ocr a level physics unit 1-2 definitions

8/10/2019 OCR A LEVEL PHYSICS UNIT 1-2 DEFINITIONS

http://slidepdf.com/reader/full/ocr-a-level-physics-unit-1-2-definitions 1/57

• 1

Scalar

sandvector s

Ascalarquantityhasma

gnitudeonly.Examples:mass,distan

• 2

Kine

matics

Theaveragespeedv of anobjectis

(totaldistance!time.Theinstantaneoussp



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



hasma

gnitudeanddirection.Examples:velocity,dis

placement,acceler ation,force,"ei

esultant

distancemovedin agivendirection.

• %el

ocityv istherateofchangeofdis



ght,gra

vitationalfieldstrength,curr ent.

• The

resultant(oreffectivecombinationof

placeme

nts:

v # $s!$t

• Acc

eler ation aistherateof

changeofvelocityv : a# $v ! $t



t"ovec

torscanbefoundusingatriangle,par allel

ogr amorrectangletorepr



esentthe

min adiagram.

• A

vectorV inclinedatanangle θ tothehori&ontalhas



componen

ts:hori&ontalcomponent #V cosθ andvert

icalcomponent #V sinθ



• 4

Linearmotion

'ormotionatconstantvelo

city"eusetheequatio



• 3

Motio

ngraphs

Themotionofobjects isoftenrepr esentedby



n v = x !t

• 'or

motionatconstantacceler ation"eusethesefiveequations:v #u at ts# )



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



lacement

–time graphrepr esentsvelocity: v # $s!

$t • The

gradientof avel ocit

hrough

theair,thehori&ontalandverticalmotionsareind

ependent.

• The

projectilethe



y–tim

e graphrepr esentsacceler ation: a# $v ! $t

• The

areaunder avel ocit y–tim

reforemo

ves"ithaconstanthori&ontalvelocity,and"ith

verticalvelocitychangingdu



e gra

phrepr esentsdisplacement.

e tothe

acceler ation of freefall.

• 5

Force

'orces

al"ayso

• 6

Resistivefor

cesan



ccur inequ

alandoppositepair s,actingont"obodies.

• +h

enforcescausetheveloc

dter

minalvelocity

bjectsmovingthroughairor

liquidsexperienceairresistance



ity ofan

objecttochange:resultantforce #mass

-acceler ation16F =maThene"t

orvisc

ousdrag.

• The

magnitudeofthedragforcedependsonthemedium,thesi&eof



on isthat

force"hichgivesamassof /ganacc

eler ation of m

s0*.

• +ei

ght(i

theobj

ectandthespeedoftheobject.

• 1ra

gincr eases"ithspeed.

• 'or

anobjectfalling



n 2 #ma

ss(in/g-gravitationalfieldstrength

(in2

/g0

.

• The

equation F =ma cannotb

in airund

ergravity,thedragincr easesuntilitequals

the"eight.Theresultantforce



e usedfor

particlestravelling atver yhighspeeds,

becausetheirmassincr eas

andthe

acceler ationareboththen&er o3theobj

ectcontinuesat aconstantter min



es"ith

energy.

alvelo

city.

•

!"#ili$ri#m

Thecentreofgravityofanobjecti

• %

&arsaf ety

Thethin/ingdistance isthedistancetra



s thepoi

nt"hereits"hole"eightmaybeconsid

ered toact.

• The

momentof afo



velled"hile

thedriverreacts.Thin/ingdistance #(reactio

ntime -(speedofthevehicle

• The

b



rceabo

ut apoint #force -per pendicular distancefro

mtheforcelinetoth

ra/ingdist

ancedependsonthemassofthevehicle

andtheefficiency of thebra/es,



epoi

nt.• A

coupleis apair offorcesthatareequalinmagnitudebutactinoppo

and ispro

portionaltothesquareofthespeed.

• Air

bagsandcrumple&onesincr ease



sitedire

ctionsproducingrotation.Thetorqueof acou

ple#oneforce -per pen

thetim

eanddistanceta/entocometorest,

andther efor ereducetheimpactfor



dicular dist

ancebet"eenthem.

• The

principle of moments:forabody inequilibri

ces.

• 4lo

bal5ositioning6ystemsusethetrilaterationtechnique.



um,su

mofcloc/"isemomentsabout apoint #su

mofanticloc/"isemoments.



• '

(or)andener gy

+or/do

ne#force-distance

movedint

• 1*

+o,er-density-pr ess#re

5o"er isthe

rateof"or/ing.5



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



• 11

!lasti

cmaterials

8oo/e9sla":for aspr ingormaterial"hichisstr etch

• 12

.he

/o#ngmod#l#s

Tensilestr essis

for ceF perunitcrosssectional



ed upto

itselasticlimit,theextensionispr

oportionaltothetension.

• Th

area A.

6tr ess #F ! A

• Te

nsilestr ainisexten

sion $ x perunitlength.6tr ain



• 13

&har

geandc#rrent

Electr iccur rentisa

basequantitydef inedinter m

• 14

&har

gecarrier s

;n ametal,char geiscar

riedbymovementoffreeelect



s ofthe

for cebet"eent"olong,parallel,cur

rentcar ryingconductors.

•

rons3in

anelectr olyte,char geiscar riedby

positiveandnegativeions.

• Th

e c



<urrent

! israteofflo"ofchar ge.! # $"!

($t $"# ! $t <urrentismeasur ed

u

onventi

onalcur rentisthedir ectionin"hich

positivechar ges"ouldm



singan

ammeter connectedinser ies.

•

coulom# (<isthequantityofcharg

ove.Th

eelectr oncur rentisintheopposit

edir ection.

• <o

nductors,sem



e"hi

chpasses"henacur rent of amper

epassesforatimeofsecond.

• Th

e

iconduct

orsandinsulator shavediff er entnu

mbersnofchar gecar rier



element

arychar geise #.=> ->0?

<.This

isthesi&eofthenegativechar

s peruni

tvolume.

• ;n

ametal"ir eofcrosssectionalar ea A "ithelectr on



ge ofan

electr onandthepositivechar geof

apr oton.

smo

ving"ithdrif tvelocityv ,thecur re

ntis ! #nAve



• 15

+ote

ntialdif fer enceande0m0f0

Thepot

entialdiff er encebet"eent"opoin

• 16

Resis

tance

Thefunctionsofaresistor

inacir cuitar etocontr olthe



ts isdef

inedasthe"or/doneinmovinguni

tchar gebet"eenthosepoints. V #

current,

andtodissipateener gyinheating.

• Theresistance$ ofaconducto



• 1

&#rre

ntvoltagechar acter istics

The ! V ch

ar acteristic(gr aphfo

• 1%

Resis

tivity

Theresistivityofaconductor

oflength,crosssectio



r afix

edresistoratconstanttemper ature

isastr aightlinethr oughthe

nalar

ea A andresistance$ is % #$

A!.Thus$= %! A

• Th

eunit of resistivityis



• 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



*$ #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



• 21

Resis

tor sincir c#its

'orthr eeresistorsin

ser ies:$ s #$ $ * $

• 'o

r

• 22

+ote

ntialdividers

A p.d.Visappliedacr

osst"oresistors$ and $ * inse



threeres

istorsinparallel:!$ p#

!$ !

$ * !$

• A

cellhasinter nalre

ries.Th

ep.d.sacr osstheresistorsar eV

#V $ !($ $ *andV * #V $ *!($

$ *

• Th

e



• 23

(ave

motion

Apr ogressive"avetransf

ersener gyfromoneplacetoan

• 24

(ave

meas#rements

Theamplitude A

ofa"avemotionisthemaximum

disp



other,but

themediumonlyvibratesoroscillate

s.• All

"avemotions,includ

lacement

ofthevibratingmedium,orthemaximu

mvalueofanoscillatingsi



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



llpo

ssibledir ectionsintheplaneperpen

diculartothedir ectionof"a



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



antph

asediff er encebet"eenthem.

• <o

nstructiveinterf er enceoccur s"h



• 2'

Stati

onar y,aves

6tationary(standing

"avesar efor med"hent"oide

nt

• 3*

+hot

ons

Aphotonisonequantumof

ener gyofelectr omagneticradiat



ical"a

vestravellinginoppositedir ect

ionsar esuperposed.

• 2o

desar efo

ion.

• Th

eener gyofaphotonofradiatio

noffrequency is* #=c !

"her e



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



itesh

o"sthattheyhave"avepr operti

es.1if fractionofelectr onscansh

o

ocr a level physics unit 1-2 definitions

Documents