Fa06-MT1-Packard-Soln

Fa06-MT1-Packard-Soln - Physics 7b Fall 2006 Midterm 1 R....

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Unformatted text preview: Physics 7b Fall 2006 Midterm 1 R. Packard Work all problems. Introduce and clearly define algebraic symbols to represent a_ll physical quantities. Do not perform numerical work until you have a final algebraic answer within a box. Check the dimensions of your answer before inserting numbers. Work the easiest parts first, and the next hardest, etc. If you do not understand the question ask the proctor for assistance. All problems are weighted equally. kB=1 .38x10'23J/K, NA=6.02x1023, latent heat of fusion of water 3.3x105J/kg, specific heat of ice, 2100J/kgC°, specific heat of liquid water 4186J/kgC0, o=5.6x10'8W/m2K4 When considering gas processes you may assume the gas follows the ideal gas law. Name - S O [Milion S SID Sect. # or day and time TA name (if known) Problems 1,2, and 3 all are based on the same “house” described in problem 1. - 10m/’ 10m L’v é—L: *9 K 1'. Consider a house with a square “footprint” (i.e. base) 10m on each side and height 5m. Air is ~80% N2 with a molecular weight Mw=28g/mole a. (Spts) Estimate how many air molecules fill the interior space of the house when the inside temperature is 20°C. Tell what assumptions you made for the estimate. b. (Spts) The walls of the house have a linear expansion coefficient 0L=1x10'5/°C. If the temperature of the walls changes by 10°C, what is the fractional change in the interior volume? c. (5pts) Assuming that the house is not air tight, what is the fractional change in the number density of molecules (i.e. number per unit volume) corresponding to this 10°C temperature rise? a) 0\§6‘V\w\€ Pressme 13 QA‘ lat/hm '2 LOB X10“S Fa According) 2(2) fatech INN ?V= NKT : 1w LOGXIOSX (5)0 H) I ’ i [N E? __ _____________°_°_ : 10,5;me waxwfi x (273m) [9) Fm knee/1r exfmsfm , 4L: otLoAT 41., = lxm‘5x10xlo :1 (0‘3 m $1.2, = ALi = (0”3 W‘ 4L3 1 lxto“5XSXlo 2 5x(0”4’*v~ firm“ WWW : Vf = (M71153) xtlo+to~3lx(5+ 5x54) rm? (Here I aswmg Hue fiwfermwe fixes (0°C, gm Can also Axum (\hfh‘ag. Volume : v0 ~ [oxioxs m3 3‘: Vf'Vo _. V0 : V0 3 Eng 4 HQ WM drafDS got.) O R F01 Vomm axFahSRm [3 r: 3 (X A ~ _ E "2 [54‘7- = 3n€5xm 0) Wham/t- lnah‘a/Lba rP V0 ‘: N C To Ian ? Vg. 1 K if 1!; -31 ‘ 1 ‘- V0 .— [(TD £10 ‘ ‘ P V0 kTo _ ‘ I ‘ a ([3 ( aqaw 0 No ‘1’ => => 51-3. V{-' KT; v.L . 1TU('T£."+;) ,_‘_ 9&3) S.‘w+ka kmgq {5 not om‘r twig, flu; FMupy-e A!“ H43 cht, tL‘Q mwfgwdim-‘Q YfS£5 ‘OVk ( WHOM F3 deny/7)) 20‘} / I V H I 1 /VI rad/I73 7th“: 7/vna/7f/V’afhuf of a juhw‘mflin) head bl’qu/ygd W (H M a we 1%va ~"./'.5‘4( m/ wl @7HCAT (07/ VACAT}. {7746 U01 (ME 0% 61/87) 691651.: 07"? "J’é'f V‘fZJCE 3' {a} V6} are Ma +€mljera+1flflf , 6V6 arr: filu/O g1” c/u /.// Afl aFC/ér-jflfr’l’gd ’7 (0W57LZ4M{” (/OKuVrUZ (bkflwu‘fiem Unm¥€d by ah/MV of AW‘“ 1‘7" “3‘17”! 9”) 01’ CMSva/nf’ @VC’J‘SOVC {bywwge' aux WV?“ V3 {1% be C(ng 71734445. , 14:1,”.1 {Jifffu : r5” [‘3‘ 0Q WWI'y’lfL/r( ’35 5-" ’Jf'V 0" pin." 4‘! ’ C,.J715+zloi'{ V0 W "La 2 (13” g-Jv-am + E 1’, (‘7 ” Q’V%AT ,- ,A/ Q'Wgcule 7 2 : D +1. Cu 2 R ‘ ~ Cp ’2 72 assum dl'afo’mt'c (arr v9 rmosJ'h/ A] ’D ; 6’ 3 ’13 p 3— > Q ; ZL , I X/OM» “fag-1M4wj‘5 K -' D _ W W" ' ‘ 2; I Q ’ A/ a EQ/A/A ’AT 1/, 2 ,0! x/U ( 7K} (1 Qiq4>m1iJIN§ , 5 / ’ ' /' ng/O'ZST ' “ ‘ I, _‘ W 2 TI [5“ Pom/Lax is dr/é‘flfi " > {4W1 : [0-2, T Q(a\ p 3 31k 3 ’ /’ ‘ l J :IW'S = /0'3ka) o3 4', _. A t - Q/a". ,— 2: X/0'7 “EA/’1’”, Wh‘m'H-Mw H “m ” u ‘ ~ u '7 M ‘ \ /fl_fl_wm>u~myw‘ vm‘kmw-w “I-” Q : 7.44x/O'18’kwhr,A/; imsk you 22 (fl ‘N -—~——w-—~.-m-—M__.i At 3 I' (Nix/01’ kw ' {#00 pNSSuw/t? 1 F] \ 2A it know {442. rod-e. been} News ooi~ ef- +b: gee.” it». We, summer. We. use, “we. rad-e iwi-LL wind-u- i'o wive, for i-Lo. reievawi' cambth (a? variokles . . wt 3. (15pts) This house requires SkW of heat on a winter day when it is i 13°C outside and 219C inside. In the summer this house is cooled by an air conditioner (a refrigerator unit which cools the inside, pumping the heat to the outside) which operates at 75% of the Carnot coefficient of performance for a refrigerator. When it is 37° outside, how much does it cost to cool the house for one month if the inside temperature remains at 21°C inside and if the cost of electricity is $0.14/kWhr. Assume the inside and outside temperatures remain co -%E:9hsw=fim“9- «. 4. (15pts) A metal ball of radius 1m is heated to a temperature of 800°C. The ball is placed near a curved mirror so that 20% of the emitted thermal radiation falls onto a small box containing 5kg of ice at -10°C. Assuming the ball’s emissivity is s=0.6 and the absorptivity of the box is 1, how long does it take to melt the ice and raise the water within to +20°C? ’ W w W” u” rover m '4 L7 b‘* Lea-53¢, I‘J’ :5 "Ii; {:1 Wu, $525)” #1.. an 0“ ‘Pm rover L7 A“. srhm, (fly-l 1,00% first, we (“.4 MM, Lu W thi‘od L, 11“ SW: E; e‘Ap-Efl , lLe swim arm 01 «graham, :s ’1er PM rs «0 almwmwo P= 4;"; , il.t.1\ A.“ not at,” mm, to P=f—§— 4% Nu): m to 1L. PM, “Liam £711.. 5.“ an = éb (1&3) = M3 Bazagtzufi’f‘lmbflfi “If. (.M‘imi) a; Lox warm, We”; and “no. war" m, (an “It heal (“VIM-F‘J {.r £041 0" “use “‘73 Mama...” " "Mac Na». AQ Re. luau-5 3 Male. Lt“, . , AQqu'o'Unnnv 1 My” (we, no.1 mm” anyhlr ’ “:5 “nu, 3W 5. A4“? 3 "Ira. Che. 67:2,, + “9:5. Lu I'M i“.ka a. m (Lac ATE“— + LI“ *CVJT Armhr) 4L} {6 a in sulfa. Lu- + ‘Al Fit" 2‘) $0 +‘é-g-i'32 IF. z,|oo%3¢'l0.(, “340,2 +4186’1.u‘5) . " .z-M (5.540%,0 (ml‘XRoszMTI mm: ; 5. (15pts) (Prob. 20—39 from homework) What is the total change in entropy when 2.5 kg of water at 0°C is frozen to ice at 0°C by being in contact with 450 kg of ice at -15°C? ASHM wakr untiergaes « 3M5: ‘i'Tansi-h'dn’ w~gr val +q+k keai' QLSOYLCJ 44,4, km} 1i- cA‘MtSu-P :5 Nb LVI W a'F 3((. “a Yer HM. wed": T=ZJ3K Aswan!" “9—- Twp. :1 .a mum L .pgsum Tun i" Hm Sign is ('3 beau“: km} tum-35 atria 3 So 55 z s - 5k (3.9105 5/ 3) 43.3.0sz!) 37K z’flK For HM. NC /A 5* “bSorbeci cams H-a Hmfeml-ww ) ‘MC-Toro T4: “oh. g f MECTO MC.T3 m9“). “.5. nu, 5 Q ‘MmeMM = (LSerXS3XJOSS/K3) 9.25% g s mc= Q50 k3 (poo Y/ks‘d 1.45m! 7/K 50 T4,: 259.8}K . ounfic‘ H‘ afievnt-l- make Muck dI-F-Fercnte 1(— we ugg L53, wtgy.?K. So JVS'W‘S 157'“ K (Tu avg'ma‘ Weflhn)‘ 48'.“ zmuum L-Magg .: . , Tag “as ASTOTAL: A Swukr‘tbsiu 3' {‘40 5/K | ...
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This note was uploaded on 09/09/2008 for the course PHYSICS 7B taught by Professor Packard during the Fall '08 term at Berkeley.

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Fa06-MT1-Packard-Soln - Physics 7b Fall 2006 Midterm 1 R....

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