The physics most important to 20th Century. The most useful interactions - Electricity & PHYSICS. » Physics on the atomic scale.

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Ruth Hudson
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1 Physic301 Where o in Tomorrow s Assignmen Class Web Page hp:// Class normaion» Syllabus can be downloaded rom web» Schedule» Grading Lecure noes Te problem soluion oulines Oice hours & addresses Announcemens neresing physics links Read Syllabus Need o buy» Te (booksore)» Lab Manual(web or booksore)» Lab Journal (booksore) Beore Tomorrow Read Syllabus Careully Read Te Chaper 1, 2 Do problems Chaper 1 Read Compeen Problem Solver Chap. 1, 2 Beore ne Monday Read Compeen Problem Solver Chap. 3 Do Te Problems Chaper 2 Take Prelab Compuer Quiz» Compeen Problem Solver(booksore) Read Assigned Problems in Lab 1 and» nde Cards (booksore) do predicions and mehods quesions Quesions abou course (omorrow) 1 2 Course Srucure Lecures My job Tell you why Show you how Trying o undersand The Universe Physics Your job Read he e beore coming o lecure Connec lecures o wha you know Ask i i doesn make sense o you Your neighbor Me Paricipaing in Lecures is no enough You need o pracice o undersand Observe Objecs Their Moion ner neracions The Universe operaes he same way or Everyhing Everywhere Pracice in many dieren siuaions Discussion secion Laboraory By yoursel Oice hours Sudy group Organized eedback 5 4 Words do no always mean he same or everyone. Careul deiniions Mahemaics nroducion o Physics or Engineers & Scieniss Undersand he behavior o everyhing ormulae Theories o Predic Behavior» Qualiaive» Quaniaive Develop Problem Solving Sraegy Develop Technical Communicaion Skills Physic301 Behavior o objecs when hey inerac Physic302 The mos useul ineracions Elecriciy & Magneism Physics 2503 The physics mos imporan o 20h Cenury echnology» Elecromagneic waves» Opics» Physics on he aomic scale 3 PHYSCS Goal: Deermine he ineracions beween he objecs Why? Curiosiy and undersanding Conrol One eec o an ineracion: ineracing objecs change heir moion We need o precisely describe he eec o an ineracion on he moion o an objec. We need o precisely describe he moion o an objec. We consruc heories abou how i all works. Physics is a consruc o he mind. Physics is no TRUTH Physics works very well 6 1

2 Physics is abou everyhing. Divide our Universe ino: Objecs neracions Objecs have properies mass, charge, densiy... Objecs have relaionships o oher objecs posiion, velociy, acceleraion neracions have properies srengh, variaion,... Groups o objecs sysems properies descripions 7 DESCRBE THE RESULTS GENERALZE Make a model or heory QUALTATVE DESCRPTON An objecs moves (changes posiion) only when a push or pull (orce) is applied o ha objec. The change o posiion in a given amoun o ime (speed) is greaer i he applied orce is greaer. QUANTTATVE DESCRPTON (Mah Translaion) (Speed) = (orce) (A Consan Somehing) CHECK orce = 0 han Speed = 0 orce increases, hen Speed increases S = k Why no S = k, S = k 2, or S = k 3? 10 Your Theory o Physics Everyone has one You have survived in he Universe Using Your Theory o Physics Your personal Theory o Physics Mosly correc bu Some is no This course is abou eamining Your Theory o Physics Correc i when necessary Make i more useul wih powerul ools Problem solving Communicaion Mahemaics An eample o how o do i comes ne Go To he Laboraory To decide which heory we wan, we mus measure S as a uncion o. We mus describe how o measure hese quaniies, and his descripion becomes he deiniion o he quaniy neracions & Moion The EperimenSar wih an objec a res on a able. The objec doesn move. iner There is no ineracion. Now cause an ineracion by pushing he objec. The objec moves. The harder you push, he aser i moves. You sop pushing. The objec sops. iner Their is no ineracion. 9 PREDCTON Wha do we epec he resuls will be when we make he measuremens? S S = k S S = k S S = k 2 or wha values o S or do we make our measuremens? 12 2

3 Beore we begin o do his ime consuming eperimen, can you hink o any observaion you have already made ha disagrees wih all o he heories o moion we made. Plan or 1301 Careul descripion o moion Posiion, ime Speed, velociy Average, insananeous Acceleraion Theory o ineracion orces Energy Momenum Torque Angular momenum Applicaions Use only he mos imporan equaions. No oher ormulas allowed. Mah Calculus pracice Use in Physics beore mah class Problem Solving Logical Procedure Well Communicaed Throwing Can we eplain he moion o an objec on a able and an objec hrown hrough he air using a single heory? We will have eplained an even i we can predic he moion compleely. Does he ball s moion agree wih he heories o he ype S = k? n his case we mus predic he objec s pah (rajecory) and is speed along ha rajecory or a given ineracion. Why or why no? Eamine your personal se o physics heories. Predic (draw) he ball s rajecory. 14 Describe he behavior o he ball s speed as i moves along he rajecory. 15 Describing Moion Eample problem Sar wih simple siuaions Sraigh line moion Eamine your eising knowledge Careul deiniions Useul mahemaics Try solving he ollowing problem using a logical and wellcommunicaed procedure. Aer solving he problem Careully review he meaning o Speed Velociy Acceleraion While waiing in he denis s oice he only hing here is o read is one o hose awul puzzle books. Since you are bored, you read he ollowing brain easer. Two rains leave dieren saions 80 km apar and ravel oward each oher on a sraigh rack. One rain has a speed o 80 km/h, and he oher has a speed o 160 km/h. A very as insec leaves he slower rain and heads oward he aser rain a a speed o 240 km/h. Upon encounering he second rain, i urns around and jus as rapidly reurns o he irs rain. coninues hese maneuvers unil i is squashed beween he wo rains when hey collide. How ar did he insec ly? You know physics so you should be able o solve i. Average 17 Apply a problem solving sraegy. 18 3

4 Problem Solving Technique Used by epers in all ields ProblemSolving Sraegy or Physics Problems How o solve a problem you don know how do Recognize he Problem Wha s going on? Describe he problem in erms o he ield Wha does his have o do wih...? ocus he Problem Visualize he siuaion. Draw a skech. Wha is he quesion? Wha general approach may be work? Plan a soluion Can use wha know o ge an answer? Eecue he plan Ge an answer Physics Descripion Deine he relevan quaniies: Diagrams Coordinae sysem Knowns, unknowns deniy he arge quaniy(ies) Evaluae he soluion Can his be rue? 19 Assemble appropriae ools (equaions). 20 Eample problem Sep 1: ocus he problem While waiing in he denis s oice he only hing here is o read is one o hose awul puzzle books. Since you are bored, you read he ollowing brain easer. Two rains leave dieren saions 80 km apar and ravel oward each oher on a sraigh rack. One rain has a speed o 80 km/h, and he oher has a speed o 160 km/h. A very as insec leaves he slower rain and heads oward he aser rain a a speed o 240 km/h. Upon encounering he second rain, i urns around and jus as rapidly reurns o he irs rain. coninues hese maneuvers unil i is squashed beween he wo rains when hey collide. How ar did he insec ly? You know physics so you should be able o solve i. Visualize 80 km/h 160 km/h 240 km/h 80 km Quesion: Wha is disance insec ravels in ime i akes rains o collide? Approach: inseclies Average speed = insananeous speed Trains have consan velociy Average velociy = insananeous velociy Use deiniion o average speed. Apply a problem solving sraegy. Use deiniion o average velociy Plan a Soluion Consruc chain o equaions leading rom arge quaniy. Check unis o algebraic answer. Eecue he Plan Use given values o calculae arge quaniy. Evaluae he Soluion s he answer properly saed? s he answer unreasonable? s he soluion complee? 21 Sep 2 : Describe he Physics Moion Diagram: v v B A vb v A o, o, 1, o v o = 0 o = 0 =? =? 1 = 80 km v A = 80 km/h v B = 160 km/h v = 240 km/h Targe Quaniy: = disance inseclies in ime o Quaniaive Relaionships: since insec speed is consan o v A = o since rain A velociy is cons. o v B = 1 o since rain B velociy is cons. 24 4

5 Sep 3: Plan he soluion unknowns ind o [1] ind v A = o o v A = [2] ind v B = 1 o v B = 1 [3] Generalizaion Does he insec s disance always equal he iniial separaion o he rains? Suppose ha he insec s speed were 120 km/hr The answer is an ACCDENT o he numbers no a general principle. The insec s disance is NOT necessarily equal o he iniial separaion o he rains! ( v A v B ) = Always gives insec s disance Sep 4: Eecue he Plan Sarrom end o plan and work backwards o arge [3] v B = 1 ind v B 1 = [2] v A = ind v A = v B 1 v A v B = 1 ( v A v B ) = 1 [1] ind = 1 ( v A v B ) 1 ( v A v B ) ( v A v B ) = 26 ( v A v B ) = check unis: ( km / h ) ( km ) ( km / h km / h ) = km ( 240 km / h ) ( 80 km ) ( 80 km / h 160 km / h ) = 80 km = Evaluae Soluion: Properly saed? The disance is in km (ok unis) Unreasonable? The disance is he same as iniial separaion o rains. Surprising bu no an unreasonable disance. Complee? The disance was waned (ok) 27 5

Physics Notes - Ch. 2 Motion in One Dimension

Physics Notes - Ch. 2 Motion in One Dimension Physics Noes - Ch. Moion in One Dimension I. The naure o physical quaniies: scalars and ecors A. Scalar quaniy ha describes only magniude (how much), NOT including direcion; e. mass, emperaure, ime, olume,