Global positioning satellites (gps) can be used to determine your position with great accuracy. if one of the satellites is 20,000 km from you, and you want to know your position to 2m, what percentage uncertainity is required?

On a mild saturday morning while people are working inside, the furnace keeps the temperature inside the building at 23degreesc. at noon the furnace is turned off, and the people go home. the temperature outside is a constant 16degreesc for the rest of the afternoon. if the time constant for the building is 3 hr, when will the temperature inside the building reach 18degreesc? if some windows are left open and the time constant drops to 2 hr, when will the temperature inside reach 18degreesc?