1Physics 4810 / 7810 Week 11 (zoinks!)Day 20: Fa2008:Politics, Society and PhysicsRotatitonal Motion and Rigid BodyEyes to webProject DRAFT due in two weeksDraft can be various levels of finished--- more you provide me, more response you getOur Class Norms…• Again, potentially charged topics• Please focus on ideas, not people• CONSTRUCTIVE critiques are the best• It is okay & encouraged for you to differ with:– Authors– Professor– And maybe each other…• Debate, Dissent, and Discussion are patriotic ; )Silent Lie• What is the silent lie for:– Fish– Mahajan– Bartlett• What are their stated goals???Mediation• Tools mediate (allow for thought) thoughtStudentsGoal / ActionPhysics / PERHow would BARTLETT/MAHAJAN/FISHchange physics?StudentsWHAT GOAL DOES IT SUPPORTWHAT GOES HERE?Context• Context is the collection of componentsand the relations among them - theconnected whole which includesconstituent elements and the relationsamong them.• Birdwhistell uses the analogy of a rope todevelop such a notion of context:2Context as RopeThe fibers that make up the rope arediscontinuous; when you twist them togetheryou don't make them continuous, you makethe thread continuous .... even though it maylook in a thread as though each of thoseparticles[fibres] are going all through it, thatisn't the case... Obviously, I am not talkingabout the environment. I am not talkingabout inside and outside. I am talking aboutthe conditions of the system(Birdwhistell as quoted in R. McDermott 1993, p. 274).Practice thisI leave my house lights on over night, howmuch money did I waste (hint: you payapprox. 10cents /(kW*hr) )?Energy = power*time = 100W * 8 hrs = 800 W*hr= 0.8 kW*hr.Since you pay about $0.10 for each kW*hr, that'sabout 8 cents. No big deal. Does this mean energy ischeap?More Practice• What if I have to produce this energy 0.8 kW*hrs?Assume I am about 1/10th of a horse 0.1 horsepower running on a treadmill1 hp = 750 Watts.So I produce about 75 Watts. For how long to get 800 Watt - hrs?(more than the amount of time I left the bulb on!)Is energy still cheap? [I’m willing to pay you 8 cents to do this]Exponential growth• Al Bartlett contends, "The greatestshortcoming of the human race is ourinability to understand the exponentialfunction."Orders of Magnitude /Exponential Growth• How much will a hamburger cost in 2052?• When will we run out of fossil fuels?• How long does it take to charge a flash?• How close do circuit components have tobe to take advantage of / avoid quantumtunneling?Why OoM problems?What can students / instructors learn???3Estimation / Orders of Magnitude• Useful if you don’t have exact data• Too complex a calculation -- simplifyformula• Gives trendsSimple growth (interest) vs.compounded.• Every year I’ll give you 15% simple interest on your $1000 ofprinciple investment..for the next 50 years• I.e. $150/year…. Or $7500• What if I got interest on the interest?– i.e. Year two, I get 0.15*$1150…• Or instantaneously!– P(t) = Po * ert where r = interest rate= 0.15, t=time– t = 50 years ---> r*t = 7.5 --> ert = 1808– P(50yrs) = $1000*ert = $1,800,000 !!!!!Solved by a simple equationP(t) = Po * ertt = time =1yr r=growth rate 0.05 / yrTime to double … ie. When is P(t)/Po = 2?ln(P(t)/Po) = Ln(2) = ln(ert)=rt0.69 = r x tRule of 70: 70/(percent rate) = t= time to doublee.g. 3 % growth/year => 27 years to doublea $7.50 hamburger costs $30 in ~54 years.If it were 6% -> doubling time = 70/6 = 13 yearsa $7.50 hamburger costs $120 in 52 yearsOoM problems• What makes an OoM problem physics?• Share with each other your OoM problems• What makes a good problem?• Can an OoM problem be political but apartisan???Population exampleBacteria in a bottleBacteria divide once every minuteStart at 11AMAt noon the bottle is filled• What time is it when the bottle 1/2 full?• What time is it when the bottle is 1/32 full?• Three adventurous bacteria are sent out to find new bottlesat 11:55. They find 3 new bottles!!! Quadrupling allknown space for bacteria.• How much more time did they buy themselves??A graphical example4Real-world example• Let us look at some current approximate, data (1997).United States WorldPopulation 270 million 5700 millionAnnual increase 3 million 90 millionAnnual growth rate 1 % per year 1.6 % per yearWhat’s the doubling time? ?Is this an issue?• 70 years seems like a while?• Are we sustainable right now?• Think about food and non-renewableenergy for example.Energy & Environment Phys 3070http://www.colorado.edu/physics/phys3070• Loads of data at:www.eia.doe.gov (energy information administration)• Global coal USE is about 100 QBtu/yr = 5E9 ton/year• Global coal reserves are estimated (high end est.) at 20,000 Qbtu• Global fossil fuel USE is about 400 QBtu/yr• Global oil reserves are estimated (high end est.) at 10,000 Qbtu• US coal USE is 20 QBtu/yr = 1E9 ton/year• US fossil fuel USE is about 100 QBtu (of which 40 ispetroleum)How much energy do we use?on what?coalgasoiloildomesticforeignrenew.History of Oil Use'03 DOE-EIA29E9 bbl/yrSketch on apiece ofpaper whathappens hereHistory of OilExtraction in world3035What about US oil?'03 DOE-EIA2.1E9 bbl/yr5U.S. Oil CurvesWhat does this mean?Of course this is an estimate (and perhaps worst case); what is bestcase?How does the US use energy?30,00020,00010,000010 20 30 40 50 600Energy equivalent barrels of oil per capita per yearGross Domestic Product (GDP): $ per capitaPolandCubaEcuadorIndiaItalyU.K.JapanSwitzerlandSwedenNorwayIcelandGermanyBelgiumCanadaUnited StatesMany countries in the world lie in this quarter-circle!!What is
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