How Long Would It Take a Physics Lecture to Actually Kill You?

By Brett Israel | September 16, 2009 5:22 pm

To honor the start of a new school year, we bring to you the following Fermi problem: How long would a physics lecture have to be to actually kill you?

Or more precisely, from Physics Buzz:

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 mathletes at the Buzz make a few assumptions about the classroom, but in a 16-foot by 16-foot classroom with a 10-foot ceiling, packed with 34 bleary-eyed students and one Red Bull fueled professor the answer is…2 hours and 51 minutes!

Of course you’ll probably be brain dead long before that point.

Check their math here and then tell us why they’re right or wrong, or if you’ve ever survied such a physics marathon.

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Image: flickr / Rober S. Donovan

• Brian

Depends entirely upon the rate of oxygen consumption by the windbag up front!

• Mike Soso

If the professor puts everyone to sleep, they’ll all live longer.

• Doug

Surely flatulence from a whole class in an unventilated room is going to become health threatening before oxygen depletion.

• Nanite

Yeah, because every lecture hall is airtight and NO air every leaks in or out of the room from cracks in the door/window/AC vents etc.

The calculations should include air leaks.

• ToNanite

…You are truly an asshole and a fun killer…

• NanitesRight

Nanite’s right, but there’s one of those buzz-killers in every class. I don’t think this was meant to be statistically significant. Laugh it up man.

• Hedzer

Mike Soso is right, given the length of time of the lecture they should factor in people who fell asleep (they consume less oxygen). Then again this is done with the std “ideal” environment where leaks are not taken into account, or professor fatigue, or room temp/vs CO2 dist.
Wait, why did I write all of this? this is after all just a fun exercise, I wish all text book exercise were like this one.

• http://N/A Bob Haggerty

I believe the wrong question is being asked. Nanite’s reasonable assertion aside, the operative limiting factor will be CO2 build up. CO2 will reach critical levels long before lack of oxygen is a problem AND assuming the class was told to “shelter in place” having brought the necessary duct tape and plastic to seal the room adequately, George Bush and the boys having declared a red – threat level.

What’s that you say? W’s no longer president? Oh sorry I hadn’t noticed.

Apollo 13 is an anecdotal case in point. CO2 rose to dangerous levels when the CO2 scrubbers (soda lime which absorbs the carbon dioxide) in the LEM exceeded their life span.

In the interest of good humor (at the expense of good science) …

Given that the rise in CO2 and methane levels will cause an increase in ambient temperature, atomic activity will be excited. This will lead to an increase in quarks “popping out”, which will be noticed by the brains of the students. Those brains which are sufficiently flexible will see how it is done, will also “pop out”, leaving more oxygen for the remaining students. The instructor, on the other hand, will be distracted by the lecture he is presenting, and will not learn to pop out – thus, the students will surpass the master!

• Alfonso

in order for this to be an actual physics experiment the room should be spherical

• Marc Sher

If the room is thermally insulated, the temperature will rise by about 20 degrees Celsius per hour. That will boil everyone long before the air runs out (assuming the room is full of 100-W students, using the specific heat of a diatomic gas…)

• mheyman

In a thermally insulated room, the temperature will rise which will cause a corresponding rise in pressure. The over pressure will cause the classroom, which isn’t designed for overpressure, to rupture. Thus, with the destruction of the physics hall, the students will survive.

• Randy Goat

As CO2 is heavier than O2, the cracks in the ceiling are disadvantageous. The crack under the door, methane emissions & the number of students in heavy trance should prolong the agony up to 6 hours, but they should be feeling it the minute the geezer loses his place in his teaching guide.

• Alex

How long would it take a math lecture in marketing class because the room is not suited to mathmatical words and consumption it will decrease the rate of osmosis on to your desk. Yum.

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