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Unformatted text preview: irshad (si2865) HW10 distler (57205) 1 This printout should have 14 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. A somewhat shorter homework for this week... 001 10.0 points A copper telephone wire has essentially no sag between poles 39 m apart on a winter day when the temperature is 17 C. How much longer is the wire on a summer day when the temperature is 33 C? As sume that the thermal coefficient of copper is constant throughout this range at its room temperature value of 1 . 7 10 5 ( C) 1 . Correct answer: 3 . 315 cm. Explanation: Let : T = 17 C , L = 39 m , T 1 = 33 C , and = 1 . 7 10 5 ( C) 1 . The relation between length and tempera ture is L = L 1 L = L ( T 1 T ) , = (39 m) bracketleftbig 1 . 7 10 5 ( C) 1 bracketrightbig [33 C ( 17 C)] parenleftbigg 100 cm 1 m parenrightbigg = 3 . 315 cm . 002 (part 1 of 2) 10.0 points An air bubble originating from an under water diver has a radius of 9 . 8 mm at some depth h . When the bubble reaches the surface of the water, it has a radius of 7 mm. Assuming the temperature of the air in the bubble remains constant, determine the abso lute pressure at this depth h . The acceleration of gravity is 9 . 8 m / s 2 . Correct answer: 2 . 77144 10 5 Pa. Explanation: Let : = 1000 kg / m 3 , g = 9 . 8 m / s 2 , P atm = 1 . 01 10 5 Pa , R 1 = 7 mm = 0 . 007 m , and R 2 = 9 . 8 mm = 0 . 0098 m . From the ideal gas law P V = nRT = constant , so P 1 V 1 = P atm V atm P 1 P atm = V atm V 1 P 1 P atm = 4 3 R 3 2 4 3 R 3 1 P 1 = P atm R 3 2 R 3 1 = (1 . 01 10 5 Pa) (0 . 0098 m) 3 (0 . 007 m) 3 = 2 . 77144 10 5 Pa . 003 (part 2 of 2) 10.0 points Determine the depth of the diver. Correct answer: 17 . 9739 m. Explanation: The absolute pressure is P 1 = P atm + g h h = P 1 P atm g = 2 . 77144 10 5 Pa 1 . 01 10 5 Pa (1000 kg / m 3 ) (9 . 8 m / s 2 ) = 17 . 9739 m ....
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 Spring '08
 wandelt
 Chemistry, pH

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