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lecture_questions_final

# lecture_questions_final - On a cold winter day with T=-10 C...

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1 On a cold winter day with T=-10 ° C , the Eiffel Tower is 300 m tall. How tall is it on a hot summer day when T=40 ° C ? The Eiffel Tower is made from steel with a thermal expansion coefficient α =11 × 10 -6 /K . A. 300.001 m B. 300.16 m C. 316 m D. 420 m A cylindrical rod is just slightly too large to fit through a circular hole . If you want the rod to fit through the hole, should you heat the plate or cool it ? A. Heat B. Cool Suppose that it takes an amount of heat Q to bring a pot of water initially at 20 ° C to a boil. How much additional heat must you add to boil all water away? c = specific heat of water L v = latent heat of vaporization Additional heat = A. Q × L v B. Q × L v / c C. Q × L v / (c × 80 ° ) D. Q × L v / (c × 100 ° ) Suppose that it takes 10 minutes to bring a pot of water initially at 20 ° C to a boil. How much longer does it take to boil all the water away, assuming a constant rate of heat input? c=4190 J/(kg K) Lv=2256 kJ/kg A. 10 minutes B. 10 × (2256 × 10 3 ) / 4190 = 5400 minutes C. 10 × (2256 × 10 3 ) / (4190 × 80) = 67 minutes D. 10 × (2256 × 10 3 ) / (4190 × 100) = 54 minutes

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2 A copper pot containing boiling water sits on a hot stove element. The temperature of the water is 100 ° C. The bottom of the pot has an area of 0.04 m 2 and a thickness of 4 x 10 -3 m. k for copper is 400 W/(m K). If the stove element outputs 4000 W of heat to the pot, what is the temperature difference T across the copper bottom of the pot? T = ? A. 0.1 ° C B. 1 ° C C. 10 ° C D. 100 ° C E. 400 ° C k g /L g for a single-pane window with 1/8" thick glass is 25 times larger than k w /L w for a fiberglass-insulated exterior wall with a thickness of 6". What area of wall will conduct the same amount of heat from the inside to the outside of a house as a 4 m 2 window? A = ? A. 0.1 m 2 B. 1 m 2 C. 10 m 2 D. 100 m 2 E. 1000 m 2 An object with a temperature T o (in K) is placed in the middle of a large container whose walls are at T w = 0 K. If you double the temperature T o of the object, by what multiplicative factor does the net power that the object radiates to its environment change? P(2T)/P(T)=? A. 2 B. 4 C. 8 D. 16 E. 32 An object with a temperature T o,i (in K) is placed in the middle of a large container whose walls are at T w = 0 K. As the object cools by radiation, at what temperature T o will the net power it radiates be half its value at T o,i ? T o /T o,i = A. 1 B. (1/2) 1/4 = 0.84 C. (1/2) 1/2 = 0.71 D. 1/2
3 An object with a temperature T o (in K) is placed in the middle of a large container whose walls are at T w,i = 0 K. If you raise the temperature of the walls to T w =T o /2 , by what multiplicative factor does the net power that the object radiates to its environment change? A. 1/16 B. 1/4 C. 1/2 D. 15/16 E. 1 An object with a temperature T o (in K) is placed in the middle of a large container whose walls are at T w = 0 K. If you double the temperature T o of the object, by what multiplicative factor does the net power that the object radiates to its environment change?

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lecture_questions_final - On a cold winter day with T=-10 C...

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