# ps14c38 - Ph 111.01 December 12, 2008 PS 14c (38) Problem 1...

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Ph 111.01 December 12, 2008 PS 14c (38) Problem 1 = Walker P. 17-53. The figure shows the temperature of 1.000 kg of water as heat is added to the system. Suppose that such a sample of water starts at point A at time zero. Heat is added to this system at the rate of 12800 J/s. Calculate the time for the system to reach each of the following points. (a) B 26.17 s (b) C s (c) D s (d) Describe the physical state of the system at time t = 48 s. ice ice and water water water and steam steam Solution. For the first three parts we evaluate heat added using (heating water) (melting ice or vaporizing water) Qm cT L =

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using the values c = 4186 J/(kg-K) (heating water), L = 335,000 J/kg (melting ice), and L = 2,260,000 J/kg (vaporizing water). And we are given the rate of heating, 12,800 J/s Q t = (a) From A to B , the heat absorbed is Qm L = and so the time is () ( )( ) 1 kg 335,000 J/kg 26.17 s / / 12,800 J/s L t Qt === = (b) We have to add on the time to go from B to C , ( ) ( ) ( )( ) 1 kg 4186 J/ kg-K 100 K 32.70 s / / 12,800 J/s c T t Δ = So, the time from A to C is the sum of the two times above, 26.17 s + 32.70 s = 58.87 s.
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## This note was uploaded on 05/13/2010 for the course PHYSICS 111 taught by Professor Staff during the Fall '08 term at S.F. State.

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ps14c38 - Ph 111.01 December 12, 2008 PS 14c (38) Problem 1...

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