Water drains at a constant rate through a saturated soil column with a diameter of 1 ft and a height of 2.5 ft. The hydraulic head is maintained at 4.7 ft at the top of the column and 1.4 ft at the bottom. After a period of 1 hr, 0.06 ft3 of water has drained through the column. What is most nearly the hydraulic conductivity (ft/s) of the soil? a. 9.1 times 10^-6 ft/s
b. 4.6 times 10^6 ft/s
c. 3.5 times 10^-6 ft/s
d. 7.1 times 10^-6 ft/s

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 the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct.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