The input to a harmonic generator is a periodic waveform v(t) = Ce^-alpha t, 0 < t < 1, T = 1 with alpha < 0. The output is to be derived through a filter which will pass only one frequency. If alpha can be adjusted, what value of alpha will give the maximum output through the filter for the second harmonic the third harmonic? the fifth harmonic?

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 the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct.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