Experiment 4: Friction Laboratory Report
Kathrina A. Salazar, Maria Ysabelle V. V. Santos, Rosa Katrina G. Santos Group 9 College of Rehabilitation Sciences, Uniersit! of Santos "o#as $spa%a, Manila &hilippines Abstract
In this experiment, the laws of friction were verified. They took in considerati consideration on the area of contact, contact, normal normal force, and nature of surfaces in contact when correlated with friction. The effect of air resi resista stance nce on folded folded papers papers was also also observed. 1. Intr Intro odu duct ctio ion n
An auto#obile is an e'a#ple of a #achin #achinee that that coul( coul( not sere sere its its purpos purposee )ithout friction. A car nee(s tires that are (esi (esign gne( e( to #ain #ainta tain in a high high (egr (egree ee of friction to be able to clasp the roa( tightl! an( eentuall! lea( to a stop. *f there is no fricti friction on presen present, t, roa(s roa(s )ill )ill be fille( fille( )ith )ith acci(ent acci(ents. s. "o be able able to un(erst un(erstan( an( #ore #ore about about fricti friction, on, this this e'peri# e'peri#ent ent is (one (one to erif! the la)s of friction, an( obsere the effe effect ct of air air resi resist stanc ancee on fall fallin ing g coffe coffeee filters. 2. Theory
+riction is a force that is e'erte( on an obect that is parallel to the surface, but in (irection it is technicall! opposite )ith the obect. -a) of friction is as follo)s /hen an obect is #oi oing, the friction is proportional an( perpen(icular to the nor#al force 012. Secon(, +riction is in(epen(ent of the area of contact so long as there is an area of contac contact. t. "hir(, "hir(, the coeffi coefficien cientt of static static fricti ction is slightl! greater than the coefficient of 3inetic friction. +ourth, )ithin
rath rather er larg largee li#i li#its ts,, 3ine 3ineti ticc fric fricti tion on is in(epen in(epen(en (entt of eloci elocit! t!.. -astl! -astl!,, fricti friction on (epen(s upon the nature of the surfaces in contact. +orce is the cause of a change in #otion, or technicall! it is the obect4s #ass #ultiplie( to its acceleration )hich #eans that that forc forcee is pres presen entt )hen )hen t)o t)o obe obect ctss interact or is in the act of push or pull. "here are 5 #ain t!pes of force na#el!, contact force an( action6at6a6(istance. "he for#er is the force that results )hen the t)o obects are ph!sicall! in contacts )hile the latter is the e'act opposite. 1e)ton4s +irst la) states that 7An obect at rest sta!s at rest an( an obect in #otion sta!s in #otion )ith the sa#e spee( an( in the sa#e (irection unless acte( upon b! an unbalance( force force.8 .8 /hile the secon( la) la) stat states es the the rela relati tions onshi hip p of an obe obect cts s #ass #ass m, its acceleration a, an( the applie( forc forcee F is F = ma. ma. Acceleration an( force are ectors. An( in this la) the (irection of the force ector is the sa#e as the (irection of the acceleration ector. -astl!, the thir( la) states that for eer! action there is an e:ual an( opposite reaction. Stat Statiic an( an( Kine Kineti ticc force orce is the coefficient of friction that states the leel of friction e'hibite( b! the interaction of the t)o obects. obects. Static Static +riction +riction is the force force of fricti friction on is greate greaterr than than the applie( applie( force, force, )hil )hilee 3ine 3ineti ticc fric fricti tion on is appl applic icat atio ion n of contin continuous uous force after after the start start of #otion #otion fro# its rest. "he for#ulas use( are
μ
S
μ
maximum static friction ; normal force
;
K
kinetic force normalforce
3. ethodo!o"y
"he #aterials use( in this e'peri#ent )ere the spring balance, bloc3 of )oo(, set of )eights, san( paper, plastic coer, )oo(en boar( an( papers. Actiit! < )as about friction an( area contact. =ere the! place( the )oo( bloc3 on top of the )oo( boar(. Using a spring balance, the! pulle( the bloc3 an( recor(e( )hat #easure#ent the bloc3 #oe( an( )hat #easure#ent it ha( to sta! in to 3eep #oing. Actiit! 5 )as on friction an( nor#al force. "he! use( the sa#e proce(ure )ith Actiit! < but this ti#e the! a((e( <>>g per trial for ? ti#es. /ith this the! (eter#ine( the coefficient of static friction an( coefficient of 3inetic fiction per trial. Actiit! @ )as friction an( nature of surfaces in contact. "he surfaces the! use( )ere plastic coer an( paper on )oo( boar(. +ro# these the! got the #a'i#u# static friction an( 3inetic friction. Actiit! ? the! h!pothesize( the effects of lubricant such as bab! oil an( po)(er. +or the last actiit! the! use( a #otion (etector to be able to recor( the air resistance pro(uce(. +or eer! trial the! )oul( a(( another fol(er paper on top of the other an( repeat the proce(ure.
ropping one filter on top of the #otion (etector
Measuring f s#a'
/oo( )ith ?>>g
the force e'erte( to 3eep an obect that is alrea(! in #otion. Actiit! 5 /eight of bloc3; 5.5 ne)tons f s#a' >.D < <.B <.D
/oo( on cartolina
f K >.B >.D <.5 <.?
S >.D >.E >.E@ >.?E
*t can be seen that the heaier the loa( gets, the greater the a#ount of force is nee(e(. "he coefficient of friction sho)s the relationship bet)een the force bet)een obects an( the nor#al force bet)een obects. +ro# the table aboe, the alues of S an( K are close, but )hen co#pare(, the alues of S are relatiel! higher. Actiit! @ Surfaces in Contact /oo( on plastic coer /oo( an( )oo( /oo( an( san( paper /oo( an( plastic coer 4. Resu!ts and #iscussion /oo( an( cartolina Actiit! < Area < 5 @
fs#a' >.B >.B >.B
f K >.? >.? >.?
"he #ini#u# force nee(e( to start the #otion of the bloc3 of )oo( is >.B ne)ton. "his force is also e:ual to the #a'i#u# static friction. /hen pulle(, the force nee(e( to #oe the bloc3 continuousl! is >.? ne)ton. "hrougout the three trials, the #easure#ents obtaine( )ere the sa#e. "he static friction is greater than 3inetic friction because the a#ount of force nee(e( to get an obect #oing fro# rest is greater than
fs#a' >.B >.D >.B >.D
"he f s #a' an( f K are the largest )hen )oo( an( san( paper, an( )oo( an( cartolina are rubbe( together. +riction (epen(s on the nature of surfaces in contact. "he table aboe sho)s that rubbing )oo( an( san( paper together generates #ore friction than rubbing )oo( an( )oo( together. "he s#oother the surface, the lesser friction it generates6 lesser friction #eans it is har(er to stop. Actiit! ? "he group pre(icte( that the act of rubbing t)o bare han(s together for < #inute (oes not pro(uce the sa#e a#ount of heat co#pare( to rubbing t)o han(s )ith
f K >.? >.B >.? >.B
the application of oil or lotion. Accor(ing to the group, the latter pro(uces #ore heat, using the concept of the bo(! #assage as reference. /hen a #asseuse applies a particular a#ount of oil an( rubs her han(s together, heat is generate(. Actiit! E er of +ilters < 5 @ ? E
"er#inal Velocit! 6>.D 6<.>
Starting a #otion of a hea! bo' re:uires a greater force rather than 3eeping it #oing at a constant spee( because )hen so#ething is #oing it is easier to #aintain its #otion S:uare of "er#inal Velocit! rather that starting fro# rest.
As the nu#ber of filters increases, the ter#inal elocit! increases. +ro# the e'peri#ent, it can be foun( that air resistance is proportional to the elocit! of the falling obect hea! obects hae a higher ter#inal elocit! than light obects. $. %onc!usion
"he group )as tas3e( to (o fie 0E2 (ifferent actiities, to 3no) the friction an( it4s area of contact, friction an( it4s nor#al force, friction an( the nature of surfaces in contact, effects of lubricant an( air resistance. /hich are the la)s of ph!sics in application for#. An( the air resistance is proportional to the spee( so if it4s fast it is then the sa#e )ith s:uare( air resistance that is obsere( in the last actiit!. "he results sho)e( that as )e increase the nu#ber of papers the spee( increases because the air resistance #ini#izes that cause the s:uare( ter#inal elocit! to increase. An( there is reall! an effect in the lubricant, li3e for oil an( lotion. Hil has a propert! that e'hibite( a #ore hot nature )hen rubbe( continuousl! that lotion an( our bare han(s (on4t hae. &. App!ications
1. 'hich (i!! re)uire a "reater *orce: to start the motion o* a hea+y box or to ,eep the box mo+in" (ith constant speed-
2. 'hy is it di**icu!t to (a!, (ith ne( !eather so!es on a po!ished *!oor-
"he effect of the polish in the floor is the re(uce( a#ount of friction present )hen an obect contacts the floor. /al3ing )ith a ne) leather shoes #a3es it (ifficult because the untouche( propert! of the shoes #a3es it slipper! an( the #ini#ize( a#ount of friction fro# the floor is not goo( for slipper! te'tures. 3. o( can an ad/ustab!e inc!ined p!ane be used to measure the coe**icient o* static *riction and coe**icient o* ,inetic *riction.
"o calculate Is , gra(uall! increase the slope of the incline( plance until the obect first begins to sli(e (o)n the plane. Is is (eter#ine( b! the angle of the incline( plane. "he tangent of the angle at )hich a bloc3 sli(es (o)n on an incline at constant elocit! gies I3 . 0, tan , 4. The coe**icient o* static *riction and coe**icient o* ,inetic *riction bet(een a re*ri"erator and the *!oor are .4$ and .35 respecti+e!y. The re*ri"erator (ei"hs 165 *ind the hori7onta! *orce needed to a8 start the motion o* the re*ri"erator b8 to ,eep the re*ri"erator mo+in" at constant speed once it started mo+in". I* a hori7onta! *orce o* 46 is app!ied5
(hat (i!! happen to the re*ri"eratorIn this situation5 (hat is the +a!ue o* *rictiona8
us x fN fsmax =
>.?E ' <>>> ; ?E> 1 "o start the #otion of the refrigerator !ou )oul( nee( to appl! the force of ?E> 1. b8
httpsJJ))).#su.e(uJcourseJ3inJ@@>Jfrcition .ht# 5. Static Kinetic +riction. 0n.(.2. Retriee( +ebruar! >B, 5>>5.)eb.( irJbenLto)nsen(JStatican(Kinetic+riction.ht # @. 1e)tons -a)s. 0n.(.2. Retriee( +ebruar! >B, 5>
uk x fN fk =
?. Ser)a!, R., Chris, V. 05><52. College &h!sics 09th e(.2. USA Charles =artfor(. >.@D ' <>>> ; @D> 1 "o 3eep the refrigerator #oing at a constant spee( !ou )oul( nee( to appl! the force of @D> 1.
*f a horizontal force of ?>>1 is applie( the refrigerator )ill not #oe since the force applie( is less than the )eight of the refrigerator. "he static friction )ill still be ?E> 1 since the refrigerator is not #oing. 9. Re*erences
<. "=$ +*V$ -A/S H+ +R*C"*H1. 0n.(.2. Retriee( +ebruar! >B, 5>
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