hw6.pdf - <Homework 6> 1 A thick aluminum rod and a thin steel wire are attached in parallel as shown in the figure The temperature is 20C Both the rod

hw6.pdf - <Homework 6> 1 A thick aluminum rod and a thin...

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<Homework 6> 1. A thick aluminum rod and a thin steel wire are attached in parallel, as shown in the figure. The temperature is 20°C. Both the rod and the wire are 85 cm long and neither is under stress. The system is heated to 150°C. Calculate the resulting stress in the wire, assuming that the rod expands freely. 2. A composite bar of length L = L 1 + L 2 is made from a bar of material 1 and length L 1 , attached to a bar of material 2 and length L 2 . Show that the effective coefficient of linear expansion for this is given by = ( α α α 1 L 1 + α 2 L 2 )/L. 3. A sample of gas expands from 1.0 to 4.0 m 3 while its pressure decreases from 40 to 10 Pa. How much work is done by the gas if its pressure with volume according to each of the three processes shown in th p-V diagram as below? 4. Consider 100J of work are done on a system and 70 cal of heat are extracted from the system. In the sense of the first law of thermodynamics, what are the values (including algebraic signs) of W, Q and internal energy respectively?