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PH105001, Fall2010

Instructor:Dr.

Nobuchika

Okada

GraduateTA:UppalaiahErugu

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Coursewebpage:

http://feynman.xsrv.jp/2010fall/

OfficeHours:

Room

320

A

TRF11:0012:00orbyappointment

Ihaveanopendoorpolicy. Youcanvisitmeanytime

Syllabus,ClassSchedule,Lecturenotes,etc

arepostedonthiswebpage

E

Mail:

okadan@ua.eduDoNothesitatetoemailme!

Anyquestionsandcommentsarewelcome!

Homeworkassignment

Homework (HW3)onQuest

Duedate:

Sep.

22,

23:00

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TodaysPlan

LectureChapter6:CircularMotion

Exercisefor1st Exam(Sep.24)

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Chapter6 (Contd)

CircularMotion

and

OtherApplicationsofNewtonsLaws

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MotioninthePresenceofResistiveForces

InChapter5,wedescribedtheforceofkineticfriction,but

completelyignoredanyinteractionbetweentheobjectand

themediumthroughwhichitmoves

Nowweconsidertheeffectofthatmedium,whichcanbe

eitheraliquidoragas

Themediumexertsaresistiveforceontheobjectmoving

throughit,suchastheairresistanceandtheviscousforce

actingonobjectsmovingthroughaliquid

Thedirectionoftheresistiveforceisalwaysoppositeto

thedirectionof theobjectsmotionrelativetothemedium

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Themagnitudeoftheresistiveforcecandependonspeedina

complexway,andhereweconsideronlytwosimplifiedmodels

Model1:ResistiveForceProportionaltoObjectVelocity

,wherebisaconstantwhosevaluedependson

thepropertiesofthemediumandontheshapeanddimensionsoftheobject

Letusconsiderafreefallofaobjectinthemedium

Fromthisdifferentialequation,theacceleration

becomeszero

when

the

speed

of

sphere

approaches

itsterminalspeed

Becausein

this

case,

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Mathematics: problemtosolvethedifferentialequation

Solutionswhen

we

set

v=0

at

t=0,

Check:take1st derivative

Useaformula

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Model2:ResistiveForceProportionaltoObjectSpeedSquared

Forobjectsmovingathighspeedsthroughair,suchasan

airplane,skydivers,cars,andbaseballs,theresistiveforceis

reasonablywellmodeledasproportionaltothesquareof

thespeed

dragcoefficient

densityofair

crosssectional

area

of

the

moving

objectmeasuredinaplane

perpendicularitsvelocity

Again,forafreefalling,wehave

Wefind

the

terminal

speed

as

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Forafreefalling,wehave

Wefind

the

terminal

speed

as

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Announcement

1st HourExam (Chapter16)isscheduledon

Sep.

24

(Fri)

Closedbooktest

(1)Youareallowedtouseonecheatsheet

(lettersize,youcanwriteformulasetc.onbothsides.prepareacheatsheetifyouneed)

(2)You

need

acalculator

Allaremultiplechoicequestions

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Maintopics:

1DMotion

Definitionsofposition,velocity,acceleration,etc.

Motionwithaconstantvelocity/acceleration

Free

fall

motion

2DMotion

Vectors

Projectilemotion

Uniformcircularmotion

Newtonslawsofmotion&Applications

Freebody

diagrams

Inclinedsurface,(half)Attwoodmachineetc.

Frictionforces

Nonuniform

circular

motion

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Reviewlecturenotes http://feynman.xsrv.jp/2010fall/

Examples&ExerciseProblems

Summaryofeachchapter

definitions

of

new

physics

quantities

quickreviewswhatyouhavelearned

Tips

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Exercisefor

1st Exam

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TheExamgoeslikethis

1.(10

points

each)

AblockofmassM isacceleratedalongtheinclinebyaforceofmagnitude

F,shownbelow. Thefrictionalforceontheblockexertedbythesurfacehasmagnitudef.

(A)Whatisthemagnitudeoftheacceleration?

Answer:________

(B)Which

of

the

following

.

?

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TheExamgoeslikethis

1.(10

points

each)

AblockofmassM isacceleratedalongtheinclinebyaforceofmagnitude

F,shownbelow. Thefrictionalforceontheblockexertedbythesurfacehasmagnitudef.

(A)Whatisthemagnitudeoftheacceleration?

Answer:________

Somespace

Somespace

(B)What

is

..?

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Nowyoutrytofindthesolutiontothisproblem

1.(10

points

each)

AblockofmassM isacceleratedalongtheinclinebyaforceofmagnitude

F,shownbelow. Thefrictionalforceontheblockexertedbythesurfacehasmagnitudef.

(A)Whatisthemagnitudeoftheacceleration?

Answer:__3_____

Youmaydrawfreebodydiagram

Wrong!

Idonotknowwhyyouarrivedatthewronganswer,butI

seethefreediagramiscorrectandyouwerealmostthere

giveyou,

say,

5points

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TheExamgoeslikethis

1.(10

points

each)

AblockofmassM isacceleratedalongtheinclinebyaforceofmagnitude

F,shownbelow. Thefrictionalforceontheblockexertedbythesurfacehasmagnitudef.

(A)Whatisthemagnitudeoftheacceleration?

Answer:________

Thisspaceistowriteyourprocess

Inthesameway,yougotawronganswer,buttheformulas

youshowed

space

is

correct,

you

may

earn,

say,

5points.

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ProjectileMotion

Projectilemotion 1DmotionwithaconstantvelocityinxdirectionFree

fall

motion

in

ydirection

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ReadingassignmentfornextTuesdayclass:

Serwayand

Jewett,

Chapter

7

Homeworkassignment

Homework (HW3)onQuest

Due

date:

Sep.

22,

23:00