wow that was the exact example told in my college to explain resonance and i had that same thought of " how does a constant wind-blow cause resonance? " .. thanks for clearing this up
Hmm, I don't think that this video helps anyone by saying it strictly wasn't resonance.
The article quoted in the description makes the distinction between forced resonance and self-excitation. Not so much that this wasn't a case of resonance between the period of the bridge displacement and the force input, but rather that the two periods were intrinsically linked (force on the bridge depended on the bridge position). This combined with insufficient dampening in the system resulted in failure.
@ExtemelyStoopid instead of just craping on this video posters comment section with negative attitudes how about you post links and videos that prove it wrong or show what aeroelastic flutter really is and what causes it. You think anyone is going to take what you said as true over the video of the one minute physics guy. No and if you are going to laugh at people trying to learn something in a fun and creative way then you have no right commenting here at all.Good day sir.
@MrSumbody69 You couldn't be more incorrect. Your attitude is exactly the attitude that ruins Youtube comment sections. He didn't claim anything that he needed to prove. Moreover, learning in a fun and creative way is fantastic, but using a medium such as the internet means you have the ability to learn things wrong. You have to appreciate that that might be the case and thank people when they are willing to stand up and say so. It's for your benefit.
@tabaks I don't aim to sound smart; if that were life's aim, life would be very pointless. I'm merely saying that you can't believe everything you watch. I think that was what is being got at here. I made my opinion on the video quite clear a few comments before, so I didn't bother writing it again. Sorry if I sound like I'm trying to be a know-it-all, I just really fear for people who don't question the content they watch.
So, resonance was supposed to be the reason soldiers fall out and march at random when crossing a bridge, . . . is that pointless under this analysis? Can we prevent aeroelastic flutter?
It may not be externally induced resonance, but it's resonance none-the-less (self-induced resonance). This video is doing the same as the textbooks by over-simplifying the physics. It is still an absolutely valid example of resonance for teachers to use and for pupils to remember.
This video is all about splitting hairs to force false originality. The flutter is the CAUSE of the resonance effect. There is no new information here.
@skadar To be fair, I've read articles and have heard people say that it was because the canyons were just right for the wind to blow in pulses, so some people out there are wrong.
Nice video , everyone check out my channel and give me a shot (Subscribe) . First video comng soon in my channel so i will appriciate if you check the channel . Thanks
I didn't really see a point in a bridge that was built intentionally to sway from side to side that way. Who in their right mind would walk or drive across something like that?
@YoungMoney4280 : They didn't build it for it to collapse. They built it like any other bridge. they didn't think that it would collapse. Any bridge or road can collapse.
Look at your comment. Back to mine. Back to yours NOW BACK TO MINE. Sadly, it isn't mine. But if you stopped trolling and started posting serious coms it could LOOK like mine. Look down, back up, where are you? You're scrolling through comments, finding the ones that your comment could look like. Back at mine, what is it? It's a highly effective counter-troll. Look again, MY COMMENT NOW HAS MANY THUMBS UP.
Kinda like a truck pulling a trailer in the expressway. Pretend driver correcting right is the wind, and left is gravity. Bad crash will happen when over compensating.
Oh ... oh gods. I wish I had watched this last night instead of tonight, my physics instructor talked about this today and I could have debated if I had seen this earlier ...
I agree that the movement of the bridge is not directly due to resonance due to the wind speed, however resonance is still what causes the bridge to collapse. The aeroelastic flutter converts the wind's constant horizontal speed into a sinusoidal waveform which is what is necessary for resonance of the bridge. The wind causes the flutter and the flutter causes resonance. To say that resonance is not the cause of failure is totally incorrect.
@moomookowz «The wind causes the flutter and the flutter causes resonance.» We know what flutter is (we know its action but its mechanics still remain to be clarified). Explain what you mean by resonance in this context. Please, no epistemological spin so we, students, can finally get it.
@NOYB20100525 Well as far as my understanding goes, the wind is pushing up and down in a cyclic (sinusoidal) manner on the bridge. This is because when the bridge twists, the wind is pushing against a large surface area and therefore creates a large force to twist the bridge back. The speed at which the bridge twists back and forth is the bridge's natural frequency. The increase in size (amplitude) of the twist is due to resonance: each time the bridge twists it twists more and more.
Your teachers are not wrong. The resonance does not have to be caused by an oscillating wind pattern. Do a Fourier analysis on a random but "essentially constant" wind force, and there are nonzero terms in the resonant frequency range. So even an almost constant force can cause resonance.
@merryjman (2/2) not resonance, if air speed is above a critical value called flutter speed (akin to the buckling loads of an axially loaded column). And the small fluctuations you're worried about will act as perturbations (mechanical dither) to make flutter incipient. Interpretation: If things were like you say, there wouldn't be anything left standing.
@merryjman (1/2) These fluctuating components appear randomly in the field and are of unsustained strength. Not significant to drive a structure (only lightly damped, even) to destructive amplitudes at any of its resonant frequencies. Noise (perturbations) in stability parlance. OTOH, the steadiest (non fluctuating) wind achievable in a lab will subject a structure (e.g., a flat elastic plate aligned with flow) to flutter instability,
@SounderBruce One opened in 1950 (the one with the green towers) and the other opened in 2007 (the one with the grey towers). Google the string "en structurae photos index cfm?id=100619" (no quotes) for a nice photo of the twin bridges.
(cont) more precisely the Tacoma bridge collapsed because the amplitude of its oscillation, which frequency is determined by the eigenfrequencies of its torsional modes became too large. That the energy of the wind converted into energy of the resonant frequencies of the bridge is still resonance despite the excitation not being an oscillation, it's just a more complex excitation mechanism.
@MeteorMan05 Eigenfrequencies are frequencies at which a physical system will oscillate on its own. If you take a swing with a certain chain length and weight and shuff it, it will oscillate at a certain frequency. That's the eigenfrequency of the swing. Another way to talk about eigenfrequency is that those are the frequencies at which it will be very good at taking in energy. If you shuff the swing in sync with the eigenfrequency it will swing higher faster. (cont)
@MeteorMan05 (cont) So when I say that the oscillation of a bowed string is dominated by the eigenfrequencies, I mean to indicate that despite the bow motion itself does not particularly induce any frequency at all, the interaction between bow and string will be dominantly driven by the natural (eigen) oscillation frequencies of the string. Incidentally that is why a plucked and a bowed string still play at the same pitch, despite the excitation being drastically different.
@MeteorMan05 Yes, because resonance is not just the response to forced oscillation but is also the oscillation of a system at its own frequency deriving excitation energy from a non-linear mechanism. And more specifically the bridge collapsed because the amplitude of its oscillation at its own resonant frequency became too large.
@socrates856 How did you ascertain the bridge was oscillating at a frequency corresponding to its second (antisymmetric) twisting natural frequency? I agree, a bit too kinky... OK Take 2: Are you aware of any wind tunnel test results in support of your claim? Prof Farquharson did this kind of testing on a small scale (1/200) bridge model. What did he find about the 2nd torsional natural frequency of the mock-up and the observed (lab) flutter frequency of the corresponding "mode"?
@NOYB20100525 I don't fully understand what you are asking, but let me try to carve out what I am saying in context of Bilah and Scanlan's article. I don't disagree with what they are saying at all. The Tacoma collapse is not the consequence of a sinusoidal driving force oscillation and textbooks that do make that case oversimplify things. It is a case of excitation of a torisonal mode (see their section VI). (cont)
@socrates856 (2/2) Despite appearances of obvious truth, you just made the claim «its oscillation at its own resonant frequency». So my question about the frequency of the second natural torsional mode of the bridge (standing wave) vs the observed "frequency" of what appears to be flutter in the same "mode" (travelling wave), question I'm not repeating here.
@NOYB20100525 I would suggest that we talk about this in the context of the last paragraph of Billah and Scanlon before section V. I quote: "Could this be called a resonant phenomenon? It would appear not to contradict the qualitative definition of resonance quoted earlier, if we now identify the source of the periodic impulses as self-induced, the wid supplying the power, and the motion supplying the power-tapping mechanism." I fully agree with the authors here. (cont)
@NOYB20100525 (cont) Observe that the very same effect is at play with bowed strings. The bow provides the energy and impulsive excitation (when it sticks after a slip phase) and the motion of the string provides the power-tapping mechanism. Bowed string excitation is also self-induced in the exact same way. But the point is that the power-tapping is driven by the oscillatory motion coming from the resonant body (bridge, string). (cont)
@NOYB20100525 (cont) now you talk about standing vs traveling waves, and use words in somewhat non-conventional ways. I think to fully discuss the dynamics of the beam is a little tricky given that this is a youtube comment section and not a lecture or seminar, but suffice to say, a traveling wave does by no means preclude resonance, and in fact a "mode" is typically associated with a standing wave phenomenon. (cont)
@NOYB20100525 (cont) what Billah and Scanlon do talk about is discrepancy of frequency to vortex shedding. But vortex shedding indeed is a completely different phenomenon. And I am certainly not arguing that this is the case. All I am saying is that self-induced oscillation is a resonant phenomenon. Not externally forced oscillatory excitation, but still a phenonenon that relies on energy feeding into modes to gain amplitude. The effect is complex and non-linear.
@socrates856 (1/2) For some obscure reason, your comments are a week old but I just read them here for the 1st time. No automatic emails reached my inbox. Strange. And there are signs of positive feedback with one of your comments. Or is it resonance? ;-)
«I don't fully understand what you are asking» In an answer to MeteorMan05, you wrote that «the bridge collapsed because the amplitude of its oscillation at its own resonant frequency became too large».
@NOYB20100525 I don't fully understand what you are asking, but let me try to carve out what I am saying in context of Bilah and Scanlan's article. I don't disagree with what they are saying at all. The Tacoma collapse is not the consequence of a sinusoidal driving force oscillation and textbooks that do make that case oversimplify things. It is a case of excitation of a torisonal mode (see their section VI). (cont)
@NOYB20100525 It seems to me that much of the confusion is the notion of a resonance. The Billah and Scanlan paper is perfectly correct that to state that the Tacoma collapse is not a case of forced external linear resonance. But of course that doesn't mean at all that this isn't resonant behavior of a more complex type. It is in fact clear that the Tacoma bridge was no longer operating in the low amplitude linear domain and collapse itself is not a linear phenomenon. (cont)
@NOYB20100525 It seems to me that much of the confusion is the notion of a resonance. The Billah and Scanlan paper is perfectly correct that to state that the Tacoma collapse is not a case of forced external linear resonance. But of course that doesn't mean at all that this isn't resonant behavior of a more complex type. It is in fact clear that the Tacoma bridge was no longer operating in the low amplitude linear domain and collapse itself is not a linear phenomenon. (cont)
@NOYB20100525 It seems to me that much of the confusion is the notion of a resonance. The Billah and Scanlan paper is perfectly correct to state that the Tacoma collapse is not a case of forced external linear resonance. But of course that doesn't mean at all that this isn't resonant behavior of a more complex type. Already with the bowed string, clearly a different phenomenon, the same holds. The oscillation of a bowed string is not an external linear resonance effect. (cont)
@NOYB20100525 It seems to me that much of the confusion is the notion of a resonance. The Billah and Scanlan paper is perfectly correct to state that the Tacoma collapse is not a case of forced external linear resonance. But of course that doesn't mean at all that this isn't resonant behavior of a more complex type. Already with the bowed string, clearly a different phenomenon, the same holds. The oscillation of a bowed string is not an external linear resonance effect. (cont)
@NOYB20100525 It seems to me that much of the confusion is the notion of a resonance. The Billah and Scanlan paper is perfectly correct to state that the Tacoma collapse is not a case of forced external linear resonance. But of course that doesn't mean at all that this isn't resonant behavior of a more complex type. Already with the bowed string, clearly a different phenomenon, the same holds. The oscillation of a bowed string is not an external linear resonance effect. (cont)
Frankly I think the presentation here is misleading. The bridge did collapse because of resonance, just not by forced oscillatory excitation. Phenoma like this are well-known such as the use of a violin bow to excite a string. The sound of the string is dominated by the eigenfrequencies (resonant frequencies) of the string despite the main direction of the bow being non-oscillatory. A non-linear slip-stick mechanism is responsible for the conversion. But it's still resonance. (cont)
I've been told a dozen times that Tacoma Narrows was due to resonance throughout uni, and a couple of times in Fluids lectures that vortex shedding was a major influence. For such an overused example, why is there not a clear consensus?
@JaySmith91 Because people didn't read the final report of the enquiry? Or the research reports made by Prof Farquharson (the guy smoking a pipe in the vid) in the 1940's and 1950's?
"...this was enough to keep the bridge oscillating with a period of 5 seconds."
It was oscillating with a period of 5 seconds, therefore, a resonant frequency (OF THE ENTIRE SYSTEM) had been reached. So, while you are correct that the initial phenomena was caused by aeroelastic flutter, it DID reach a resonant frequency.
but that means ghosts are not real! that means my teacher is a lyer!!!!!!! she says there is a ghost in our room and if you steal something it will tell her. SHE LIES!!!!!!!!!!!!!
i don't get this. At the start you said it had nothing todo with resonance Wind but the end of the video it had something todo with the wind? I'm starting to think you make shit up sometimes unless someone can explain it to me
@xSandman16x You understand how lift is generated on an airplane wing? [If you don't, go to Wikipedia and search for "lift (force)" and on the wiki page look for the section "Pressure differences". About the same thing happens below and above the bridge deck, except the deck is more flexible in torsion than a wing.] Google "vibrationdata" (one word) and the 1st result will have a sub-header called Tacoma Narrows Bridge Failure. Scroll down to Aerodynamic Instability. There you are.
@xSandman16x (4/4) This wind torque (action) will be balanced (equilibrium) by an equal but opposite torque (reaction) at the deck-tower junctions where the deck is attached to the towers. When this wind torque becomes larger than the maximum achievable resisting torque at the junctions (the fluid-structure interaction is continuously pumping energy into the system, stored in the vibrations), the attachments will break.
@xSandman16x (3/4) This front-rear wind force difference is equivalent to a torque applied to the deck (force x lever arm; see your physics/statics text) . The action of this wind torque is to _increase_ the pitch (slant) of the deck. Remember, the force at the leading edge (front) is larger and is pushing on the deck, so its action is to increase the pitch angle.
@xSandman16x (2/4) From your reading of this wiki page about lift (pressure differences), you learned that the pressure _difference_ (pressure below deck minus pressure above deck) along the pitching (slanting) deck is always higher at the leading edge (front) than at the trailing edge (rear). If pressure differences at the front and at the rear don't even out completely, so do forces at the front and the rear (pressure = force per unit area).
@xSandman16x (1/4) Exactly what I meant too. You don't ask when the front half is up and the back half is down... so you understand that both positions (mirror positions with respect to the horizontal) have identical force distributions, no matter if the wind is pushing from above or from below the deck (sketches). Cambered wing or pitching deck, roughly the same principles hold.
To lie: To present false information with the intention of deceiving.
Teachers are just passing on the information they have to us. Their information may not be always accurate but they don't willfully lie to us. The problem is often with their primary source(s) of information... Textbooks! For this reason, these large classrooms called Wikipedia and YT are worth visiting from time to time as you now know.
@BlazingBobby I am not trying to argue but only trying to get the facts straight, I tried to clarify the actual cause of the collapse and during this process I checked wikipedia where they explain that it is in fact due to aeroelastic fluttering and wrongly assumed to be mechanical resonance, but its still kind of in debate between different scientists/engineers. My main point being you cannot be 100% sure and minutephysics has a fair amount of facts right.
vortex shitting?
hogwashsentinel 1 day ago
wow that was the exact example told in my college to explain resonance and i had that same thought of " how does a constant wind-blow cause resonance? " .. thanks for clearing this up
abcas1990 5 days ago in playlist MinutePhysics
At the end of the day WIND still caused it
kikook222 1 week ago
Tell that to my engineering proffs.
allyhaw 1 week ago
@allyhaw Emails?
tabaks 1 week ago
physics just blew ghosts away!
SophieHatterLeFay 1 week ago
dam u minutephysics
-sincerely,
ghosts
jlmknight 1 week ago 2
Hmm, I don't think that this video helps anyone by saying it strictly wasn't resonance.
The article quoted in the description makes the distinction between forced resonance and self-excitation. Not so much that this wasn't a case of resonance between the period of the bridge displacement and the force input, but rather that the two periods were intrinsically linked (force on the bridge depended on the bridge position). This combined with insufficient dampening in the system resulted in failure.
MicroCrayonSaw 1 week ago 14
this is wrong, aeroelastic flutter happens because of both vortex shedding and resonance. you cant have movement without a force
powwow151 1 week ago in playlist MinutePhysics
@powwow151 i know right, its so sad when people make videos of false "physics" then everyone gets on youtube and eats it up as truth
ExtemelyStoopid 1 week ago in playlist MinutePhysics 2
@ExtemelyStoopid instead of just craping on this video posters comment section with negative attitudes how about you post links and videos that prove it wrong or show what aeroelastic flutter really is and what causes it. You think anyone is going to take what you said as true over the video of the one minute physics guy. No and if you are going to laugh at people trying to learn something in a fun and creative way then you have no right commenting here at all.Good day sir.
MrSumbody69 1 week ago
@MrSumbody69 You couldn't be more incorrect. Your attitude is exactly the attitude that ruins Youtube comment sections. He didn't claim anything that he needed to prove. Moreover, learning in a fun and creative way is fantastic, but using a medium such as the internet means you have the ability to learn things wrong. You have to appreciate that that might be the case and thank people when they are willing to stand up and say so. It's for your benefit.
jkennedy561 1 week ago
@jkennedy561 Dude, by repeating arguments, you aren't really making any progress nor do you sound any smarter.
tabaks 1 week ago
@tabaks I don't aim to sound smart; if that were life's aim, life would be very pointless. I'm merely saying that you can't believe everything you watch. I think that was what is being got at here. I made my opinion on the video quite clear a few comments before, so I didn't bother writing it again. Sorry if I sound like I'm trying to be a know-it-all, I just really fear for people who don't question the content they watch.
jkennedy561 1 week ago
@ExtemelyStoopid Yes, you are.
tabaks 1 week ago
Very smart. Thanks for these series of videos. they're FANTASTIC! :D
EnrichedPlutonium 1 week ago in playlist MinutePhysics
I have Physics in high school, and after all these videos, I only understand resonance COMPLETELY.
talentra2709 2 weeks ago
I must show my physics teacher this XD
musicismylife816 2 weeks ago
BOOM that's Physics for ya ghosts!
Dam ghosts making up rumors and crap like that.
porecore101Second 2 weeks ago in playlist MinutePhysics
So, resonance was supposed to be the reason soldiers fall out and march at random when crossing a bridge, . . . is that pointless under this analysis? Can we prevent aeroelastic flutter?
mickeymcomber 2 weeks ago
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It may not be externally induced resonance, but it's resonance none-the-less (self-induced resonance). This video is doing the same as the textbooks by over-simplifying the physics. It is still an absolutely valid example of resonance for teachers to use and for pupils to remember.
jkennedy561 2 weeks ago
Comment removed
jkennedy561 2 weeks ago
*clicks on a minutephysics video*..."people its time to tab - " * clicks on nother video*.. "people it's time to t-" FUUUUUUUUUUUUUUUUUUUUUUUU
hairyriceballs 2 weeks ago
This video is all about splitting hairs to force false originality. The flutter is the CAUSE of the resonance effect. There is no new information here.
skadar 3 weeks ago
@skadar To be fair, I've read articles and have heard people say that it was because the canyons were just right for the wind to blow in pulses, so some people out there are wrong.
DKM101 2 weeks ago
My home town! Seattle!:)
VlogTanner 3 weeks ago
i love how science can rape religon and any other brain washed spiritual freaks :)
vMicahs 3 weeks ago in playlist MinutePhysics
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Nice video , everyone check out my channel and give me a shot (Subscribe) . First video comng soon in my channel so i will appriciate if you check the channel . Thanks
MrFunnyPhysics 3 weeks ago in playlist MinutePhysics
I didn't really see a point in a bridge that was built intentionally to sway from side to side that way. Who in their right mind would walk or drive across something like that?
YoungMoney4280 3 weeks ago
@YoungMoney4280 : They didn't build it for it to collapse. They built it like any other bridge. they didn't think that it would collapse. Any bridge or road can collapse.
pinkflamango94 2 weeks ago
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@pinkflamango94 Yep.
YoungMoney4280 2 weeks ago
This has been flagged as spam show
Look at your comment. Back to mine. Back to yours NOW BACK TO MINE. Sadly, it isn't mine. But if you stopped trolling and started posting serious coms it could LOOK like mine. Look down, back up, where are you? You're scrolling through comments, finding the ones that your comment could look like. Back at mine, what is it? It's a highly effective counter-troll. Look again, MY COMMENT NOW HAS MANY THUMBS UP.
Anything is possible when you copy and paste.
I'm on a Laptop
Itaimumwiroikm 3 weeks ago in playlist MinutePhysics
Your videos are amazing. Subscribed.
AndrewDangerously 3 weeks ago in playlist MinutePhysics
Kinda like a truck pulling a trailer in the expressway. Pretend driver correcting right is the wind, and left is gravity. Bad crash will happen when over compensating.
TheLighto0 3 weeks ago
my teacher just doesn't believe me :(
noobcastle 3 weeks ago
running out of ink......
Ramboost007 4 weeks ago
is aeroelastic flutter the same as bernoulli's principle?
lion95805 4 weeks ago in playlist MinutePhysics
were and what specifically do u teach? i want to take your class!
iamwhitelivewithit 1 month ago in playlist MinutePhysics
Artist, comedian, ghost story debunker. BEST TEACHER EVER
icanfinallybreathe 1 month ago in playlist MinutePhysics
So momentarily the bridge get more energy spontaneously until breake? Like infinite and increasing energy?
HugoBDesigner 1 month ago in playlist Mais vídeos de minutephysics
Oh ... oh gods. I wish I had watched this last night instead of tonight, my physics instructor talked about this today and I could have debated if I had seen this earlier ...
DarthFennec 1 month ago in playlist More videos from minutephysics
also known as torsion, correct?
bluejames1998 1 month ago in playlist MinutePhysics 25
@bluejames1998 No.
tabaks 1 week ago
I just emailed my physics teacher to tell him he's wrong. You think you can get credit on a test you took years ago.
colebarclay 1 month ago in playlist MinutePhysics
...welp. resonance still broke the bridge. you just went into greater detail of what caused the resonance
Shmior 1 month ago in playlist MinutePhysics
And now I can never fly again.
alexandergifford 1 month ago in playlist More videos from minutephysics
How did the bridge start moving in the first place?
PotterSuccess 1 month ago
@PotterSuccess I`m guessing that the wind was somehow not paralell to the ground or smth like that XD
Or there were more cars on one side of the bridge than on the other and the bridge tilted a tiny bit, which started the fluttering.
TheJorens 1 month ago
@PotterSuccess The constant wind speeds twisted it.
SoulJestic 1 month ago in playlist More videos from minutephysics
NOW, there are two tacoma narrows bridges :) rode on them a few weeks back :)
danieldawson97135 1 month ago
so we need to make bridges and planes more Fluttershy?
ikanhazw1n 1 month ago
my physics teacher showed my class the tacoma bridge falling like two days before i watched this! i wish i had seen this video first!
goaliez95 1 month ago
The faster this guy talks, the sooner he keeps talking.
YentaY0 1 month ago
My teacher says it is resonance. I'll show him this vid. =P
iRaHaKaZ 1 month ago in playlist MinutePhysics
Im studying for a chemstry exam tomorrow yet im watching this.
McDADDyK 1 month ago in playlist MinutePhysics
i think if i had you as my teacher i actually would have stayed awake in class
lpfan540 1 month ago in playlist MinutePhysics
I wasn't told it was resonance :/ but resonance is cool.... Just ask Tesla XD
Storm13Cloud 1 month ago in playlist MinutePhysics
What if this incident was a combination of both aeroelastic flutter and resonance?
APPLESNACKPATEL 1 month ago
It's true. Over here we refer to the collapse as FAIL.
MadeOfCATS 1 month ago in playlist MinutePhysics
I agree that the movement of the bridge is not directly due to resonance due to the wind speed, however resonance is still what causes the bridge to collapse. The aeroelastic flutter converts the wind's constant horizontal speed into a sinusoidal waveform which is what is necessary for resonance of the bridge. The wind causes the flutter and the flutter causes resonance. To say that resonance is not the cause of failure is totally incorrect.
moomookowz 1 month ago
@moomookowz «The wind causes the flutter and the flutter causes resonance.» We know what flutter is (we know its action but its mechanics still remain to be clarified). Explain what you mean by resonance in this context. Please, no epistemological spin so we, students, can finally get it.
NOYB20100525 1 month ago
@NOYB20100525 Well as far as my understanding goes, the wind is pushing up and down in a cyclic (sinusoidal) manner on the bridge. This is because when the bridge twists, the wind is pushing against a large surface area and therefore creates a large force to twist the bridge back. The speed at which the bridge twists back and forth is the bridge's natural frequency. The increase in size (amplitude) of the twist is due to resonance: each time the bridge twists it twists more and more.
moomookowz 1 month ago
Poor ghosts... :(
Piemasta9000 1 month ago in playlist MinutePhysics 53
Your teachers are not wrong. The resonance does not have to be caused by an oscillating wind pattern. Do a Fourier analysis on a random but "essentially constant" wind force, and there are nonzero terms in the resonant frequency range. So even an almost constant force can cause resonance.
merryjman 1 month ago
@merryjman (2/2) not resonance, if air speed is above a critical value called flutter speed (akin to the buckling loads of an axially loaded column). And the small fluctuations you're worried about will act as perturbations (mechanical dither) to make flutter incipient. Interpretation: If things were like you say, there wouldn't be anything left standing.
NOYB20100525 1 month ago
@merryjman (1/2) These fluctuating components appear randomly in the field and are of unsustained strength. Not significant to drive a structure (only lightly damped, even) to destructive amplitudes at any of its resonant frequencies. Noise (perturbations) in stability parlance. OTOH, the steadiest (non fluctuating) wind achievable in a lab will subject a structure (e.g., a flat elastic plate aligned with flow) to flutter instability,
NOYB20100525 1 month ago
"Sorry ghosts physics just blew you away" ...
Awesome :)
SuperBeetah 1 month ago
Everyday I'm bufferin'
OLH064 1 month ago
ill never more fly in a airplane!
galicory 1 month ago
@galicory After watching this video I guess... v=iTFZNrTYp3k
NOYB20100525 1 month ago
Time to get a new marker!
jeeigoe 1 month ago in playlist MinutePhysics
lolss can you be my physics teacher?
CaseyYi914522 1 month ago in playlist MinutePhysics
I live next to the new bridges. They built 2 bridges.
SounderBruce 1 month ago
@SounderBruce One opened in 1950 (the one with the green towers) and the other opened in 2007 (the one with the grey towers). Google the string "en structurae photos index cfm?id=100619" (no quotes) for a nice photo of the twin bridges.
NOYB20100525 1 month ago
... where is a video of this "haunted' swing!? must seeeeee
scifigeek14 1 month ago in playlist MinutePhysics
@scifigeek14 v=0xtj4ztue-o Watch it to the end.
NOYB20100525 1 month ago
Wow, I just learned that! And yes, my teacher was wrong... lol
YellowFranification 1 month ago in playlist More videos from minutephysics
GO PHYSICS !!! <3
1lagarti 1 month ago in playlist MinutePhysics
oh cool, something i know about!
so...my teacher was wrong? wow, go physics
CondorK92 1 month ago in playlist More videos from minutephysics
i want you to be my teacher
mrluke25041 1 month ago in playlist MinutePhysics 73
my teacher made 38 accounts and disliked this video.
canadianeqator 2 months ago
If I remember it correctly, Mythbusters did an episode about resonance and the Tacoma Narrows Bridge
devilsadvocate22289 2 months ago in playlist MinutePhysics
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w1c1f2 2 months ago
my smarticles are now filled with knowledge
DONTjackMYtaco 2 months ago
(cont) more precisely the Tacoma bridge collapsed because the amplitude of its oscillation, which frequency is determined by the eigenfrequencies of its torsional modes became too large. That the energy of the wind converted into energy of the resonant frequencies of the bridge is still resonance despite the excitation not being an oscillation, it's just a more complex excitation mechanism.
socrates856 2 months ago in playlist MinutePhysics 15
@socrates856 Whoa whoa whoa, explain yourself further. You just disputed the author of the video's claim that is wasn't resonance. Explain, please.
MeteorMan05 1 month ago
@MeteorMan05 What part of my explanation is unclear to you? I'll do my best to fill in.
socrates856 1 month ago
@socrates856 What MeteorMan05 didn't get is your «_dominated_ by the eigenfrequencies (resonant frequencies)» (emphasis mine).
NOYB20100525 1 month ago
@socrates856 Yeah, eigenfrequencies? I find myself misunderstanding.
MeteorMan05 1 month ago
@MeteorMan05 Eigenfrequencies are frequencies at which a physical system will oscillate on its own. If you take a swing with a certain chain length and weight and shuff it, it will oscillate at a certain frequency. That's the eigenfrequency of the swing. Another way to talk about eigenfrequency is that those are the frequencies at which it will be very good at taking in energy. If you shuff the swing in sync with the eigenfrequency it will swing higher faster. (cont)
socrates856 1 month ago
@MeteorMan05 (cont) So when I say that the oscillation of a bowed string is dominated by the eigenfrequencies, I mean to indicate that despite the bow motion itself does not particularly induce any frequency at all, the interaction between bow and string will be dominantly driven by the natural (eigen) oscillation frequencies of the string. Incidentally that is why a plucked and a bowed string still play at the same pitch, despite the excitation being drastically different.
socrates856 1 month ago
@socrates856 Ahh I see. So back to the question at hand, was the collapse of the Tacoma narrows bride due to resonance?
MeteorMan05 1 month ago
@MeteorMan05 Yes, because resonance is not just the response to forced oscillation but is also the oscillation of a system at its own frequency deriving excitation energy from a non-linear mechanism. And more specifically the bridge collapsed because the amplitude of its oscillation at its own resonant frequency became too large.
socrates856 1 month ago
@socrates856 How did you ascertain the bridge was oscillating at a frequency corresponding to its second (antisymmetric) twisting natural frequency? I agree, a bit too kinky... OK Take 2: Are you aware of any wind tunnel test results in support of your claim? Prof Farquharson did this kind of testing on a small scale (1/200) bridge model. What did he find about the 2nd torsional natural frequency of the mock-up and the observed (lab) flutter frequency of the corresponding "mode"?
NOYB20100525 1 month ago
@NOYB20100525 In the last sentence of my previous comment, «(lab) flutter frequency of» should read «(lab) flutter "frequency" of».
NOYB20100525 1 month ago
@NOYB20100525 I don't fully understand what you are asking, but let me try to carve out what I am saying in context of Bilah and Scanlan's article. I don't disagree with what they are saying at all. The Tacoma collapse is not the consequence of a sinusoidal driving force oscillation and textbooks that do make that case oversimplify things. It is a case of excitation of a torisonal mode (see their section VI). (cont)
socrates856 1 month ago
@socrates856 (2/2) Despite appearances of obvious truth, you just made the claim «its oscillation at its own resonant frequency». So my question about the frequency of the second natural torsional mode of the bridge (standing wave) vs the observed "frequency" of what appears to be flutter in the same "mode" (travelling wave), question I'm not repeating here.
NOYB20100525 1 month ago
@NOYB20100525 I would suggest that we talk about this in the context of the last paragraph of Billah and Scanlon before section V. I quote: "Could this be called a resonant phenomenon? It would appear not to contradict the qualitative definition of resonance quoted earlier, if we now identify the source of the periodic impulses as self-induced, the wid supplying the power, and the motion supplying the power-tapping mechanism." I fully agree with the authors here. (cont)
socrates856 1 month ago
@NOYB20100525 (cont) Observe that the very same effect is at play with bowed strings. The bow provides the energy and impulsive excitation (when it sticks after a slip phase) and the motion of the string provides the power-tapping mechanism. Bowed string excitation is also self-induced in the exact same way. But the point is that the power-tapping is driven by the oscillatory motion coming from the resonant body (bridge, string). (cont)
socrates856 1 month ago
@NOYB20100525 (cont) now you talk about standing vs traveling waves, and use words in somewhat non-conventional ways. I think to fully discuss the dynamics of the beam is a little tricky given that this is a youtube comment section and not a lecture or seminar, but suffice to say, a traveling wave does by no means preclude resonance, and in fact a "mode" is typically associated with a standing wave phenomenon. (cont)
socrates856 1 month ago
@NOYB20100525 (cont) what Billah and Scanlon do talk about is discrepancy of frequency to vortex shedding. But vortex shedding indeed is a completely different phenomenon. And I am certainly not arguing that this is the case. All I am saying is that self-induced oscillation is a resonant phenomenon. Not externally forced oscillatory excitation, but still a phenonenon that relies on energy feeding into modes to gain amplitude. The effect is complex and non-linear.
socrates856 1 month ago
@socrates856 (1/2) For some obscure reason, your comments are a week old but I just read them here for the 1st time. No automatic emails reached my inbox. Strange. And there are signs of positive feedback with one of your comments. Or is it resonance? ;-)
«I don't fully understand what you are asking» In an answer to MeteorMan05, you wrote that «the bridge collapsed because the amplitude of its oscillation at its own resonant frequency became too large».
NOYB20100525 1 month ago
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@NOYB20100525 I don't fully understand what you are asking, but let me try to carve out what I am saying in context of Bilah and Scanlan's article. I don't disagree with what they are saying at all. The Tacoma collapse is not the consequence of a sinusoidal driving force oscillation and textbooks that do make that case oversimplify things. It is a case of excitation of a torisonal mode (see their section VI). (cont)
socrates856 1 month ago
@NOYB20100525 It seems to me that much of the confusion is the notion of a resonance. The Billah and Scanlan paper is perfectly correct that to state that the Tacoma collapse is not a case of forced external linear resonance. But of course that doesn't mean at all that this isn't resonant behavior of a more complex type. It is in fact clear that the Tacoma bridge was no longer operating in the low amplitude linear domain and collapse itself is not a linear phenomenon. (cont)
socrates856 1 month ago
@NOYB20100525 It seems to me that much of the confusion is the notion of a resonance. The Billah and Scanlan paper is perfectly correct that to state that the Tacoma collapse is not a case of forced external linear resonance. But of course that doesn't mean at all that this isn't resonant behavior of a more complex type. It is in fact clear that the Tacoma bridge was no longer operating in the low amplitude linear domain and collapse itself is not a linear phenomenon. (cont)
socrates856 1 month ago
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@NOYB20100525 It seems to me that much of the confusion is the notion of a resonance. The Billah and Scanlan paper is perfectly correct to state that the Tacoma collapse is not a case of forced external linear resonance. But of course that doesn't mean at all that this isn't resonant behavior of a more complex type. Already with the bowed string, clearly a different phenomenon, the same holds. The oscillation of a bowed string is not an external linear resonance effect. (cont)
socrates856 1 month ago
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@NOYB20100525 It seems to me that much of the confusion is the notion of a resonance. The Billah and Scanlan paper is perfectly correct to state that the Tacoma collapse is not a case of forced external linear resonance. But of course that doesn't mean at all that this isn't resonant behavior of a more complex type. Already with the bowed string, clearly a different phenomenon, the same holds. The oscillation of a bowed string is not an external linear resonance effect. (cont)
socrates856 1 month ago
@NOYB20100525 It seems to me that much of the confusion is the notion of a resonance. The Billah and Scanlan paper is perfectly correct to state that the Tacoma collapse is not a case of forced external linear resonance. But of course that doesn't mean at all that this isn't resonant behavior of a more complex type. Already with the bowed string, clearly a different phenomenon, the same holds. The oscillation of a bowed string is not an external linear resonance effect. (cont)
socrates856 1 month ago
@socrates856 Now with string bass in the background?
miauw62 1 month ago
Frankly I think the presentation here is misleading. The bridge did collapse because of resonance, just not by forced oscillatory excitation. Phenoma like this are well-known such as the use of a violin bow to excite a string. The sound of the string is dominated by the eigenfrequencies (resonant frequencies) of the string despite the main direction of the bow being non-oscillatory. A non-linear slip-stick mechanism is responsible for the conversion. But it's still resonance. (cont)
socrates856 2 months ago in playlist MinutePhysics 3
That awkward moment you ask your Physics teacher what caused the collapse of the Tacoma Narrows bridge and they say "aeroelastic flutter."
Awesomeexplosivecool 2 months ago in playlist MinutePhysics 3
I've been told a dozen times that Tacoma Narrows was due to resonance throughout uni, and a couple of times in Fluids lectures that vortex shedding was a major influence. For such an overused example, why is there not a clear consensus?
JaySmith91 2 months ago in playlist MinutePhysics
@JaySmith91 Because people didn't read the final report of the enquiry? Or the research reports made by Prof Farquharson (the guy smoking a pipe in the vid) in the 1940's and 1950's?
NOYB20100525 1 month ago
btw in seattle they say its aeroelastic flutter..... at least in my school.
ceyel6 2 months ago
This guy is amazing!
K00KieM0nst3R 2 months ago in playlist MinutePhysics
im a 6th garade physiscs
pester39 2 months ago in playlist MinutePhysics
Nurd rage is for chemistry Vasuce is for fun facts and minutephysics is for physics together they form the only thing that keeps the internet smart
mrhinslh 2 months ago
@mrhinslh and vlogbrothers are for decreasing world suck...
sciencenerd111 2 months ago in playlist MinutePhysics
NO I FINISHED ALL HIS VIDEOS!!! WHAT DO I DO NOW????
yurishosan 2 months ago in playlist More videos from minutephysics
@yurishosan Watch next weeks video, then the next, etc.
faillblogkeyboardcat 2 months ago in playlist MinutePhysics
@faillblogkeyboardcat I can't wait...
yurishosan 2 months ago
@yurishosan Watch Vsauce!
TheMonstermike3 2 months ago
@TheMonstermike3 already do!
yurishosan 2 months ago
Well. if it happened in the 1960s, and the law of probability states that it will happen again, doesnt that mean one will happen soon? D:
undeadgamer95 2 months ago in playlist MinutePhysics
The video you link to:
"...this was enough to keep the bridge oscillating with a period of 5 seconds."
It was oscillating with a period of 5 seconds, therefore, a resonant frequency (OF THE ENTIRE SYSTEM) had been reached. So, while you are correct that the initial phenomena was caused by aeroelastic flutter, it DID reach a resonant frequency.
ThinkTank255 2 months ago
but that means ghosts are not real! that means my teacher is a lyer!!!!!!! she says there is a ghost in our room and if you steal something it will tell her. SHE LIES!!!!!!!!!!!!!
wikkyz4903 2 months ago in playlist MinutePhysics
i don't get this. At the start you said it had nothing todo with resonance Wind but the end of the video it had something todo with the wind? I'm starting to think you make shit up sometimes unless someone can explain it to me
Cookiez255 2 months ago in playlist MinutePhysics
Aeroelastic flutter is still a resonant phenomenon, no?
HiAdrian 2 months ago
Physics <3
est101010 2 months ago in playlist More videos from minutephysics
Can you explain how my office chair can turn without stopping even when i'm sitting still in it? I've seen other chairs that do it too. Its weird!
joemonster55 2 months ago in playlist MinutePhysics
@joemonster55 it stops eventually
StrykeEvil 2 months ago
The puns!
frag971 2 months ago
@funnygirl650 o: don't let that stop you! tell them anyway! be the coolest 11 year old of the day! :)
rememberxjuly 2 months ago in playlist MinutePhysics
I stumped my teacher with this thanks :D
The64Atom 2 months ago 3
come be my teacher, make science and maths fun again :)
Gridlockdmusic 2 months ago 3
I have to show this to my teacher now :L
scampynoXP 2 months ago in playlist More videos from minutephysics 3
Sorry ghosts. Physics just blew you away. Lol
klilo98 2 months ago
i feel smarter for watching this.
TPeters321 2 months ago 59
I just want my teacher to tell me that it was because of resonance, so I can be like, IT WAS AEROELASTIC FLUTTER YOU STUPID BITCH
SnapCrackleJared 2 months ago 168
@SnapCrackleJared XD
MrKillJoy200 1 month ago
Same basic thing with speed wobbles on a skateboard. Yay science!
GageMassoli 2 months ago
But if the wind could push the bridge down in the front, isn't it also pushing the bridge on the other side down to even it off?
xSandman16x 2 months ago in playlist MinutePhysics
@xSandman16x You understand how lift is generated on an airplane wing? [If you don't, go to Wikipedia and search for "lift (force)" and on the wiki page look for the section "Pressure differences". About the same thing happens below and above the bridge deck, except the deck is more flexible in torsion than a wing.] Google "vibrationdata" (one word) and the 1st result will have a sub-header called Tacoma Narrows Bridge Failure. Scroll down to Aerodynamic Instability. There you are.
NOYB20100525 2 months ago
@NOYB20100525 I don't mean while it's flat, i mean once it has bent down in front and the back half is elevated
xSandman16x 2 months ago
@xSandman16x (4/4) This wind torque (action) will be balanced (equilibrium) by an equal but opposite torque (reaction) at the deck-tower junctions where the deck is attached to the towers. When this wind torque becomes larger than the maximum achievable resisting torque at the junctions (the fluid-structure interaction is continuously pumping energy into the system, stored in the vibrations), the attachments will break.
NOYB20100525 2 months ago
@xSandman16x (3/4) This front-rear wind force difference is equivalent to a torque applied to the deck (force x lever arm; see your physics/statics text) . The action of this wind torque is to _increase_ the pitch (slant) of the deck. Remember, the force at the leading edge (front) is larger and is pushing on the deck, so its action is to increase the pitch angle.
NOYB20100525 2 months ago
@xSandman16x (2/4) From your reading of this wiki page about lift (pressure differences), you learned that the pressure _difference_ (pressure below deck minus pressure above deck) along the pitching (slanting) deck is always higher at the leading edge (front) than at the trailing edge (rear). If pressure differences at the front and at the rear don't even out completely, so do forces at the front and the rear (pressure = force per unit area).
NOYB20100525 2 months ago
@xSandman16x (1/4) Exactly what I meant too. You don't ask when the front half is up and the back half is down... so you understand that both positions (mirror positions with respect to the horizontal) have identical force distributions, no matter if the wind is pushing from above or from below the deck (sketches). Cambered wing or pitching deck, roughly the same principles hold.
NOYB20100525 2 months ago
our mechanics lecturers have lied to us!
hito2hito 2 months ago
@hito2hito
To lie: To present false information with the intention of deceiving.
Teachers are just passing on the information they have to us. Their information may not be always accurate but they don't willfully lie to us. The problem is often with their primary source(s) of information... Textbooks! For this reason, these large classrooms called Wikipedia and YT are worth visiting from time to time as you now know.
NOYB20100525 2 months ago
so it was the wind..just not the way teachers thought right? wtf
pootytang82 2 months ago
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MultiAhka 2 months ago
Physics just blew away ghosts!
TheDocfazz 2 months ago
@TheDocfazz My god people are so stupid these days.
SMFApples 2 months ago
Damn!!! physics... you scary!
Comorasu 2 months ago in playlist MinutePhysics
what do you say about argentina?
Ramix09 2 months ago
what? its still resonance, your just being podantic
Nathanchooper 2 months ago
@Nathanchooper
Science requires language that is both precise and accurate. Pedantic notwithstanding, you have to be correct.
Heresy488 2 months ago
look at all these people trying to look smart by over replying you know they just goggled it....
harold123sk8 2 months ago
@BlazingBobby I am not trying to argue but only trying to get the facts straight, I tried to clarify the actual cause of the collapse and during this process I checked wikipedia where they explain that it is in fact due to aeroelastic fluttering and wrongly assumed to be mechanical resonance, but its still kind of in debate between different scientists/engineers. My main point being you cannot be 100% sure and minutephysics has a fair amount of facts right.
mysterymandoll 2 months ago in playlist MinutePhysics
but wouldn't the wind be the fuel or help the aeroelastic flutter?
phantomrider115 2 months ago in playlist MinutePhysics
!!!VSAUCE!!!
96kazyamamoto 2 months ago
THIS VIDEO IS ALMOST 2 MINUTES!!
finalawesome 2 months ago
Those ghosts are so cute XD
worldwidewackyness 2 months ago in playlist MinutePhysics
TAKE THAT GHOSTZ
Legendhalfliferrr 2 months ago 2
your all wrong it was the moth man
MrMustacheman69 2 months ago 3
i dont understand but i still like their vids
hotshot32ful 2 months ago in playlist MinutePhysics