How long does a physics lesson have to be to really kill you?
In honor of the beginning of the school year, you have a problem: how long does a physics lesson have to be to really kill you? Or to be precise: if we assume that you are in a not very large class, and the teacher closes the door at the beginning of the lesson, how long will it take until you and your classmates lower the oxygen level in the room to a point where you can feel it?
The physics buzz blog writer suggests Answer: Suppose the dimensions of the classroom are 5 meters long, 5 meters wide, 3 meters high (roughly like a school classroom), then the volume of the classroom is 75 square meters. There are 1000 liters in a square meter. So the classroom in question has 75,000 liters of air. The concentration of oxygen in the air is about 21% and when it reaches about 17.5% we will feel it enough to run away from the classroom.
A quick calculation leads to 2,625 liters of oxygen to be breathed. An average person consumes about 630 liters of oxygen per day. We will transfer to measurements of a minute: (630 L/day) x (1 day/24 hours) x (1 hour/60 mins) and we will get 0.4375 liters per minute per person. Multiply by 35 people in the room (34 students + teacher) and we get a consumption of 15.3125 liters per minute. How long will it take to consume 2,625 liters? 2625 L x (1 minute/ 15.3125 L) about 171 minutes or 51 hours and XNUMX minutes for the room to become unbearably stuffy. The feeling of discomfort will start after about an hour and a half (hey! That's exactly double class!!). Of course, if the teacher will succeed in putting the students to sleep, their oxygen consumption will decrease and the class will be able to be extended...
22 תגובות
Say you live in a movie? 35 students in 5X5X3??? What about windows? What about an air conditioner? Haha...
Section section!
What a piece, Felix Brett also taught me a few years ago... lol... he really is an excellent teacher...
You can simply add a few pots in the room and with appropriate lighting extend the lesson even more.
for a physicist
The rate of our breathing is mainly influenced by the concentration of carbon dioxide in the blood. Therefore, when the concentration of carbon dioxide in the air increases, it is likely that the students in the class will start breathing faster as the body tries to get rid of excess carbon dioxide.
Not only physics, also physiology:
Normal breathing volume per minute - 6 liters
A considered normal number of breaths per minute - about 12
Therefore, about 0.5 liters per inhalation - normal.
Asthmatics, heart patients and diabetics often breathe 15 liters per minute, and some even more.
And Shlomi Tzedek: CO2 affects breathing much more, CO2 is a regulator of breathing.
Hahahaha the article is funny and the comments are even more so!! P=
With us, usually the boring lesson is a prophet.. or Judaism too!!
hahahahaha great article!!!!….
There is nothing like a thunderous puff in a heated and closed classroom - to make the cities happy and wake the dying
What about opening windows???
And if it's winter and the classroom is closed and the air conditioner is running on heating, will this affect the oxygen levels in the room?
In language class I fell asleep much faster
So there are probably a few more parameters
that were not taken into account.
"So the volume of the classroom is 75 square meters. There are 1000 liters in a square meter"
In our places volume is measured in cubic meters and not in squares.
Avi Luz
To the physicist, I addressed this in my parenthetical response.
The calculation is not accurate because the concentration of oxygen in the air decreases over time and this is not taken into account in the time calculation (we start from the assumption that each breath that enters the lungs always contains 21 percent oxygen and this is not true, this percentage is not constant and changes over time).
Conclusion, the real time is even longer!
On the other hand, if the concentration of oxygen in the air is low, maybe the average breathing rate increases?? This is already a physiological and not a physical question, so I have no idea 🙂
Lalotm, correcting a mistake in Hebrew: volume is measured in cubic meters, not square meters. A square meter is a measure of area. In class 75000 cubic meters, not square. There are no liters in a square meter. There are 1000 liters in a cubic meter.
I'm not entirely sure but it seems to me that the CO2 level will be a much more influential factor than the oxygen level
Just so you know that physics classes are one of the things I come to school for. A lot thanks to my lecturer Dr. Brett Felix who also taught my brother who is 10 years older than me and never gets bored in his classes.
On the other hand, if it's a full lecture hall where there are 200 people, and the students are sitting above the lecturer (hall on a slope), in a two-hour class, why didn't the lecturer fall asleep????
cute :))
And there is no mention of Prof. Barak Kol - the best physics professor there is.
0.4 liters of oxygen. not air It's a reasonable size. We exchange about five and a half liters of air with each breath. A fifth of that is a liter. If we breathe about 10 times a minute, that's about ten liters of oxygen. But we put in 20 percent oxygen and also take out oxygen (I was told 16%).
Where does this figure of 0.4 liters per minute come from? Obviously we breathe a lot more. It is enough to think about how much air we inhale and a 2 liter bottle full of air.
From a rough estimate of a liter of air per breath and about 10 breaths per minute, we arrive at about 10 liters per minute, that is, about 15 liters per day.
It should also have been noted that with each breath we lower the amount of oxygen from 21 to approximately 16.5 percent.
Another interesting question, is it possible to leave the small room closed at night.
A small room of 3 x 3 x 2.8. About 25 cubic meters = 25000 liters. We will drop 5 thousand because of the furniture and the body. And we will be left with 20 thousand liters of air free and ready to breathe. (Let's say that it is allowed to breathe air exactly once and then we already breathe another air or make sure to supplement the oxygen by increasing the breathing rate).
We will sleep a third of the day and reach an air volume of 5 thousand liters. That means 3 or 4 can sleep in the same room in one night..
And as for the classroom, according to my figure of 10 liters of air consumption per minute, within 10 minutes you would feel suffocation in the classroom.
And this is another lesson in physics! God only knows what the death rate is in citizenship rates