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Physics 103 - Mechanics

Physics 103 - Mechanics. Pu'uhonua o Honaunau National Historical Park         Captain Cook, HI, June2009 Nat Hager III Masters 173 nehager@msi-sensing.com. F b. τ b. F w. τ w. Today’s Agenda. Introductions Syllabus Physics History

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Physics 103 - Mechanics

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  1. Physics 103 - Mechanics Pu'uhonua o Honaunau National Historical Park         Captain Cook, HI, June2009 Nat Hager III Masters 173 nehager@msi-sensing.com Fb τb Fw τw

  2. Today’s Agenda • Introductions • Syllabus • Physics History • Uncertainty, Scientific Notation • Fundamental Units • Unit Conversions • Estimating

  3. Introduction • Roster • Your background • MCATS • Camera shot • My Background • Industrial R&D • Aerospace SBIR • Concrete SBIR, NSF, Keystone Innovation.

  4. Syllabus • Lab, email, phone • Class times, places • Labs • Tentative schedule • Homework • Exams • Grading • Calculus

  5. A few thousand years ago. (skip) • Ancients wonder why: • Why does apple fall? • Why does moon go around earth? • Why does sun tides go up and go down? • (same law plus math of circles explains all!) • Never got to: • How do chemicals combine? (chemistry) • How does sun’s heat reach earth? (E&M) • How to living creatures function? (biology)

  6. How did Polynesians get to Hawaii? • Canoe floats as ΣF = 0 • But it can still rotate (capsize) in rough Pacific! • Outrigger provides moment arm and torque: Σт = 0 Fb τb Fw τw

  7. Development of Science • “Natural Philosophy” (Science) branched out, Physics retained core. • Relatively exact problems, depend heavily on mathematical reasoning. • Compliments your other courses (biology, chemistry, etc) “Natural Philosophy” Science (Physics) Chemistry Biology Geology, etc

  8. Physical Methods • Physics tries to provide “model” • Start with intuition and observation • Develop mathematically consistent model • Discard if contradiction • Refine model to resolve contradiction • Test of time.

  9. Development of models • Earth center of universe • Couldn’t explain planet motions • Absolute Time and Space • Couldn’t explain constancy of “c” • Mechanical Atoms • Couldn’t explain discrete energies

  10. Physics Today • Classical Physics • Mechanics • Electromagnetism • Thermodynamics • Acoustics • Optics • Modern Physics (things broke down 1900-1920) • Relativity • Quantum Mechanics

  11. Uncertainty and Scientific Notation • Every measurement has uncertainty • Ruler, volume, weight, voltmeter, etc • Percent uncertainty • Sig Figs • Do NOT specify sig figs > uncertainty • Retain sig figs for intermediate calculation • Round sensibly final answer (297.335 mL ???) • Don’t do “calculator dump” • Scientific Notation • 6.02 x 1023 • 6.67 x 10-11 N m2/kg2

  12. Fundamental Units • Length (meter) • 1/10000 distance earth to equator. • Later def. platinum bar. • Later def. distance light travels in 1/299,792,458 sec • Kilometer (numbers 1.6 larger) • Everyday millimeters • Mass (kilogram) • Mass in French vault • Approximate 1 Liter water • Prefixed unit is base. • Trend to redefine • Second (time) • 1/86400 of solar day • Cesium atom standard • Always use meter/kilogram/second as base units!

  13. SI Prefixes • Tera (1e12) • Giga (1e9) hard drives (approx) • Mega (1e6) RAM (approx) • Kilo (1e3) kilometer – 1/2 times bigger • Hecto (1e2) • Dek1 ( 1e1) • Base unit Meter (show) • Deci (1e-1) • Centi (1e-2) centimeter (show) • Milli (1e-3) millimeter (handout “everyday millimeters”) • Micro (1e-6) microchip • Nano (1e-9) nanotechnology • Pico (1-12) picofard • Kilogram, not gram is base unit for mass (slightly inconsistent)

  14. Dimensional Analysis • Converting units • Inch >> cm • (1 inch)(2.54 cm/inch) = 2.54 cm • Mile >> km • Hour >> second • (1 h)(60 min/h)(60 s/min) = 3600 s • km/h >> m/s • (90 km/h)(1000 m/km)(1h/60min)(1min/60s) = 25 m/s • Note: * (60min/1h) is wrong dimensionally! • (Km/h 3.6 = m/s)

  15. Dimensional Analysis • Performing calculations • Velocity is always distance/time • Distance = velocity * time • (Using formula for constant velocity)

  16. Estimating • How much mulch do I need for backyard? • Side yard ~12 m • Front of house ~6 m1 • Heat pump ~1 m • Garage ~ 1 m • All about 1.5 m wide = 30 m2 • Make 100 mm deep • 30 m2 * 0.1 m = 3 m3 (4 yd2 from mulch store)

  17. How big was oil spill? • The Deepwater Horizon oil spill added roughly 800 million liters of hydrocarbons to the Gulf of Mexico. One quarter of that has been burned, captured or skimmed, according to U.S. government estimates. That leaves the rest for trillions of microbes to feast on—a petroleum cornucopia that first became available April 20 when the oil platform exploded and the spill started. • 800 million liters = 800,000,000 liters = 800,000 m3 • Method 1 (Family house size) • My house size 7.9 x 12.7 m = 100 m2 McMansion size 200 m2 • Height 5 m (2 floors + attic) • Volume 200 m2 x 5 m = 1000 m3 • 800,000 / 1000 = 800 family houses • Method 2 (Master’s Center) • Esbenshade Hall is about 45 m long • Let’s take Master’s as approximately square 50 m x 50 m • Height (2.5 m ceiling, 3 m floors, x3 floors ) 10 m • Volume 50 x 50 x 10 = 25,000 m3 • 800,000 / 25,000 = 32 Master’s Centers *http://www.scientificamerican.com/article.cfm?id=gulf-oil-eating-microbes-slide-show

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