Heheh, 3:58.. Hehehe I remember doing this experiment and that was the conclusion I wrote on my paper. I remember the teacher had to clarify for the class that the suction relied upon the cooling of the gas. LOL!
You really could have proven that it was volume change because of thermal differences by causing the water level in the glass to go back down by using a hair dryer to re-heat the air in the glass.
You said: "The oxygen is converted into carbon-dioxide. The mass stays the same".
But it's not the mass that matters, it's the volume. If carbon-dioxide happened to have a much higher density than oxygen, that would still cause it to suck the liquid in. (As it is, of course, that doesn't matter. Just saying.)
Ok, I was doing this project for school, and this proved it false. :D So I can say this new thing thanks to you. But, I'm still in a little bit of a problem. I need to find an application for this in real life, but I can't think of any. Anyone wanna help me? Please reply to this comment
This concept is very important to firefighters. You know about the fire triangle: heat, fuel, and oxygen. A fire might consume all of the oxygen in the room and go out, with the heat and fuel remaining. As soon as the firefighter opens the door or busts a window, the sudden influx of oxygenated air can start the fire right back up. It's incredibly dangerous and part of their training is dealing with precisely this situation.
Actually I read this "oxygen consumption" thing on some cheap science book for kids and I tried it to confirm it and was amazed :P
What made me suspicious though was the fact that the water level did not raise by 20% of the height of the glass. Hehe, too bad I never actually looked for an alternate explanation.
PS the "oxygen doesn't disappear" fact is called conservation of matter. I thought the candle turned the oxygen into something more dense, therefore taking less volume.
Actually, it's conservation of energy (matter and energy are the same thing). And there may be something to your last point; Mooeypoo has been trying to get a definitive answer as to what exactly is going on. It looks like I'm mostly right, but there's other stuff going on, too.
I got it! You would prove that it's cooling air which creates the vacuum by lighting the candle whilst it's inside the glass. That way expanded air would remain inside the glass and will not affect the end result. Use a bigger glass to let the hot air cool at the top of the glass and thus not cause air to escape from below the glass. Water level should remain the same
To do that you can use electrical wires which go inside the glass from under the water which will spark the candle into a flame.
Yeah, striking a match has all kinds of ramifications outside the scope of this experiment. Using an electronic lighter to light an actual candle might be better.
Oh man, please, please pleeeeaaase tell me you're joking, when you're saying that physics teachers actually teach kids that it's because the candle is "eating" the oxygen. I mean, every 10 year should know about temperatures' effect on barometric pressure (not in those words of course). Educational standard on your side of the Atlantic must be worse than I thought.
im doing this projectXDit happens because the candle heats the air inside the glass which causes low pressure but the pressure outside is still has a higher pressure then the inside so the air outside forces itself into the glass which also takes water with it that makes a vaccum like suction so it takes the water from around the container into the glass
I think her experiment worked better than yours is because the shape of the plate. I would think if you used an identical plate, it would have worked better.
Hey, Shane, I thought you might be interested that I am working in tandem with Chemistry professor and a Physics professor at my university; apparantly, it's more complicated than just the heat, or "just" more moles that are produced.
I think you missed the point. Not everything the teacher says is a lie, but when they have to teach complex ideas, they start with simple ideas that are not exactly correct, and progress to ideas that are more correct.
I remember doing that water experiment too, but I was in the 3rd grade and probably wouldn't have understood the air contraction explanation at that time, but the fire eating the oxygen explanation I understood with no problems.
Shane, you are right in that temperature causes most of the pressure difference. But there is a pressure difference as well. Recall that the end products of combustion are not all gaseous.
CH4 + 2O2 → CO2 + 2H2O
Aquatic animals that carry an external water reserve face the same problem. The airbubble diminishes as they consume oxygen and produce carbon dioxide and water. Of course there is also diffusion of oxygen to the surrounding water, but that effect aside, pressure drops, bubble shrinks.
I know that respiration is a different reaction than normal fire combustion. The same principle applies though, and that's why I used the practical example with aquatic animals.
Great video, shane!
"Science is interesting, and if you don't agree you can fuck off." - Alun Anderson, Editor-in-Chief of New Scientist.
Damn, I didn't realize that moo has a new channel. You're right, she's awesome, and the first ever person I was subscribed to here on yt. So thanks for pointing me there ;-)
Also, nice experiment, even though I knew it before ;-)
Has any one done the expiriment where you Fill a glass bottle partially with cold water (or just take a glass bottle and put it in the freezer for a while). Then you place a quarter or a dime on the mouth of the bottle and wrap your hands around it. The warming of the air in the bottle will make the coin jump. Same principle, but reverse. You may need to wet the mouth of the bottle for a better seal.
I think they did something similar in the promo for "The Skeptologists." There's a small jar with a wood block on top, and the block spontaneously jumps off. I'm guessing they had warm air (or some other kind of gas) in the jar, and when it cooled it pushed up on the block and knocked it off.
I tried this, and the water didn't rise as high. I figured, "Of course, there's not a candle there displacing the water, you idiot!" and I put an identical candle next to it, unlit.
I held the glass above the lit candle, then put it over the unlit candle...and the water STILL didn't rise as high. As near as I can figure, it's losing some heat out the bottom where before it was all retained.
Yes, I predicted that, but dang it, didn't include it in my comment! I'm not sure how to do the experiment to account for the loss from the bottom. Any container, even a large one, will be filled with hot air by the candle all the way to the bottom, and that hot air can be lost.
What I think might increase the effect is holding the glass over the candle for a while before placing it into the water. Also holding the glass at an angle as you did the second time (in the video) will help facilitate the replacement of cooled air with hot air. And use a hot glass. By preheating the glass you will ensure the air already heated molecules in the glass. Basically you want the air as hot as possible before putting it in the water.
Ever since I started helping dad wash the dishes I've always noticed that an upended warm glass on a bench top with a slick of water would stick via the suction from the cooling air it contained. I would wager that using simply a hot glass without the candle would suck more liquid up than with just the candle as long as you allow the hot glass to warm the air inside it by holding it just above the water for a moment.
The amount of heat absorbed by the glass would be larger than the amount of heat emitted by the candle in the time before it gets extinguished. A glass heated by filling it with hot water from the hot tap would suffice. Of course, I will always pay my wager if proved wrong. (For the fools among us WEAR OVEN GLOVES!!!)
Ok, I tried the hot water from tap technique last night will doing the dishes and the results were, in a word, pathetic. So I accept defeat in that.
But this morning while making a cup of tea I tried heating the glass with boiling water. And the results were excellent! The water level rose 6 full centimeters!!!!
Hot tap water simply wasn't enough, I would suggest that heating the air with the candle prior to positioning in the water would cause as dramatic effect.
Fire "consumes" O2 and produces CO2; that means that there are less moles eventually, which means that the pressure is lower than that of the "outside" environment.
Isnt' that, beyond the "heating" of the oxygen, what causes the rise of the liquid inside?
Note that n doesn't say anything about the kind of molecule, curiously. Set pressure, volume and temperature and there is only one possible value for the gas n!
Everything's atmospheric before. After, I agree, the gas inside the glass is lower pressure but not as low as it would have been if
it had not lost volume. Rising water allowed the final pressure to be higher than it otherwise would have been in a sealed container. So it's a combination! This is actually a rather complex experiment ...
Man, you rule. You saved me up the trouble of re-doing the experiment, and showed it wonderfully. Many many thanks!
There's no shame in getting things wrong, it's part of learning; there's even better dignity in having your experiment repeated - that's the scientific method.
All my class mates hated it when I argued with the teacher about this one. I don't know why it's such a universal method of teaching kids how to measure the level of oxygen in the air when it's so flawed.
How dare you disrespect the honor and wisdom that the lab coat brings. Obviously I am talking to man that has never seen John Pendleton. Shame on you Shane! Shame! Shame! Shame! /end sarcasm
I remember doing that experiment in primary school, (around year 3 or 4 I think), but we were given a reasonably correct explanation for it. Maybe I was just lucky to get a teacher who knew what she was talking about.
It's like the Bernoulli effect allegedly solely responsible for birds' lift according to school textbooks. In reality, it's mainly because of the faster flowing air "above" the bent wing being less dense than "beneath" it, thus pushing the wing (quote marks because the lift works in any direction, not just upwards in case of a horizontally adjusted wing).
Yes, and at the same time they taught us that planes could not fly upside-down, which is absolutely untrue. Stunt pilots do it all the time. It's just because you've got more air molecules bouncing off the underside of the wing than you do the top.
Correct me if I am wrong, but "it's mainly because of the faster flowing air 'above' the bent wing being less dense than 'beneath' it, thus pushing the wing"
Ummm, that is the Bernoulli principal isn't it? An increase in air velocity creates a decrease in pressure.
Yes, but velocity is direction as well as speed. The point is not so much that it's moving faster, it's that it's moving AWAY from the wing, while underneath it's moving TOWARDS (and bouncing off of) the wing. They ignore the direction part when they teach you about it.
Heheh, 3:58.. Hehehe I remember doing this experiment and that was the conclusion I wrote on my paper. I remember the teacher had to clarify for the class that the suction relied upon the cooling of the gas. LOL!
GuitarMannnnnn 1 month ago
You really could have proven that it was volume change because of thermal differences by causing the water level in the glass to go back down by using a hair dryer to re-heat the air in the glass.
YngMaji1 1 year ago
You said: "The oxygen is converted into carbon-dioxide. The mass stays the same".
But it's not the mass that matters, it's the volume. If carbon-dioxide happened to have a much higher density than oxygen, that would still cause it to suck the liquid in. (As it is, of course, that doesn't matter. Just saying.)
Mithcoriel 2 years ago
@Mithcoriel It is the exact same volume. The volume of air within the glass remains constant during the entire process, and the mass does too.
dudemanguy3333 1 year ago
Question: How many creationists have used this as a reason to question evolution taught in schools?
Surhotchaperchlorome 3 years ago
So, whatever became of mooeypoo, anyway?
TomSFox 3 years ago
Ok, I was doing this project for school, and this proved it false. :D So I can say this new thing thanks to you. But, I'm still in a little bit of a problem. I need to find an application for this in real life, but I can't think of any. Anyone wanna help me? Please reply to this comment
Lightercutt 3 years ago
This concept is very important to firefighters. You know about the fire triangle: heat, fuel, and oxygen. A fire might consume all of the oxygen in the room and go out, with the heat and fuel remaining. As soon as the firefighter opens the door or busts a window, the sudden influx of oxygenated air can start the fire right back up. It's incredibly dangerous and part of their training is dealing with precisely this situation.
shanedk 3 years ago
Actually I read this "oxygen consumption" thing on some cheap science book for kids and I tried it to confirm it and was amazed :P
What made me suspicious though was the fact that the water level did not raise by 20% of the height of the glass. Hehe, too bad I never actually looked for an alternate explanation.
PS the "oxygen doesn't disappear" fact is called conservation of matter. I thought the candle turned the oxygen into something more dense, therefore taking less volume.
mtanti87 3 years ago
Actually, it's conservation of energy (matter and energy are the same thing). And there may be something to your last point; Mooeypoo has been trying to get a definitive answer as to what exactly is going on. It looks like I'm mostly right, but there's other stuff going on, too.
shanedk 3 years ago
Are you sure that matter and energy are the same thing or is it just matter and energy can be transformed into each other?
Here's another plausible explanation, god did it :P
Why don't you use a thermometer to check just how quickly the air in the glass cools down. You could then easily use physics to check your hypothesis.
mtanti87 3 years ago
I got it! You would prove that it's cooling air which creates the vacuum by lighting the candle whilst it's inside the glass. That way expanded air would remain inside the glass and will not affect the end result. Use a bigger glass to let the hot air cool at the top of the glass and thus not cause air to escape from below the glass. Water level should remain the same
To do that you can use electrical wires which go inside the glass from under the water which will spark the candle into a flame.
mtanti87 3 years ago
I've been thinking about that, but the ways I can think to do the experiment would be too difficult and expensive to set up.
shanedk 3 years ago
Just did the experiment myself. I lighted a match inside a jar on water. Here are the results:
As soon as I lighted the match, the water level went down by 6mm.
As soon as the match extinguished, the water level went back up by 3mm.
Possible errors:
Sulfur gas from the match might have increased the volume of gas in the jar.
Match could have extinguished before all the oxygen was consumed (coz that's what matches do :P)
Will make a video of it when I get the chance.
mtanti87 3 years ago
Yeah, striking a match has all kinds of ramifications outside the scope of this experiment. Using an electronic lighter to light an actual candle might be better.
shanedk 3 years ago
The spark thing didn't work with 2 LR14/C batteries in series. How about you try it with your car battery? :P
mtanti87 3 years ago
An electric barbecue lighter should be fine, if you can waterproof it.
shanedk 3 years ago
Me again! Check this out:
C_25_H_52 + 38 O_2 => 25 CO_2 + 26 H_2_O
The chemical reaction in a burning candle. Notice however that as the amount of oxygen reduces, more carbon is produced which results in sooth.
Now given that the temperature of the air in the jar will be 1800K (candle flame), these are the densities (kg/m^3):
CO_2 : 0.3
H_2_O : 5.95
O_2 : 0.22
Therefore in the ratio of the chemical equation you burn 1/8.36 m^3 of oxygen and replace it with 1/152.84 m^3 of produced gases. Errors?
mtanti87 3 years ago
"If you're like me, and I know I am..."
Ha! Never caught that one before!
TomSFox 3 years ago
Oh man, please, please pleeeeaaase tell me you're joking, when you're saying that physics teachers actually teach kids that it's because the candle is "eating" the oxygen. I mean, every 10 year should know about temperatures' effect on barometric pressure (not in those words of course). Educational standard on your side of the Atlantic must be worse than I thought.
Finkeren 3 years ago
I know only that that's what I was taught, and that others were taught the same thing. I have no idea how prevalent it is/was.
shanedk 3 years ago
Thumbs up for trying to get some basic science out there anyways :-)
Finkeren 3 years ago 2
im doing this projectXDit happens because the candle heats the air inside the glass which causes low pressure but the pressure outside is still has a higher pressure then the inside so the air outside forces itself into the glass which also takes water with it that makes a vaccum like suction so it takes the water from around the container into the glass
dogyasha 3 years ago
There's a book called "Lies My Teacher Told Me."
civisromae 3 years ago
I hope it wasn't written by Kent Hovind.
TomSFox 3 years ago 2
No, it was written by somebody who knew what he was talking about.
civisromae 3 years ago
If Hovind were telling the truth about having taught high school science for 15 years, he might well be the subject of that book.
civisromae 3 years ago
This trick is better when you try to get a boil egg into a bottle.
big46uk 3 years ago
"if you're like me, and I know I am"
that's funny.
I think her experiment worked better than yours is because the shape of the plate. I would think if you used an identical plate, it would have worked better.
lennyhipp 3 years ago
Very interesting video. I actually learned something. (During April vacation? Blasphemy!)
Andy120290Returns 3 years ago
Hey, Shane, I thought you might be interested that I am working in tandem with Chemistry professor and a Physics professor at my university; apparantly, it's more complicated than just the heat, or "just" more moles that are produced.
Expect a follow-up video :)
smarterthanthat 3 years ago
Looking forward to it!
shanedk 3 years ago
By the way, thanks for the vid, and thanks for drawing attention to mooás new chanell!
lovasip 3 years ago
Yeah if you replace oxigen with carbon-dioxide it pretty much the same amount of gas, with the same properties.
Worse than that even steam is added to the gas. (A usual byproduct of burning organic materials like wax)
I guess one cause of the contraction that the water condenses as the bottle cools down.
lovasip 3 years ago
Actually, it's the air inside the glass that cools down. The glass cooling down wouldn't change its volume enough to make any visible difference.
shanedk 3 years ago
Yes. What I meant is the air inside the glass.
As it cools down loses its humidity thus the pressure drops.
I did the experiment and I noticed that as the light goes off and the water starts to rise humidity appears on the glass.
I only have a shitty webcam and an even shittier phonecam, but doing a second vid focusing on this phenomenon would be a good idea.
lovasip 3 years ago
Have you ever heard of "Lies to Children" (LTC).
Teachers tell them all the time to help students understand concepts before they can understand a lesser lie.
Here's an example of a 3 level LTC.
LTC level 1: Weight is constant.
LTC level 2: Weight is not constant. Mass is constant.
LTC level 3: For "special relativity", mass is not constant, but "invariant mass" is.
Atriviality 3 years ago
Okay, so why are they teaching my daughter she only has five senses?
shanedk 3 years ago
I think you missed the point. Not everything the teacher says is a lie, but when they have to teach complex ideas, they start with simple ideas that are not exactly correct, and progress to ideas that are more correct.
I remember doing that water experiment too, but I was in the 3rd grade and probably wouldn't have understood the air contraction explanation at that time, but the fire eating the oxygen explanation I understood with no problems.
Atriviality 3 years ago
Shane, you are right in that temperature causes most of the pressure difference. But there is a pressure difference as well. Recall that the end products of combustion are not all gaseous.
CH4 + 2O2 → CO2 + 2H2O
Aquatic animals that carry an external water reserve face the same problem. The airbubble diminishes as they consume oxygen and produce carbon dioxide and water. Of course there is also diffusion of oxygen to the surrounding water, but that effect aside, pressure drops, bubble shrinks.
smaakjeks 3 years ago
I know that respiration is a different reaction than normal fire combustion. The same principle applies though, and that's why I used the practical example with aquatic animals.
Great video, shane!
"Science is interesting, and if you don't agree you can fuck off." - Alun Anderson, Editor-in-Chief of New Scientist.
smaakjeks 3 years ago
Correction of myself:
"Shane, you are right in that temperature causes most of the pressure difference. But there is a pressure difference as well."
I meant to say that there is a difference in pressure due to the consumption of oxygen as well.
smaakjeks 3 years ago
Okay, this seems to answer the above questions. Thanks!
shanedk 3 years ago
Damn, I didn't realize that moo has a new channel. You're right, she's awesome, and the first ever person I was subscribed to here on yt. So thanks for pointing me there ;-)
Also, nice experiment, even though I knew it before ;-)
Killersepp 3 years ago
Thanks for enlightening me. I also has this misconception buit you're absolutely right! Kudo's.
uthamal 3 years ago
"If you're like me and I know I am..." hehe.
TheRealBladeRunner 3 years ago
Has any one done the expiriment where you Fill a glass bottle partially with cold water (or just take a glass bottle and put it in the freezer for a while). Then you place a quarter or a dime on the mouth of the bottle and wrap your hands around it. The warming of the air in the bottle will make the coin jump. Same principle, but reverse. You may need to wet the mouth of the bottle for a better seal.
pmokadakeisuke 3 years ago
I think they did something similar in the promo for "The Skeptologists." There's a small jar with a wood block on top, and the block spontaneously jumps off. I'm guessing they had warm air (or some other kind of gas) in the jar, and when it cooled it pushed up on the block and knocked it off.
shanedk 3 years ago
Ok, nice one Shane. But if you are right there is a simple control experiment you can do. Put the glass over the flame to heat the air inside.
Then set the glass down NEXT TO the flame
(you will need a pan for this). If it is cooling of the air, it should rise in that case too.
farvision 3 years ago
Or just put hot anything above the glass to keep the air hot.
I might try that actually.. it's ... interesting... hmm.
smarterthanthat 3 years ago
I'll be waiting for the video! :-)
(Thought about doing it myself but would
have to get a candle ... and I'm not set up to do videos.)
farvision 3 years ago
I tried this, and the water didn't rise as high. I figured, "Of course, there's not a candle there displacing the water, you idiot!" and I put an identical candle next to it, unlit.
I held the glass above the lit candle, then put it over the unlit candle...and the water STILL didn't rise as high. As near as I can figure, it's losing some heat out the bottom where before it was all retained.
shanedk 3 years ago
Yes, I predicted that, but dang it, didn't include it in my comment! I'm not sure how to do the experiment to account for the loss from the bottom. Any container, even a large one, will be filled with hot air by the candle all the way to the bottom, and that hot air can be lost.
farvision 3 years ago
That, and you're not getting the full heat from the candle to begin with. A lot of it radiates out the sides, under the glass.
shanedk 3 years ago
What I think might increase the effect is holding the glass over the candle for a while before placing it into the water. Also holding the glass at an angle as you did the second time (in the video) will help facilitate the replacement of cooled air with hot air. And use a hot glass. By preheating the glass you will ensure the air already heated molecules in the glass. Basically you want the air as hot as possible before putting it in the water.
amcnea 3 years ago
Ever since I started helping dad wash the dishes I've always noticed that an upended warm glass on a bench top with a slick of water would stick via the suction from the cooling air it contained. I would wager that using simply a hot glass without the candle would suck more liquid up than with just the candle as long as you allow the hot glass to warm the air inside it by holding it just above the water for a moment.
kevinpluck 3 years ago
(Continued - 500 characters! SHEESH)
The amount of heat absorbed by the glass would be larger than the amount of heat emitted by the candle in the time before it gets extinguished. A glass heated by filling it with hot water from the hot tap would suffice. Of course, I will always pay my wager if proved wrong. (For the fools among us WEAR OVEN GLOVES!!!)
kevinpluck 3 years ago
Ok, I tried the hot water from tap technique last night will doing the dishes and the results were, in a word, pathetic. So I accept defeat in that.
But this morning while making a cup of tea I tried heating the glass with boiling water. And the results were excellent! The water level rose 6 full centimeters!!!!
Hot tap water simply wasn't enough, I would suggest that heating the air with the candle prior to positioning in the water would cause as dramatic effect.
kevinpluck 3 years ago
Yeah, I thought that as I watched the video afterwards. I also think my candle was more slowly burning than Moo's.
shanedk 3 years ago
aaaaaand another thing -- a question, if you may.
Fire "consumes" O2 and produces CO2; that means that there are less moles eventually, which means that the pressure is lower than that of the "outside" environment.
Isnt' that, beyond the "heating" of the oxygen, what causes the rise of the liquid inside?
smarterthanthat 3 years ago
Maybe god did it.
TomSFox 3 years ago
1 mole of CO2 = 1 mole of O2. Lessee pv=nrt.
pressure times volume is number of moles,
gas constant, temperature.
R constant, P constant (!), volume v
inversely related to t. I think n is constant!
Note that n doesn't say anything about the kind of molecule, curiously. Set pressure, volume and temperature and there is only one possible value for the gas n!
farvision 3 years ago
But pressure is not constant. That's the whole point of the experiment, farvision.
smaakjeks 3 years ago
Looks like smaakjeks answered this below.
shanedk 3 years ago
smaakjeks, it's rather subtle. In thermodynamics
one counts the two states before and after.
Everything's atmospheric before. After, I agree, the gas inside the glass is lower pressure but not as low as it would have been if
it had not lost volume. Rising water allowed the final pressure to be higher than it otherwise would have been in a sealed container. So it's a combination! This is actually a rather complex experiment ...
farvision 3 years ago
Someone more knowledgeable than me will have to address this.
shanedk 3 years ago
By the way, I just added your video to the post, so now people can see the original video *AND* your corrected explanation in one post.
Cheers :)
smarterthanthat 3 years ago 2
Man, you rule. You saved me up the trouble of re-doing the experiment, and showed it wonderfully. Many many thanks!
There's no shame in getting things wrong, it's part of learning; there's even better dignity in having your experiment repeated - that's the scientific method.
Cheers!
smarterthanthat 3 years ago 2
Yes, it's nice to be able to admit when you are wrong.
Unfortunaly, I'm never wrong.
TomSFox 3 years ago
All my class mates hated it when I argued with the teacher about this one. I don't know why it's such a universal method of teaching kids how to measure the level of oxygen in the air when it's so flawed.
Libertarianist 3 years ago 2
How dare you disrespect the honor and wisdom that the lab coat brings. Obviously I am talking to man that has never seen John Pendleton. Shame on you Shane! Shame! Shame! Shame! /end sarcasm
jimsartor 3 years ago
I'm totally using alcohol to do this experiment now. AND I'm not going to get my parents permission.
rnistuk 3 years ago
We have a rebel on our hands, people.
AisuSeijin 3 years ago 4
FREE THINKER ALERT!
Killersepp 3 years ago
I wonder if the effect would've been exaggerated had the glass just been removed from the freezer immediately before the experiment.
kjlg74 3 years ago
Perhaps, but I doubt it. It happens very quickly as it is. You're welcome to try it, of course. ;^P
shanedk 3 years ago
I remember doing that experiment in primary school, (around year 3 or 4 I think), but we were given a reasonably correct explanation for it. Maybe I was just lucky to get a teacher who knew what she was talking about.
lachlanhunt 3 years ago
It's like the Bernoulli effect allegedly solely responsible for birds' lift according to school textbooks. In reality, it's mainly because of the faster flowing air "above" the bent wing being less dense than "beneath" it, thus pushing the wing (quote marks because the lift works in any direction, not just upwards in case of a horizontally adjusted wing).
leporidus 3 years ago
Yes, and at the same time they taught us that planes could not fly upside-down, which is absolutely untrue. Stunt pilots do it all the time. It's just because you've got more air molecules bouncing off the underside of the wing than you do the top.
shanedk 3 years ago
Correct me if I am wrong, but "it's mainly because of the faster flowing air 'above' the bent wing being less dense than 'beneath' it, thus pushing the wing"
Ummm, that is the Bernoulli principal isn't it? An increase in air velocity creates a decrease in pressure.
amcnea 3 years ago
Yes, but velocity is direction as well as speed. The point is not so much that it's moving faster, it's that it's moving AWAY from the wing, while underneath it's moving TOWARDS (and bouncing off of) the wing. They ignore the direction part when they teach you about it.
shanedk 3 years ago
True thinking at work
Xestriker 3 years ago
I used to do that one as a teenager, and I also had it wrong until I read the correct explanation.
That's what you can get in any experiment without proper controls and measurements.
shockferret 3 years ago 2