Fall 2009 PHYS 172: Modern Mechanics Lecture 1: Matter & Interactions Read: Ch 1.1-1.4 Pick up the handouts: Syllabus, Schedule Quick CHIP & WebAssign These will be discussed in more detail on Thursday, after you have had a chance to read them. To do AS SON AS POSIBLE: 1. Obtain the textbok (at campus bokstores; used boks are OK). 2. Obtain the new PHYS 172 Laboratory Manual (from bokstore). 3. Obtain an iClicker audience response remote (not a CPS pad). 4. Register for WebAsign, the on-line homework service. 5. Register your iClicker on CHIP, your on-line PHYS 172 gradebok. 6. Click on the course URL for any late anouncements, etc: ww.physics.purdue.edu/academic_programs/courses/phys172 (or poke around Physics home page, ww.physics.purdue.edu During the first week you will: ?Attend the two scheduled lectures, on Tuesday and Thursday. ?Attend the Recitation session assigned to you by the Registrar. ?Log in to WebAssign and complete ?HW #1? by midnight Thursday Aug 27. ?Lab meetings will not be held during the first week. Instead, log in to WebAssign and complete ?Lab #1 Orientation? by Tuesday, Sep 1st. The three evening exams this semester (All in Elliot Hall): Exam 1: Tuesday, Sep 15 8:00-10:00 pm Exam 2:Wednesday, Oct 148:00-10:00 pm Exam 3:Tuesday, Nov 178:00-10:00 pm Note that the first exam will be coming up soon. Note: ? Lectures ? Recitations ? Labs ? Evening Exams Note: READING " T T J H O N F O U T 190019201940196019802000 Milestones from the last century of physics: Discovery of x-rays (1895) Radioactivity (1896-1902) Atoms - electrons (1896), nuclei (191), neutrons (1932) Relativity (Einstein 1905, 1916) Quantum Mechanics (1920s?.) Nuclear fision (atom bomb, nuclear power), fusion (hydrogen bomb, Sun) (1940s?.) Transistors, semiconductors, superconductors (1940s?.) Big Bang theory, cosmic microwave background (1960s?) Quarks, Standard Model of Particle Physics(1960s?.) Dark Mater, Dark Energy?.(190s?.) 190019201940196019802000 1910, 18th edition of Ganot. 1928, 1938 Milikan et al. 1949 Sears & Zemansky 1960 Haliday & Resnick (from 197) 204 H&R/Cumings 204 S&Z/Young Milestones from the last century of physics education: What is MODERN MECHANICS? We will explain an enormous range of physics with just a very few fundamental principles. Matter can be described in terms of atoms that interact with each other (not just billiard ball physics). We will learn to create simple models for complex situations. We will use powerful computer graphics to simulate real physical behavior. We will show how mechanics plus real atomic behavior leads to thermodynamics: Mechanics ? Temperature! We will explain an enormous range of physics with just a very few fundamental principles. Matter can be described in terms of atoms that interact with each other. For those of you who brought your iClicker with you today, let?s do a test run: Turn the Power on. After the question is declared ?Open?, choose one: A.My last physics class was in high school. B.My last physics class was in college. C.I have never taken a physics class. D.None of the above. NOTE: From now on, always bring your iClicker to lecture with you. The quizzes count towards your grade. We will use powerful computer graphics to simulate real physical behavior. (Run VPython program for Moon Voyage, which students will write themselves during Lab #3. No prior programming experience needed!) from visual import * from __future__ import division G = 6.7e-11 #Universal gravitational constant day = 24*60*60 # seconds in a day pscale = 1 #momentum scale factor fscale = 40000 #force scale factor Earth=sphere(pos=vector(0,0,0), radius=6.4e6, color=color.cyan) Moon=sphere(pos=vector(4e8,0,0), radius=1.75e6, color=color.white) craft=sphere(pos=vector(-6.45e6,0,0), radius=1.e6, color=color.yellow) scene.center = vector(2e8,0,0) Earth.m = 6e24 # mass of Earth Earth.m=8.7061e+24 Moon.m = 7e22 # mass of Moon craft.m = 15e3 # mass of craft Earth.p=vector(0,0,0) Moon.p=vector(0,0,0) craft.v=vector(0,13336.,0) craft.p=craft.m*craft.v craft.trail = curve(color=craft.color) # for displaying the trajectory craftptheo=2.*craft.m/(1.-(6.45e6/4e8)**2)*G*Earth.m*craft.m*(1./(6.45e6)-1./(4e8)) print sqrt(craftptheo)/craft.m deltat = 2 # you should decrease this by half later to test if it is small enough t = 0 The initial parameters?. This stuff is ?overhead?, that sets the stage for the real calculations?. Some initial conditions & parameters?. Details?. Very important! while t < 32*day: r= craft.pos-Earth.pos # the relative position vector between the craft and the earth rmag= mag(r)# the magnitude of r rhat= r/rmag # the unit vector of r rmoon= craft.pos-Moon.pos # the relative position vector between the craft and the earth rmagmoon= mag(rmoon) # the magnitude of r rhatmoon= rmoon/rmagmoon # the unit vector of r Fmoon= -G*Moon.m*craft.m/rmagmoon/rmagmoon*rhatmoon Fearth= -G*Earth.m*craft.m/rmag/rmag*rhat# the force of the earth's gravity on the craft pold=craft.p craft.p= craft.p+(Fearth+Fmoon)*deltat # update the momentum craft.pos= craft.pos + craft.p/craft.m*deltat # update the position t=t+deltat craft.trail.append(pos=craft.pos) #appends new position to trail if rmag <= Earth.radius: # breaks out of the loop if the craft hits earth print "crashed" break if rmagmoon <= Moon.radius: # breaks out of the loop if the craft hits moon print "hit moon" print mag2(craft.p)/2/craft.m break print rmag The ?loop? that is running?. We will show how mechanics plus real atomic behavior leads to thermodynamics: Mechanical forces + quantized atomic energy levels + counting statistics = Thermodynamics/Entropy/Temperature Important Details: Reading Assignment: read Ch 1, sections 1-4 for today, sections 5-11 for Thursday. Go to your assigned Recitation this week. Turn in the first WebAssign HW by Thursday night. Do the first Lab on WebAssign by Tuesday of next week. Register your clicker in CHIP. John Peterson Lect01.ppt
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