news_051711

news_051711 - p 2 m/s 2 = 2 m/s = 1.4 m/s T1, T2 and T3...

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Stuff for Tuesday, May 17, 2011 1094 session on Wednesday. Read T3 in advance. Quiz on Friday on T1, T2, and T3. Recap on calculation of P = N V [ mv 2 x ] avg = N V k B T : Assumptions Corrections 1. N is huge It is huge! 10 23 is a typical number. 2. gas molecule ± avg. volume V V - b N N A “excluded volume” 3. molecules act like particles quantum mechanics! (critical at low T ) 4. no interactions between particles P P + a 0 ( N / V ) 2 5. all molecules in gas are identical P s = N s k B T for species s 6. all collisions with wall are elastic works on average (but complicated!) 7. motion of molecules is random good approx. but could simulate Consider 5 particles with v x = - 2 m/s, - 1 m/s, 0 m/s, 1 m/s, 2 m/s. average velocity: [ v x ] avg = 1 5 P 5 i = 1 v x i = 1 5 ( - 2 - 1 + 0 + 1 + 2 ) = 0 m/s average speed: [ | v x | ] avg = 1 5 ( 2 + 1 + 0 + 1 + 2 ) = 6 5 m/s = 1.2 m/s rms velocity: p [ v 2 x ] avg = q 1 5 ( 4 + 1 + 0 + 1 + 4 ) =
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Unformatted text preview: p 2 m/s 2 = 2 m/s = 1.4 m/s T1, T2 and T3 Stuff Specic heat c : dU = mc dT or c 1 m dU dT Ideal gas law: PV = Nk B T with k B = 1 . 38 10-23 J/K Temperature and energy: K avg = 1 2 [ mv 2 ] avg = 3 2 k B T = v rms q [ v 2 ] avg = r 3 k B T m Thermal energy of a gas: U = f 2 Nk B T Near room T , f 3 (monatomic gas), f 5 (diatomic gas), and f > 6 (polyatomic gas) f is called the number of molecular degrees of freedom Gas processes: heat is energy ow from T First Law: U = Q + W Expansion or compression work: dW =-P dV Adiabatic: TV -1 = const. PV = const. = 1 + 2 / f...
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This note was uploaded on 06/03/2011 for the course H 133 taught by Professor Furnstahl during the Spring '11 term at Ohio State.

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news_051711 - p 2 m/s 2 = 2 m/s = 1.4 m/s T1, T2 and T3...

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