Fermi would know that the average human hanging out is roughly a 100 Watt device...

The Fermi problem.

"Fermi estimate is an estimation problem designed to teach dimensional analysis, approximation, and the importance of clearly identifying one's assumptions. Named for 20th century physicist Enrico Fermi, such problems typically involve making justified guesses about quantities that seem impossible to compute given limited available information."

This applies to everything. Social science, is there life beyond our solar system, how many jelly beans in a jar... A great one tried out, that has an answer I would guess because of my (underdeveloped, relatively uninterested in) biology background...

http://physicsbuzz.physicscentral.com/2009/09/answer-to-friday-fermi-problem.html

Assuming you're not in a big lecture hall and the professor shuts the door at the start of class, how long does it take for you and your classmates to deplete the oxygen enough to feel it?

The elevator problem basically... I've always thought this depended on exhale, not inhale.. almost a trick question.


Now populate the classroom with 34 students and 1 teacher. The 35 occupants consume 15.3125 liters per minute. Now for the final calculation:

2625 L x (1 minute/ 15.3125 L)

It will take about 171 minutes, or 2 hours and 51 minutes for the room to become unbearably stifling. You can image that you'd start to feel pretty uncomfortable about an hour and a half into the lecture—a good argument for shorter classes.

BUT!.. CO2!

I know I'm being very vague here... it's late, and I'm not on top of my game. But check out the Fermi problem.. it's really fascinating.. so many variables are involved despite trying to keep variables down. Anyway, the Fermi problem extends well beyond this physics app, obviously.