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Quiz7_Solution

# Quiz7_Solution - Quiz 7 Monday March 30‘“ 2009 PHY 252...

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Unformatted text preview: Quiz 7. Monday, March 30‘“, 2009 PHY 252 \$01. UTIOIO Name: 1. In one cycle, an engine extracts 750. J of heat from a hot reservoir while doing 100. J of work. (a) What is the efﬁciency of the engine? (1 point) E = 'w’ : \$99 := 0.83 _=_ 133% -— ’1‘ | Q H I 150 (b) How much heat per cycle is exhausted to the cold reservoir? (1 point) Enter-33 is conserved, so 61” = QL + w QL : QH-W 7—" 3130-400 1 650:)” -—-—--—--——~-—* An ideal heat engine has a theoretical efﬁciency of 30.0 % when the high temperature reservoir is at TH = 227 °C. (c) What is the temperature of the low temperature reservoir, TL '2 (1 point) _ ‘I" ._ 2H“ -— I —- tr: _—_> 11—— C)—~£:)T.. H = ‘—' 0.3)):(5'00K = 350 K 7F 2. 1.00 kg of ice at 0.0 °C is thrown into a large lake of water whose temperature is 15.0 °C. Estimate the entropy change of the original water in the ice after it has come to equilibrium with the lake’s water. (LF = 333 Jig , cw = 4.190 J/g.C°) (2 points) Ice ﬁrst-Tmelts at T; = 0.02 (273K), then is. War-meal {=ng = 15°C (288k) & As 2 tic-g? = ML" + MCNALIQ T; "I"; H. a 239 =(Iooog)n(33321'lq) +(ioooa)(4.-HO 313,5 ) m 2.?3K :. I‘ZI‘IVK'TIK + 0.22.9—IKU'IK ::. [,LPLPK‘IIKHaé What is the entropy change of the ice + lake system? (2 points) The lake releases heat to flue ice at a conduit “WafelS‘c. (189K) ank9 = “area = “MLF "‘ MCw(T5-T;_) = - (meg) (333-513) ~Cjaooﬂ)x (tr-rqoq-h.c°) ( r:~o) =-_ - 35?. Ho‘ -. (2.851(3‘ = ~3‘lS-85KI as,er Qlake :__ —. 395-95: : __ ,_374 mm 1,. Take 288R Aslakc : iee Lake + AS;cc 2 —- 1.3?9-4 + 1.1.4.39 a 0.06‘1 luv/K 4(- Quiz 7. Monday, March 30“', 2009 PHY 252 3. A quantity of gas undergoes the cycle shown in the 500 B ﬁgure. If TC = 1000. K; 400 (a) How many moles of gas are there? (1 point) A PC VC, = “ RTG C lei-Cal. dQ‘S law ) Hg Adlabat P‘VL __ ClaoxwaAJJxCIS‘M3) a h = - —————————-—* v m; (3.3:zra‘m.l.k) 4,000 K) m 200 n : 180.11. Moles 7“ 100 (b) Estimate the speciﬁc heat at constant volume of the gas, and comment on your result. (2 points) 3c. la an adhaloat. QB¢=O Cluck 93v: V x :: £2. ..-=. X44 (4) R: > U ( Vs M4. X 2 ,Lu (PG/Pa.) 14(4‘SKM/lﬂokﬁ In“) in. (lie/V3,) IS/g) X -"—" l-3‘78cl 2 [.11- :2 5 2 E: '— CV +R : l 'l- .3. —- C CV CV CV j v . x :. Z-SR '-= g}; ——- 7V— Covuuext: AFPeM-S 15° be“ diatomic (c) What is the work done in the cycle? (3 bonus points) ﬂats ' Silage Qac '—"—O2 Ilt appear-.5: to be Slmpler ‘15- we couloqu Q :fl'rsl', a.ch iLeu LLSe W 2 61 {your- a. Cdclt'c process a: Q“ + 613‘ + a“ 2 nchra-T.) +0 +nCP(T&—T¢) We need TA _ TA 7:. To 1/}: CPCOMJéd-uf) TA, 2 :2. K -_.. v‘ 3 '5- We need. ‘3 TB 2 Tc Pat’s 2 “JOCK liésx‘o x 5- : [1550 K puavo Ioomo3 x IS' Q = (mo-swam) x 8-314—3lnal. x) ( lS‘SO ~333.3) + 080.4%) (3148-3149(333 - low) Q: 9-,5‘62 K: — 3,501K: : Local H: Sl'hce AE=O {-OI‘ acdcle w : Q : 1,06; KI Pasiblve for a Cdcll'c Process ...
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Quiz7_Solution - Quiz 7 Monday March 30‘“ 2009 PHY 252...

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