HW6 Fall09

# HW6 Fall09 - PHY 317K HOMEWORK 6 DUE on December 2 2009 by...

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PHY 317K HOMEWORK # 6 DUE on December 2, 2009 by 8:00pm Instructions: Use a UT ANSWER SHEET to mark answers. Provide your NAME (last, first), UTEID , and UNIQUE NUMBER of the course. Sign and date it. The answer sheets must be placed in the 317K box located outside PAI 2.48. Late homework will not be graded . Answer the following 45 questions: 1. When the temperature of a copper penny is increased by 100 C ° , its diameter increases by 0.17%. The area of one of its faces increases by: A) 0.17% B) 0.34% C) 0.51% D) 0.13% E) 0.27% 2. The coefficient of linear expansion of iron is 1.1 × 10 –5 per C ° . The volume of an iron cube, 4.00 cm on each edge, will increase by what amount if it is heated from 15 ° C to 72 ° C? A) 0.01 cm 3 B) 0.07 cm 3 C) 0.12 cm 3 D) 0.23 cm 3 E) none of these 3. The heat capacity at constant volume and the heat capacity at constant pressure have different values because: A) heat increases the internal energy at constant volume but not at constant pressure B) heat increases the internal energy at constant pressure but not at constant volume C) the system does work at constant volume but not at constant pressure D) the system does work at constant pressure but not at constant volume E) the system does more work at constant volume than at constant pressure Page 1

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4. Solid A, with mass M , is at its melting point T A . It is placed in thermal contact with solid B, with heat capacity C B and initially at temperature T B B B ( T B > T B A ). The combination is thermally isolated. A has latent heat of fusion L and when it has melted has heat capacity C A . If A completely melts, the final temperature of both A and B is: A) ( C A T A + C B T B B B ML )/( C A + C B ) B B) ( C A T A C B T B B B + ML )/( C A + C B ) B C) ( C A T A C B T B B B ML )/( C A + C B ) B D) ( C A T A + C B T B B B + ML )/( C A + C B ) B E) ( C A T A + C B T B B B + ML )/( C A C B ) B 5. During the time that latent heat is involved in a change of state: A) the temperature does not change B) the substance always expands C) a chemical reaction takes place D) molecular activity remains constant E) kinetic energy changes into potential energy 6. Ten grams of ice at –20 ° C is to be changed to steam at 160 ° C. The specific heat of both ice and steam is 0.5 cal/g C ° . The heat of fusion is 80 cal/g and the heat of vaporization is 540 cal/g. The entire process requires: A) 1250 cal B) 5100 cal C) 6900 cal D) 7350 cal E) 7600 cal 7. A certain humidifier operates by raising water to the boiling point and then evaporating it. Every minute 15 g of water at 20 ° C are added to replace the 15 g that are evaporated. The heat of fusion of water is 333 kJ/kg, the heat of vaporization is 2256 kJ/kg, and the specific heat is 4190 J/kg ⋅Κ. How many joules of energy per minute does this humidifier require? A) 4800 B) 78,000 C) 39,000 D) 24,000 E) 2400 Page 2
8. According to the first law of thermodynamics, applied to a gas, the increase in the internal energy during any process: A) equals the heat input minus the work done on the gas B) equals the heat input plus the work done on the gas C) equals the work done on the gas minus the heat input D) is independent of the heat input

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HW6 Fall09 - PHY 317K HOMEWORK 6 DUE on December 2 2009 by...

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