# Exam 5 - 7'5” 6"\r EF 152 — Fall 2006 — Exam 5...

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Unformatted text preview: 7'5”) 6": /: \r/ EF 152 — Fall 2006 — Exam 5, Page 1 OfS Name: L’) Section: Exam Overview: a) The exam consists of 8 questions worth 12 points each (you get 4 points for correctly identifying your section number (A1, A2, B1, B2, C1,) b) Show all of your work c) Include units for all answers that require units d) Include the correct number of signiﬁcant digits e) Write your ﬁnal answer in the space provided Hints at) Stay calm b) Glance over all problems, tackle the “easy” ones first c) Use reasonableness to guide you (1) Allow yourself an average of 6 minutes per problem (12 minutes per page) R Units 1.987 Btu/(lb mole - R) 1.987 cal/(g mole - K) ‘ 0.730 atrn - ft3/(lb mole - R) 10.73 psia - ft3/(lb mole - R) 1545.0 (lb/ft?) - ft3/(1b mole - R) 1.314 atm - ft3/(lb mole - K) 82.06 atrn - cm3/(g mole - K) 0.082 L ' atm/(g mole ' K) 0.083 L - bar/(g mole . K) 8.31 J/[g mole - K) Molecular weight of oxygen is 32 Cp of water is 1.0 cal/(g K) Cp of aluminum 0.22 cal/(g K) (1 ofsteel 10.5 x 10'6 K'1 p ofwater is 1.0 g/cm3 P = RT/(V/n — b) — a(n/V)2 Figure lused for problem 8 EF 152 — Spring 2006 — Exam 5, Page 2 of5 Name: Section: 1. By how much will a steel rod of length 2.0 m and diameter 1.75 cm elongate if it is heated by 100 C A L -_- LoiAT ! AL : (9.0mm cox/5%“X/oo) .—. aim/m gar/mm 2. One Sunday morning a family takes an automobile trip to Grandma’s. At the start of the trip, the temperature is 288K (15°C), and the gauge pressure in the tires is 32 Ib/in2 (psi). (The gauge pressure is the excess over 14.5 psi, the exterior air pressure.) After an hour’s ride over an interstate highway, the gauge pressure in the tires is 38 psi. What is the temperature of the air in the tires, assuming that air behaves as an ideal gas? Neglect any changes in volume of the tires. EF 152 — Spring 2006 — Exam 5, Page 3 of5 Name: Section: 3.What is the Ideal Gas equation of state? What assumptions were used in its development and why is this equation of state so useful for engineering calculations? —L~ P 1/: WT I D/LOTE VaLWrE OF/baLéu/Lttj FLO 2,. L:an COLUSIa/Ve) M meta—"cam zi‘r‘wﬂcr/ga It W54 0F ML M5 Eve If 2. HEW/uth 6446 Cagﬁffgwa es ﬂ-ﬁgyLD‘r _ - 2; ﬂuiizuL F02? ﬂM W mmmwc Mar-s 4. What are state functions and why are they so useful for engineering calculations. Give two examples of state functions and explain what they are mathematically and physically. Powwow whim/1 £1191 m 19,147 SNAKE r ' / PH‘VSIC/ﬂu/T 719' ME Sir/9T 52%, 0F AIMS lo ﬁll/47700 pm, ﬂag CWT/fl“ gay/T W“? 6275166 mm in? “WE—l“ 537% 4 60/3/5955 M/ ﬂy; 4 OH} 1016/? m» lrW WWW [My ’9 WOW 0M. C0006“, )4 C040 " 145/0 FUMoTlc/nﬁ M? H4, Taﬂw ﬂHw/ﬂi ‘ TE b1 BECﬂfwag’ii/ue CW Wit/TE 7" 60“ one little“ 4%)!” Section: EF 152 7 Spring 2006 — Exam 5, Page 4 of 5 Name: 5. Explain the difference between a reversible and irreversible process, give an example and explain why reversible processes are so useful for designing processes and mechanical equipment. ~ 5 3 @m» AS 3 0 F041 4 ism-4941: //05 w i 7’ Wﬂﬂt’S‘5/é& (/F 4’ 4/” w 3 ' E WIN/M M C” 4 a: a - ﬂ . l3) IﬁﬂEUtﬂg/ﬂé ’0! Q— /_ 7—3137“ (in if - / .7- EY ﬂEFl/V Wﬂ/fr/r ﬂféy 6. How many kilojoules of energy are required to raise the temperature of a 3.0 kg bar of aluminum by 40K? EF 152 — Spring 2006 — Exam 5, Page 5 of5 Name: Section: 7. Your refrigerator can be thought of as a box with six sides of total area 2.5 m2. The effective R value of the walls is 1.5 m2 -K/W. The temperature inside is 5°C, while the temperature outside is 30°C. Calculate the rate of heat loss. 4 : .7 a N gamma) 3% R /.5' 2,54 2 Wm H Haw 8. Captain Schultz, the star high diver of the circus, insists that his bath always be exactly 37 C, body temperature, and measures the temperature of the bath with a precision thermometer before relaxing in it at the end of his day’s work. One terrible evening not so long ago the captain found his bath to be only 36.8 C. His noble countenance glowed with fury as he ordered his trembling valet to move his portable 80 kg tub from his private dressing tent to the foot of the high dive ladder. For a moment he paused, deep in thought, and then, ignoring the murmurs of the gathering crowd, he mounted the vertical ladder, counting the rungs as he climbed. He stopped at what was obviously a critical height. Disdainfully he let his dressing gown fall to the spellbound throng far below, and launched himself into the air, landing in his tub with such infinite precision that nary a drop of water was lost from the tiny splash. A smile lighted his features as he relaxed in his 37 C tub, while his valet quickly wheeled him back into his tent. Captain Schultz is 170 cm tall, has blond hair, weighs 70 kg. How high did he climb? Please see Figure I. m 90 AT ‘5: (gia’fﬂébo --—..~ (70 #Q/ffriXM) at: 925nm ...
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