UNIFIED ENGINEERING Fall 2004
Ian A. Waitz
Problem T2 (Unified Thermodynamics)
An electric motor draws 3 A from the 12 V battery shown below. After 50 seconds of operation the 100 kg piston is raised a distance of 0.1m. The area of the piston, which can be considered to move without friction, is 0.05 m^2, and the atmospheric pressure is Patm = 10^5 N/m2.
a) What is the work input to the gas from the motor during the 50 s period?
b) What is the work to raise the piston?
c) What is the work done against the pressure of the atmosphere?
d) What is the net work done by the gas in the chamber during the 50 s period?
e) If the final value of internal energy were the same as the initial value, what is the heat transfer to or from the surroundings during this period?