ocr a level physics unit 1-2 definitions
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8/10/2019 OCR A LEVEL PHYSICS UNIT 1-2 DEFINITIONS
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• 1
Scalar
sandvector s
Ascalarquantityhasma
gnitudeonly.Examples:mass,distan
• 2
Kine
matics
Theaveragespeedv of anobjectis
(totaldistance!time.Theinstantaneoussp
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ce,tim
e,speed,density,energy,po"er ,temper atur
e,charge,resistance,p.d.
• A
vectorquantity
eed v is
therateofchangeofdistance x :v # $ x ! $t
• The
displacement sofanobjectisther
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hasma
gnitudeanddirection.Examples:velocity,dis
placement,acceler ation,force,"ei
esultant
distancemovedin agivendirection.
• %el
ocityv istherateofchangeofdis
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ght,gra
vitationalfieldstrength,curr ent.
• The
resultant(oreffectivecombinationof
placeme
nts:
v # $s!$t
• Acc
eler ation aistherateof
changeofvelocityv : a# $v ! $t
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t"ovec
torscanbefoundusingatriangle,par allel
ogr amorrectangletorepr
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esentthe
min adiagram.
• A
vectorV inclinedatanangle θ tothehori&ontalhas
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componen
ts:hori&ontalcomponent #V cosθ andvert
icalcomponent #V sinθ
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• 4
Linearmotion
'ormotionatconstantvelo
city"eusetheequatio
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• 3
Motio
ngraphs
Themotionofobjects isoftenrepr esentedby
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n v = x !t
• 'or
motionatconstantacceler ation"eusethesefiveequations:v #u at ts# )
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displace
ment–time gr
aphsorbyvel ocit y–time graphs
.• The
gradientof adis p
(u +v t t
s #ut )at *2v * #u* *ass =[(v+u)]/ 2]t
• 'or
aprojectile,suchasagolf ballmovingt
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lacement
–time graphrepr esentsvelocity: v # $s!
$t • The
gradientof avel ocit
hrough
theair,thehori&ontalandverticalmotionsareind
ependent.
• The
projectilethe
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y–tim
e graphrepr esentsacceler ation: a# $v ! $t
• The
areaunder avel ocit y–tim
reforemo
ves"ithaconstanthori&ontalvelocity,and"ith
verticalvelocitychangingdu
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e gra
phrepr esentsdisplacement.
e tothe
acceler ation of freefall.
• 5
Force
'orces
al"ayso
• 6
Resistivefor
cesan
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ccur inequ
alandoppositepair s,actingont"obodies.
• +h
enforcescausetheveloc
dter
minalvelocity
bjectsmovingthroughairor
liquidsexperienceairresistance
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ity ofan
objecttochange:resultantforce #mass
-acceler ation16F =maThene"t
orvisc
ousdrag.
• The
magnitudeofthedragforcedependsonthemedium,thesi&eof
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on isthat
force"hichgivesamassof /ganacc
eler ation of m
s0*.
• +ei
ght(i
theobj
ectandthespeedoftheobject.
• 1ra
gincr eases"ithspeed.
• 'or
anobjectfalling
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n 2 #ma
ss(in/g-gravitationalfieldstrength
(in2
/g0
.
• The
equation F =ma cannotb
in airund
ergravity,thedragincr easesuntilitequals
the"eight.Theresultantforce
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e usedfor
particlestravelling atver yhighspeeds,
becausetheirmassincr eas
andthe
acceler ationareboththen&er o3theobj
ectcontinuesat aconstantter min
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es"ith
energy.
alvelo
city.
•
!"#ili$ri#m
Thecentreofgravityofanobjecti
• %
&arsaf ety
Thethin/ingdistance isthedistancetra
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s thepoi
nt"hereits"hole"eightmaybeconsid
ered toact.
• The
momentof afo
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velled"hile
thedriverreacts.Thin/ingdistance #(reactio
ntime -(speedofthevehicle
• The
b
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rceabo
ut apoint #force -per pendicular distancefro
mtheforcelinetoth
ra/ingdist
ancedependsonthemassofthevehicle
andtheefficiency of thebra/es,
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epoi
nt.• A
coupleis apair offorcesthatareequalinmagnitudebutactinoppo
and ispro
portionaltothesquareofthespeed.
• Air
bagsandcrumple&onesincr ease
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sitedire
ctionsproducingrotation.Thetorqueof acou
ple#oneforce -per pen
thetim
eanddistanceta/entocometorest,
andther efor ereducetheimpactfor
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dicular dist
ancebet"eenthem.
• The
principle of moments:forabody inequilibri
ces.
• 4lo
bal5ositioning6ystemsusethetrilaterationtechnique.
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um,su
mofcloc/"isemomentsabout apoint #su
mofanticloc/"isemoments.
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• '
(or)andener gy
+or/do
ne#force-distance
movedint
• 1*
+o,er-density-pr ess#re
5o"er isthe
rateof"or/ing.5
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hedi
rectionof theforce. joul
e (7isthe"or /done
or ener gytr ansf er red
o"er#
("or/done!(timeta/en. Apo"er of
"att(#
7 s0isdevelopedif
jou
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• 11
!lasti
cmaterials
8oo/e9sla":for aspr ingormaterial"hichisstr etch
• 12
.he
/o#ngmod#l#s
Tensilestr essis
for ceF perunitcrosssectional
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ed upto
itselasticlimit,theextensionispr
oportionaltothetension.
• Th
area A.
6tr ess #F ! A
• Te
nsilestr ainisexten
sion $ x perunitlength.6tr ain
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• 13
&har
geandc#rrent
Electr iccur rentisa
basequantitydef inedinter m
• 14
&har
gecarrier s
;n ametal,char geiscar
riedbymovementoffreeelect
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s ofthe
for cebet"eent"olong,parallel,cur
rentcar ryingconductors.
•
rons3in
anelectr olyte,char geiscar riedby
positiveandnegativeions.
• Th
e c
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<urrent
! israteofflo"ofchar ge.! # $"!
($t $"# ! $t <urrentismeasur ed
u
onventi
onalcur rentisthedir ectionin"hich
positivechar ges"ouldm
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singan
ammeter connectedinser ies.
•
coulom# (<isthequantityofcharg
ove.Th
eelectr oncur rentisintheopposit
edir ection.
• <o
nductors,sem
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e"hi
chpasses"henacur rent of amper
epassesforatimeofsecond.
• Th
e
iconduct
orsandinsulator shavediff er entnu
mbersnofchar gecar rier
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element
arychar geise #.=> ->0?
<.This
isthesi&eofthenegativechar
s peruni
tvolume.
• ;n
ametal"ir eofcrosssectionalar ea A "ithelectr on
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ge ofan
electr onandthepositivechar geof
apr oton.
smo
ving"ithdrif tvelocityv ,thecur re
ntis ! #nAve
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• 15
+ote
ntialdif fer enceande0m0f0
Thepot
entialdiff er encebet"eent"opoin
• 16
Resis
tance
Thefunctionsofaresistor
inacir cuitar etocontr olthe
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ts isdef
inedasthe"or/doneinmovinguni
tchar gebet"eenthosepoints. V #
current,
andtodissipateener gyinheating.
• Theresistance$ ofaconducto
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• 1
&#rre
ntvoltagechar acter istics
The ! V ch
ar acteristic(gr aphfo
• 1%
Resis
tivity
Theresistivityofaconductor
oflength,crosssectio
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r afix
edresistoratconstanttemper ature
isastr aightlinethr oughthe
nalar
ea A andresistance$ is % #$
A!.Thus$= %! A
• Th
eunit of resistivityis
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• 1'
+o,e
rinelectr icalcir c#its
5o"er & devel
opedinacir cuit is&=V! # !
• 2*
Serie
sandparallelcir c#its
@irchhof f9sfirs
tla":atanycir cuit junct
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*$ #V *!
$ • En
er gy transf err ed#po"er -timee'=&t #!tV
• 'u
se"ir eisma
deo
ion,tot
alcur rentin#totalcur rentout.
Thisisaconsequenceoftheco
nser
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• 21
Resis
tor sincir c#its
'orthr eeresistorsin
ser ies:$ s #$ $ * $
• 'o
r
• 22
+ote
ntialdividers
A p.d.Visappliedacr
osst"oresistors$ and $ * inse
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threeres
istorsinparallel:!$ p#
!$ !
$ * !$
• A
cellhasinter nalre
ries.Th
ep.d.sacr osstheresistorsar eV
#V $ !($ $ *andV * #V $ *!($
$ *
• Th
e
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• 23
(ave
motion
Apr ogressive"avetransf
ersener gyfromoneplacetoan
• 24
(ave
meas#rements
Theamplitude A
ofa"avemotionisthemaximum
disp
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other,but
themediumonlyvibratesoroscillate
s.• All
"avemotions,includ
lacement
ofthevibratingmedium,orthemaximu
mvalueofanoscillatingsi
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25!lectromagnetic,aves
• All electromagnetic "aves travel at the same speed c in a
vacuum or free space. c # .>> - >B m s0
• All em "aves are transverse "aves and can be polarised.
• The "avelengths of visible light range approximately from
C>> nm for violet to D>> nm for red.
• Typical "avelengths for other em radiations are:
gammaarayssultraviolettinfrareddmicro"avessradio>0*
mm>0> mm>0B
mm>0F mm>0*
mm
G>>> m
• 26
+olar
isation
;nunpolarised"avesthe
vibrationofthemediumisina
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llpo
ssibledir ectionsintheplaneperpen
diculartothedir ectionof"a
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2S#perpositionof,aves-diffraction
• The 5rinciple of 6uperposition: if t"o "ave motions are
superposed, the resulting displacement at any point is thevector sum of the individual displacements.
• At any point: intensity ∝ (amplitude of "ave motion*
• 1iffraction is the spreading out of "aves "hen they pass
through an aperture or round an obstacle.
• ;f light of "avelength is incident on a diffraction grating of
spacing d , then a pattern of order n is seen at angle θ"here n # d sin θ
• 2%
nterf
er ence
T"ocoherentsourceshave
thesamefrequencyand aconst
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antph
asediff er encebet"eenthem.
• <o
nstructiveinterf er enceoccur s"h
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• 2'
Stati
onar y,aves
6tationary(standing
"avesar efor med"hent"oide
nt
• 3*
+hot
ons
Aphotonisonequantumof
ener gyofelectr omagneticradiat
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ical"a
vestravellinginoppositedir ect
ionsar esuperposed.
• 2o
desar efo
ion.
• Th
eener gyofaphotonofradiatio
noffrequency is* #=c !
"her e
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31.hephotoelectriceffect
• A negatively charged and freshly cleaned &inc plate "ill
lose electrons if ultraviolet radiation is incident on it.
• 5hotoelectric effect sho"s that em radiation has particle
properties.
• The "or/ function H of a metal is the minimum energy to
release an electron from its surface. The thresholdfrequency is the minimum frequency of radiation to releaseelectrons from the metal9s surface.
• ne photon of frequency may release one electron. The
maximum @E of the electron released is )mv max* # 0 H
• 32
(ave
particled#ality-spectra
Thediff rac
tionofelectr onsbygr aph
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itesh
o"sthattheyhave"avepr operti
es.1if fractionofelectr onscansh
o
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