Awell insulated piston-cylinder assembly contains 0.5 kg of air initially at a pressure of 300 kpa and a temperature of 75°c. the air temperature is increased to a temperature of 150°c by an electric resistance heating element inside the cylinder at constant pressure b. c. d. determine the total change in internal energy of the air. calculate the work done by the system during the process. find the amount of heat supplied by the heating element.

To save energy, the air supply to a 2000 ft office has been shut off overnight and the room temperature has dropped to 40°f. in the morning, the thermostat is reset to 70°f and warm air at 120 f begins to flov in at 200ft'/min. the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct. the air pressure is nearly 1 atm everywhere. ignoring heat transfer with the surroundings and kinetic and potential energy effects, estimate how long it takes for the room temperature to reach 70°f. plot the room temperature as a function of time.