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Announcements

Announcements Physics lecture today 4 PM – Professor Brian Matthews from U. Oregon – “Tolerance and Intolerance in Protein Structure and Function” Third exam on Chaps. 15-20 – Tuesday, Nov. 25 th Bring: Equation sheet (8.5  x 11 ) Calculator Clear head Extra problem solving session ?

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Announcements

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  1. Announcements • Physics lecture today 4 PM – Professor Brian Matthews from U. Oregon – “Tolerance and Intolerance in Protein Structure and Function” • Third exam on Chaps. 15-20 – Tuesday, Nov. 25th • Bring: • Equation sheet (8.5 x 11) • Calculator • Clear head • Extra problem solving session ? • Sunday night 10-11 PM ? • Monday evening 6-7 PM ? • Other ? PHY 113 -- Lecture Review 15-20

  2. Advice for preparing for exam: • Review lecture notes and text chapters • Prepare equation sheet • Work problems using equation sheet and calculator • From homework • From previous exams • From on line quizes • Topics: • Simple harmonic motion & resonance • Wave motion, standing waves, sound waves • The physics of fluids • Thermodynamics & the ideal gas law PHY 113 -- Lecture Review 15-20

  3. Simple harmonic motion & resonance Hooke’s law: Simple pendulum: PHY 113 -- Lecture Review 15-20

  4. The notion of resonance: Suppose F=-kx+F0 sin(Wt) According to Newton’s second law: PHY 113 -- Lecture Review 15-20

  5. Physics of a “driven” harmonic oscillator: “driving” frequency “natural” frequency (mag) (W=2rad/s) w PHY 113 -- Lecture Review 15-20

  6. The phenomenon of wave motion • The wave equation position time PHY 113 -- Lecture Review 15-20

  7. The wave equation: Solutions: y(x,t) = f (x ± vt) function of any shape Moving “pulse”: Periodic wave: “wave vector” not spring constant!!! PHY 113 -- Lecture Review 15-20

  8. Superposition of waves: “Standing” wave: PHY 113 -- Lecture Review 15-20

  9. Constraints of standing waves: (  = 0 ) PHY 113 -- Lecture Review 15-20

  10. The sound of music String instruments (Guitar, violin, etc.)  Couples to sound in the air PHY 113 -- Lecture Review 15-20

  11. Sound waves • Longitudinal waves propagating in a fluid or solid PHY 113 -- Lecture Review 15-20

  12. Periodic sound wave In terms of pressure: Sound intensity: (energy/(unit time × unit area)) Decibel scale: PHY 113 -- Lecture Review 15-20

  13. “Wind” instruments (standing waves in air) PHY 113 -- Lecture Review 15-20

  14. toward away The “Doppler” effect v=sound velocity observer moving, source stationary observer source vS=0 d PHY 113 -- Lecture Review 15-20

  15. The physics of fluids. • Fluids include liquids (usually “incompressible) and gases (highly “compressible”). • Fluids obey Newton’s equations of motion, but because they move within their containers, the application of Newton’s laws to fluids introduces some new forms. • Pressure: P=force/area 1 (N/m2) = 1 Pascal • Density: r =mass/volume 1 kg/m3 = 0.001 gm/ml Note: In this chapter Ppressure (NOT MOMENTUM) PHY 113 -- Lecture Review 15-20

  16. Density: r =mass/volume Effects of the weight of a fluid: P(y+Dy) rgDy y P(y) Note: In this formulation +y is defined to be in the up direction. PHY 113 -- Lecture Review 15-20

  17. For an “incompressible” fluid (such as mercury): r = 13.585 x 103 kg/m3 (constant) Example: r = 13.595 x 103 kg/m3 PHY 113 -- Lecture Review 15-20

  18. Buoyant force for fluid acting on a solid: FB=rfluidVdisplacedg FB - mg = 0 rfluidVsubmergedg -rsolidVsolidg = 0 A Dy mg PHY 113 -- Lecture Review 15-20

  19. Bouyant forces: the tip of the iceburg Source:http://bb-bird.com/iceburg.html PHY 113 -- Lecture Review 15-20

  20. Effects of the weight of a “compressible” fluid on pressure. y-y0(mi) P (atm) PHY 113 -- Lecture Review 15-20

  21. Energetics of fluids: Dx1 =v1Dt Dx2 =v2Dt A1 Dx1= A2 Dx2 m = r A1 Dx1 K2 + U2 = K1 + U1 +W12 ½ mv22 + mgh2 = ½ mv12 + mgh1 + (P1 A1 Dx1– P2 A2 Dx2) P2 + ½ rv22 + rgh2 = P1 + ½ rv12 + rgh1 PHY 113 -- Lecture Review 15-20

  22. Bernoulli’s equation: P2 + ½ rv22 + rgh2 = P1 + ½ rv12 + rgh1 Example: Suppose we know A1, A2, r, P, y1, y2 P + ½ rv22 + rgy2 = P0 + ½ rv12 + rgy1 PHY 113 -- Lecture Review 15-20

  23. Thermodynamic statement of conservation of energy – First Law of Thermodynamics DEint = Q - W Work done by system Heat added to system “Internal” energy of system PHY 113 -- Lecture Review 15-20

  24. How is temperature related to Eint? Consider an ideal gas  Analytic expressions for physical variables  Approximates several real situations Ideal Gas Law: P V = n R T temperature (K) volume (m3) gas constant (8.31 J/(moleK)) pressure (Pa) number of moles PHY 113 -- Lecture Review 15-20

  25. Review of results from ideal gas analysis in terms of the specific heat ratio gº CP/CV: PHY 113 -- Lecture Review 15-20

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