantities example determining happens forces act object necessary know magnitude direction forces result pieces information known force situation ambiguous example know people pulling rope known force know direction person pulling impossible determine acceleration rope people pulling war people pulling direction simple dimensional example knowing direction forces impossible decide net force result adding force forces avoids problems historically forces investigated conditions static forces canceled experiments demonstrate crucial properties forces quantities magnitude direction forces act point particle resulting force resultant called net force determined following rule addition addition represented sides gives equivalent resultant equal magnitude direction magnitude resultant varies difference forces sum depending angle lines action forces acting extended body respective lines application specified order account effects motion body free body convenient way track forces acting system drawn angles relative force preserved graphical addition determine net force added forces resolved independent components right angles horizontal force pointing northeast split forces pointing north pointing east component forces addition yields original force resolving force components set basis clean way describe forces directions components components sum uniquely determined addition components individual components independent forces acting ninety degrees effect magnitude direction choosing set basis considering set basis mathematics convenient choosing basis direction forces desirable force non zero component force dimensional component right angles occurs resultant force acting point particle zero sum forces zero dealing extended body necessary net kinds static dynamic static static understood invention classical mechanics objects rest zero net force acting simplest case static occurs forces equal magnitude opposite direction example object level surface pulled attracted downward center earth force gravity time surface forces resist downward force equal upward force called normal force situation zero net force acceleration pushing object surface result situation object applied force opposed static friction generated object table surface situation movement static friction force exactly applied force resulting acceleration static friction increases decreases response applied force upper limit determined characteristics contact surface object static forces usual way measuring forces simple devices weighing scales spring example object suspended vertical spring scale experiences force gravity acting object balanced force applied spring reaction force equals object weight tools force laws discovered force gravity proportional volume objects constant density widely exploited define standard weights principle analysis law gas pressure law springs formulated verified laws motion dynamic dynamic described noticed certain assumptions physics contradicted observations logic realized simple velocity addition demands concept absolute rest frame exist concluded motion constant velocity completely equivalent rest contrary aristotle notion natural state rest objects mass naturally approached simple experiments showed understanding constant velocity rest correct example dropped crow nest ship moving constant velocity physics fall straight ship moved beneath universe falling land foot mast moving ship experiment actually conducted falls foot mast knows travel ship despite separated forward horizontal force applied falls conclusion left continues velocity boat falls force required moving constant forward velocity object traveling constant velocity subject zero net force resultant force definition dynamic forces object balance moves constant velocity simple case dynamic occurs constant velocity motion surface friction situation force applied direction motion friction force exactly opposes applied force results zero net force object started non zero velocity continues non zero velocity aristotle motion caused applied force friction taken consideration clear net force causing constant velocity motion forces notion force keeps meaning quantum mechanics dealing operators instead classical physics described equation instead consequence results measurement appear portions course difficult imagine context forces fields forces generally derived treated similar classical position formula different framework quantum field theory fields quantum mechanics particles acting possess spatial variable angular momentum like variable called spin principle relating space spin depending value spin identical particles split different classes identical spin function parallel spins spatial exclude places force vice versa spins position apparent force attractive case strictly negative spatial spin electromagnetic waves strictly positive notion force loses meaning modern particle physics forces acceleration particles explained mathematical product exchange momentum carrying gauge development quantum field theory general realized force redundant concept arising conservation momentum momentum momentum virtual particles quantum conservation momentum directly derived symmetry space usually considered fundamental concept force currently known fundamental forces considered accurately fundamental interactions particle creates virtual particle momentum conservation results particle making impression attraction particles exchanging description applies forces arising fundamental interactions sophisticated mathematical descriptions needed predict detail accurate result interactions simple way describe interactions use matter particle represented straight line world line traveling time normally increases right matter anti matter particles identical direction propagation world lines particles intersect interaction represents force arising interaction occurring associated change direction particle world lines gauge emitted away lines case virtual particle exchange absorbed adjacent utility types physical phenomena general picture fundamental interactions separate forces described rules example describe detail electron interaction gauge responsible weak nuclear force fundamental forces forces universe based fundamental interactions strong weak forces nuclear forces act short distances responsible interactions particles including compound electromagnetic force acts electric charges force acts masses forces nature derive fundamental interactions example friction manifestation electromagnetic force acting surfaces exclusion principle permit pass similarly forces springs modeled law result electromagnetic forces exclusion principle acting return object position forces acceleration forces arise simply acceleration rotating frames reference development fundamental theories forces proceeded lines unification disparate ideas example unified force responsible objects falling surface earth force responsible mechanics universal theory demonstrated electric magnetic forces unified consistent theory 20th century development quantum mechanics led modern understanding fundamental forces gravity matter interacting exchanging virtual particles called gauge standard model particle physics similarity forces led scientists predict unification weak electromagnetic forces theory subsequently confirmed observation complete standard model mechanism observations indicate standard model incomplete grand unified theory allowing combination interaction strong force held possibility candidate theories proposed accommodate outstanding problems physics attempting develop self consistent unification models combine fundamental interactions theory tried failed endeavor currently popular approach answering question string theory gravity identified universal force work newton tendency objects fall earth understood related motions objects instrumental describing characteristics falling objects determining acceleration object free fall constant independent mass object today acceleration gravity surface earth usually designated formula magnitude meters second squared measurement taken sea level vary depending location points center earth observation means force gravity object earth surface directly proportional object mass object mass formula experience force formula free fall force unopposed net force object weight objects free fall force gravity opposed reactions supports example person standing ground experiences zero net force weight balanced normal force exerted ground newton contribution theory unify motions heavenly bodies aristotle assumed natural state constant motion falling motion observed earth proposed law gravity account motions described earlier laws motion newton came realize effects gravity observed different ways larger distances particular newton determined acceleration moon earth ascribed force gravity acceleration gravity decreased square law newton realized acceleration gravity proportional mass attracting body combining ideas gives formula relates mass formula radius formula earth acceleration formula direction given formula unit directed outward center earth equation dimensional constant formula describe relative strength gravity constant come known newton value unknown newton lifetime able measurement formula balance widely reported press measurement mass earth knowing formula allow solve earth mass given equation newton realized bodies followed laws motion law gravity universal stated newton states force spherical object mass formula pull mass formula formula formula distance objects centers mass formula unit pointed direction away center object center second object formula powerful stand basis subsequent descriptions motion solar system 20th century time sophisticated methods analysis invented influence multiple bodies planet moon exact allow predict existence planet neptune observed orbit planet mercury newton fully explain predicted existence planet vulcan explain despite early indications planet found formulated theory general turned attention problem mercury orbit found theory added correction account time newton shown correct alternative far general acknowledged theory best explains gravity viewed force objects moving freely fields travel straight lines curved space time defined shortest space time path space time events perspective object motion occurs whatsoever observing motion global sense space time observed force object curved path straight line path space time seen curved line space called trajectory object example basketball thrown ground moves uniform field space time trajectory extra dimension added straight line slightly curved radius order light years time derivative changing momentum object label force electromagnetic force described force existed charges properties force varied square law directed radial direction attractive independent mass charged objects followed principle law observations statement subsequent found construct electric field useful determining force electric charge point space electric field based hypothetical test charge space law determine force electric field space defined formula formula magnitude hypothetical test charge force discovered exist electric currents mathematical character like currents attract unlike currents repel similar electric field magnetic field determine magnetic force electric current point space case magnitude magnetic field determined formula formula magnitude hypothetical test current formula length hypothetical wire test current flows magnetic field force including example fact earth magnetic field aligned closely orientation earth axis causes compass oriented magnetic force pulling needle combining definition electric current time rate change electric charge rule called law describes force charge moving magnetic field connection electricity allows description unified electromagnetic force acts charge force written sum force electric field magnetic force magnetic field fully stated law formula formula electromagnetic force formula magnitude charge particle formula electric field formula velocity particle crossed magnetic field formula origin electric magnetic fields fully explained unified number earlier theories set later fully described sources fields stationary moving charges interactions fields led discover electric magnetic fields self generating wave traveled speed calculated speed light insight united nascent fields electromagnetic theory led directly complete description electromagnetic spectrum attempting reconcile electromagnetic theory observations effect proved troublesome work leading theoretical new theory developed quantum mechanics final modification electromagnetic theory ultimately led quantum fully describes electromagnetic phenomena wave particles known fundamental exchange particle described interactions relating including electromagnetic force common solid matter like charges influence electromagnetic force characteristics actually result exclusion principle occupy quantum mechanical state material densely packed lower energy quantum mechanical states higher energy states means takes energy pack effect manifested structural force technically result existence finite set electron states strong nuclear nuclear forces today usually described interactions place quantum theories particle physics strong nuclear force force responsible structural integrity atomic weak nuclear force responsible decay certain types strong force today understood represent interactions detailed theory quantum strong force fundamental force acting named strong interaction strongest fundamental forces strong force acts directly elementary particles force observed best known example force acts atomic nuclear force strong force acts indirectly transmitted form virtual transmit nuclear force topic failure searches free shown elementary particles affected directly phenomenon called color confinement weak nuclear weak force exchange heavy familiar effect beta decay atomic associated word weak derives fact field strength times strong force stronger gravity short distances consistent theory developed shows electromagnetic forces weak force indistinguishable temperatures excess approximately temperatures modern particle conditions universe early moments non fundamental forces forces consequences fundamental ones situations models utilized gain physical insight normal force normal force forces interaction close contact electron clouds overlap nature follows resulting force acts direction normal surface interface objects normal force example responsible structural integrity tables floors force responds external force pushes solid object example normal force action impact force object crashing surface friction friction surface force opposes relative motion force directly related normal force acts solid objects separated point contact broad classifications forces static friction friction static friction force formula exactly oppose forces applied object parallel surface contact limit specified static friction formula multiplied normal force formula words magnitude static friction force inequality formula friction force formula independent forces applied movement object magnitude force equals formula formula friction surface friction static friction tension tension forces modeled ideal strings combined ideal allow ideal strings switch physical direction ideal strings transmit tension forces action reaction pairs objects connected ideal string force directed string object accompanied force directed string opposite direction second object connecting string multiple times object use set uses tension force load multiplied string acts load factor tension force string acts load machines allow increase force corresponding increase length string displaced order load tandem effects result ultimately conservation mechanical energy work load matter complicated machine elastic force elastic force acts return spring natural length ideal spring taken infinitely springs exert forces push contracted pull extended proportion displacement spring position linear relationship described law named formula displacement force exerted ideal spring equals formula formula spring constant force constant particular spring minus sign accounts tendency force act opposition applied load mechanics newton laws mechanics general developed describe forces affect point particles dimensional objects real life matter extended structure forces act object affect parts object situations holding object able flow contract expand change shape theories mechanics describe way forces affect material example extended differences pressure result forces directed pressure follows formula formula volume object fluid formula function describes pressure locations space pressure result force suspended fields winds atmospheric science lift associated flight specific instance force associated dynamic pressure fluid resistance body force motion object fluid called drag force approximately proportional velocity opposite direction formula formula constant depends properties fluid dimensions object usually cross area formula velocity object formally forces mechanics fully described stress terms roughly defined formula formula relevant cross area volume stress calculated includes pressure terms associated forces act normal cross area matrix shear terms associated forces act parallel cross area diagonal elements stress accounts forces cause strains including stresses fictitious forces forces frame dependent meaning appear adoption non non reference frames forces include force force forces considered fictitious exist frames reference accelerating forces genuine referred pseudo forces general gravity fictitious force arises situations flat geometry extension theory string theory fundamental forces respectively differently scaled dimensions ultimately imply forces fictitious forces cause extended objects rotate associated force formula defined relative arbitrary reference point cross product formula formula position force application point relative reference point rotation equivalent force way angle equivalent position angular velocity velocity angular momentum momentum consequence newton law motion exists ensures bodies maintain angular momentum acted likewise newton second law motion derive analogous equation angular acceleration rigid body formula formula moment body formula angular acceleration body provides definition moment equivalent mass advanced treatments mechanics rotation time interval described moment substituted properly analyzed fully determines characteristics including differential form newton second law provides alternative definition formula formula angular momentum particle newton law motion requires objects experience equal opposite directly implies conservation angular momentum closed systems experience revolutions action internal force object accelerating circular motion force acting object equals formula formula mass object formula velocity object formula distance center circular path formula unit pointing radial direction center means force felt object directed center curving path forces act perpendicular velocity associated motion object change speed object magnitude velocity direction velocity force object resolved component perpendicular path path yields force object slowing speeding radial force changes direction forces define number physical concepts integrating respect example integrating respect time gives definition impulse formula newton second law equivalent change momentum yielding impulse momentum similarly integrating respect position gives definition work force formula equivalent changes energy yielding work energy power rate change work trajectory extended position change formula time interval formula formula velocity potential energy instead force related concept potential energy field convenience instance force acting object seen action field present object location definition energy definition work potential field formula defined field gradient equal opposite force produced point formula forces classified conservative conservative forces equivalent gradient potential forces conservative forces conservative force acts closed system associated mechanical work allows energy convert potential forms means closed system net mechanical energy conservative force acts system force related directly difference potential energy different locations space considered artifact potential field way direction flow water considered artifact map elevation area conservative forces include gravity electromagnetic force spring force forces models dependent position given radial formula examples follow gravity formula formula constant formula mass object forces formula formula electric free space formula electric charge object spring forces formula formula spring constant forces certain physical scenarios impossible model forces gradient considerations yield forces arising statistical average example friction caused numerous force model independent position forces friction include contact forces tension compression drag sufficiently detailed description forces results conservative ones forces net results microscopic connection forces microscopic conservative forces described detailed treatment statistical mechanics closed systems forces act change internal energies system associated transfer heat according second law forces necessarily result energy closed systems ordered random conditions increases units measurement unit force newton symbol force required accelerate kilogram mass rate meter second squared corresponding unit force required accelerate mass centimeter second squared newton equal foot pound second english unit force pound force lbf defined force exerted gravity pound mass standard field pound force provides alternative unit mass mass accelerate foot second squared acted pound force alternative unit force different foot pound second system absolute system defined force required accelerate pound mass rate foot second squared units designed avoid constant newton second law pound force metric counterpart commonly newton kilogram force force exerted standard gravity kilogram mass kilogram force leads alternate rarely unit mass metric mass subjected force kilogram force modern system generally sees use purposes expressing aircraft weight jet thrust bicycle spoke tension settings engine output units force include equivalent equivalent lbf ton force force measurement force gauge spring scale load cell
Force