ch18-p068

ch18-p068 - T B in the “y intercept” that is c B c A c...

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68. As is shown in the textbook for Sample Problem 18-4, we can express the final temperature in the following way: T f = m A c A T A + m B c B T B m A c A + m B c B = c A T A + c B T B c A + c B where the last equality is made possible by the fact that m A = m B . Thus, in a graph of T f versus T A , the “slope” must be c A /( c A + c B ), and the “y intercept” is c B /( c A + c B ) T B . From the observation that the “slope” is equal to 2/5 we can determine, then, not only the ratio of the heat capacities but also the coefficient of
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Unformatted text preview: T B in the “y intercept”; that is, c B /( c A + c B ) T B = (1 – “slope”) T B . (a) We observe that the “y intercept” is 150 K, so T B = 150/(1 – “slope”) = 150/(3/5) which yields T B = 2.5×10 2 K. (b) As noted already, c A /( c A + c B ) = 2 5 , so 5 c A = 2 c A + 2 c B , which leads to c B / c A = 3 2 =1.5....
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This note was uploaded on 06/03/2011 for the course PHY 2049 taught by Professor Any during the Spring '08 term at University of Florida.

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