Our Class Norms Physics 4810 7810 Week 11 zoinks Day 20 Fa2008 Politics Society and Physics Rotatitonal Motion and Rigid Body 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 Eyes to web Project DRAFT due in two weeks Draft can be various levels of finished more you provide me more response you get Debate Dissent and Discussion are patriotic Silent Lie What is the silent lie for Mediation Tools mediate allow for thought thought Fish Mahajan Bartlett Physics PER What are their stated goals Students How would BARTLETT MAHAJAN FISH change physics WHAT GOES HERE Students Goal Action Context Context is the collection of components and the relations among them the connected whole which includes constituent elements and the relations among them Birdwhistell uses the analogy of a rope to develop such a notion of context WHAT GOAL DOES IT SUPPORT 1 Context as Rope The fibers that make up the rope are discontinuous when you twist them together you don t make them continuous you make the thread continuous even though it may look in a thread as though each of those particles fibres are going all through it that isn t the case Obviously I am not talking about the environment I am not talking about inside and outside I am talking about the conditions of the system Birdwhistell as quoted in R McDermott 1993 p 274 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 treadmill 1 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 Practice this I leave my house lights on over night how much money did I waste hint you pay approx 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 s about 8 cents No big deal Does this mean energy is cheap Exponential growth Al Bartlett contends The greatest shortcoming of the human race is our inability to understand the exponential function Orders of Magnitude Exponential Growth Why OoM problems What can students instructors learn 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 to be to take advantage of avoid quantum tunneling 2 Estimation Orders of Magnitude Simple growth interest vs compounded Every year I ll give you 15 simple interest on your 1000 of principle 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 e rt where r interest rate 0 15 t time t 50 years r t 7 5 ert 1808 P 50yrs 1000 ert 1 800 000 Useful if you don t have exact data Too complex a calculation simplify formula Gives trends Solved by a simple equation OoM problems P t Po e rt t time 1yr r growth rate 0 05 yr What makes an OoM problem physics Time to double ie When is P t Po 2 ln P t Po Ln 2 ln ert rt 0 69 r x t Rule of 70 70 percent rate t time to double Share with each other your OoM problems What makes a good problem e g 3 growth year 27 years to double a 7 50 hamburger costs 30 in 54 years If it were 6 doubling time 70 6 13 years a 7 50 hamburger costs 120 in 52 years Can an OoM problem be political but apartisan A graphical example Population example Bacteria in a bottle Bacteria divide once every minute Start at 11AM At 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 bottles at 11 55 They find 3 new bottles Quadrupling all known space for bacteria How much more time did they buy themselves 3 Real world example Is this an issue Let us look at some current approximate data 1997 United States World Population 270 million 5700 million Annual increase 3 million 90 million Annual growth rate 1 per year 1 6 per year 70 years seems like a while Are we sustainable right now Think about food and non renewable energy for example What s the doubling time Energy Environment Phys 3070 http www colorado edu physics phys3070 Loads of data at www eia doe gov energy information administration How much energy do we use on what coa l gas oil domestic 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 renew oil foreign 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 is petroleum History of Oil Use What about US oil 35 30 History of Oil Extraction in world Sketch on a piece of 03 DOE EIA 29E9 bbl yr paper what happens here 03 DOE EIA 2 1E9 bbl yr 4 What does this mean U S Oil Curves Of course this is an estimate and perhaps worst case what is best case How does the US use energy What is inevitable 30 000 Gross Domestic Product GDP per capita Switzerland Sweden Japan Iceland 20 000 Norway Canada Germany Italy United States U K Belgium 10 000 Many countries in the world lie in this quarter circle India 0 0 Poland Cuba Ecuador 10 20 30 40 50 60 Energy equivalent barrels of oil per capita per year 5