Apiston-cylinder device contains 0.02 m3 of hydrogen at 300 k. it has a diameter of 10 cm. the piston (assumed weightless) is pulled by a connecting rod perpendicular to the piston surface. if the outside conditions are 100 kpa and 300 k, (a) determine the pull force necessary in kn to create a pressure of 50 kpa inside. (b) the piston is now released; as it oscillates back and forth and finally comes to equilibrium, the temperature inside is measured as 600 k (reasons unknown). what is the pressure of hydrogen at equilibrium

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 the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct.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.