SolutionHW6-new

# SolutionHW6-new - ME311 MATERIALS ENGINEERING HOMEWORK#6 PROBLEM 1 As a mechanical analogue of thermodynamic phase metastability consider the

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ME311 MATERIALS ENGINEERING HOMEWORK #6 PROBLEM 1: As a mechanical analogue of thermodynamic phase metastability, consider the potential energy of a block of mass m resting on a horizontal plane (figure below). Based on the information given in figure 2, sketch in a diagram (potential energy (mgh) vs angle of tilt ( θ )) the variation of potential energy of block with angle tilt θ in going from situation 1 to to 2, and subsequently from 2 to situation 3. What is the change in potential energy at the end of each transition SOLUTION PROBLEM 2:

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Consider a portion of the H 2 O-NaCl phase diagram (see figure below). Using this diagram, answer the following questions: a) Why adding salt on ice at a temperature below 0 C can cause the ice to melt? b) At -10 C what is the amount of salt you need to add to completely melt the ice? What about at –25 C? c) What is the concentration of salt in the brine at –20 C? d) What concentration of salt is necessary to have a 50% ice-50% liquid brine at -10C? SOLUTION a. Spreading salt on ice will lower the melting temperature, since the liquidus line decreases from 0 C to the eutectic temperature at about –21 C. Thus, ice at a temperature below 0 C (and above –21 C) can be made to form a liquid phase by the addition of salt. b.
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## This note was uploaded on 04/03/2012 for the course ME 311 taught by Professor Meyers during the Spring '08 term at University of Texas at Austin.

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SolutionHW6-new - ME311 MATERIALS ENGINEERING HOMEWORK#6 PROBLEM 1 As a mechanical analogue of thermodynamic phase metastability consider the

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