1. A quantity of heat is added to the machine shown below, causing the gas to ex

Question

1. A quantity of heat is added to the machine shown below, causing the gas to expand and to raise the piston and mass 10 cm. The piston has an area of 2 in^2 and weighs 1 lbm. The mass m is 2 lbm. Atmospheric pressure is 14.7 lbf/in2. Using the information about the surroundings ONLY, calculate the work done by the system in units of ft-lbf when the system is defined by (a) boundary A; (b) boundary B; (c) boundary C 2. (a) The piston is frictionless and leak proof and the expansion may be assumed reversible. Calculate the gas pressure in the cylinder of the machine shown below when: (i) the atmospheric pressure is 14.7 Ibf / in2 absolute (psia); (ii) the surroundings' absolute pressure is zero. (b) Calculate the reversible work done by system A from the changes in the system's properties (the pressure and volume change). Compare with the result in problem 1 (a). (c) Is it possible to calculate the work from information concerning the system properties when the external pressure is absolute zero? Why or why not? (d) Suggest a design change in this machine that would decrease the work of atmospheric displacement without changing the useful (mass-raising) work. Would this change affect the cylinder pressure?

Explanation / Answer

13.6

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