7aCDW11quiz8

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Phy7A Quiz8 DL Sec ____ Name ( last ) ___________________ ( first ) ____________________ I certify by my signature that I will abide by the code of academic conduct of the University of California. Signature ________________________________________ Physics 7A Quiz 8 Winter 2011 1 Rubric Codes: No books or notes. Calculators OK. Show all your work below. Answers alone do not receive credit! 1) The picture to the right shows two solid metal cylinders, one made of niobium (Nb) with a mass of 0.86 kg and one made of tantalum (Ta) with a mass of 1.67 kg. Ta atoms are much more massive than Nb atoms so these two cylinders have the same volume and the same number of atoms. a) Suppose you add an equal small amount of heat to each cylinder. Decide whether the niobium cylinder will increase its temperature more, the same, or less than the temperature increase of the tantalum cylinder?
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Unformatted text preview: Explain your answer completely including any assumptions that you make. b) Suppose the two cylinders are both sitting on the desk in this lecture hall. Are the Nb atoms moving faster, the same, or slower (on average) than the Ta atoms? Explain your answer completely including any assumptions that you make. 2) Now compare the Nb cylinder with a balloon that has 0.86 kg of He gas. He atoms have about 23 times smaller mass than Nb atoms. Again, suppose you add equal amounts of heat to the Nb and the He and decide whether the Nb will increase its temperature more, the same, or less than the temperature increase of the He? Explain your answer completely including any assumptions that you make. Useful equations and constants E th /mode = ½ k B T Δ U = Q + W R = 8.3 J/mole K C = Q/ Δ T E th /mode/mole = ½ RT C P = C V + nR k B = 1.4x10-23 J/K Nb Ta...
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