Dr Lewin. You are the most intelligent human I have ever seen. I am from India and am preparing for GATE 2020. Thats a test of engineerimg graduates. In the moments I feel low, demotivated I watch your videos. They inspire me a lot. Thank You for Everything. Love You Sir.
Amazing experiment sir i have seen 1,2and 3rd harmonic in mechanical wave experiment with heavy chain 🔗 but listened to it 1st time in my life. Thank sir. 🙏🙏🙏🙏🙏
Absolutely awesome. I know a lot about music theory and how the overtones are generated, but I learned a lot here about how the tube generates it's fundamental frequency when passing air over one end! And it's amazing how just by swirling it faster (passing the air faster?) you get the higher harmonics!
Sir , India probably is your largest fan base. We heartly welcomes you here. Considering how love from India for professor is tremendous, I believe you should have tried coming to India frequently. Probably if you would have done so , you can count and miss every single visit here.
Sir don’t get disappointed by seeing the number of views....these months are very crucial time for jee aspirants...in India...So ....love physics !!love you sir!!!
PSS X Thats not something that reduces the views..Even I’m a jee aspirant. These problems genuinely help me and i do hope that he doesnt stop making these
Aniket Pai but few parents or....some one stop them from watching these right. ?just to concentrate .........iam damn sure that’s how ever watches these ...they are interested in physics.........and as always love physics!,!
To find the fundamental frequency we can use the formula f=V/(2L) since it’s an open/open pipe. V=the speed of sound which depends on the temperature but I will assume it is 20°C To find the speed we use the formula: 331+0.6T 331+0.6•20=343m/s Now we plug this into the original formula: 343/(2•0.76meters)=226Hz approximately. To find other harmonics we simply multiply the answer by 2 and 3 451Hz 677Hz
Dir Lewin, I've seen almost all of your videos their are the most knowledgeable and fun way to learn, waiting for new ones. I'll do anything in order to meet you even for 5 minutes. Looking forward to meeting you.
Sir, I am from India. currently in the final year of my bachelor's degree in Physics. First, I would mention (as I also have a drop of knowledge from the ocean of music!) that the second note that was generated was not an octave up but was the fifth up note of the first note i.e. the fundamental note. Coming to the problem, we know that the fundamental freq. (let it be F0) in an Open-Open pipe is given by f0=v/2L where, F0 is the fundamental frequency; v is the velocity of sound in air and L is the length of the pipe used. As you say and I trust you that the length of the pipe is 76cm=0.76m and the velocity is known to us to be 346m/sec. when we substitute these values in the equation of the F0, we get f0=227.63Hz. And the succeeding harmonics (except 1st Harmonic) will be the integral multiples of F0. i.e. F1=227.63 F2=455.26 and so on. The reason why F0=F1 is because that the pipe is open at both the ends.
What you were saying was the fundamental wasn’t the fundamental though, it was the first harmonic. Because the next harmonic up was a fifth higher, not an octave
I accept your judgement - students at MIT have also mentioned this to me. Please send me the frequencies of the 3 resonances that I excited. When I give the solutions, I will give you credit.
I went down the comments to see if someone had written about that already. The first harmonic has twice the frequency of the fundamental, that is, a full octave. The "first" harmonic in the video sounds a fifth above the "fundamental", therefore we can conclude the "fundamental" was actually the first harmonic and we really never heard the fundamental. It still amazes me that our brain is capable of doing the equivalent of Fourier's transform and recognize the different frequencies. Players of brass instruments are very aware of this, as it is the principle of the instrument and, especially for horn players, we have warm up exercises going through the harmonics in all tubes combinations. Still, this is a very interesting exercise thank you, Walter :) now I'll watch your lectures on the topic ;)
Simple model for open open tube yield a spectrum of frequencies for each natural number n given by: f=n*v/(2L) where v is speed of sound and L is length of tube Using v=340m/s and L=0.76m, we get about f=n*224 hz Thus the fundamental is 224 hz, the first harmonic is 448 hz, the second harmonic is 672 hz, the third harmonic is 896 hz In the experiment you performed, the notes sounded close to Aflat4, Eflat5, and Aflat5, which has frequencies of about 415.3 hz, 622.3 hz, 830.6 hz (standard equal temperament A4=440 hz tuning) These are reasonably close to the calculated values for the first, second, and third harmonic respectively, and the pattern lines up with those harmonics (a perfect fifth then a perfect fourth). Thus the actual fundamental if you could excite it would probably be close to Aflat3=207.7 The error between 207.7 and 224 is likely due to variation in speed of sound and end effects not taken into account in the simple model.
"The fundamental and harmonics of a corrugated tube are lower than those of an uncorrugated tube of the same length and diameter" "The difference in speed between the moving end of the tube and the stationary, hand-held end creates a difference in air pressure. A higher pressure is at the fixed end and a lower pressure is at the moving end." en.wikipedia.org/wiki/Whirly_tube
Sorry to be a party pooper here. What I heard was an A flat, the low tone; E flat, the middle tone; and A flat the Hi-Tone. What I'm calling the low tone sounded an octave below the high tone and the middle tone was a perfect fifth above the low tone. This means that what we ACTUALLY heard during your demonstration was the first harmonic, second harmonic, and the third harmonic. The fundamental would have sounded an octave BELOW what I'm calling the low tone.
"The fundamental and harmonics of a corrugated tube are lower than those of an uncorrugated tube of the same length and diameter" "The difference in speed between the moving end of the tube and the stationary, hand-held end creates a difference in air pressure. A higher pressure is at the fixed end and a lower pressure is at the moving end." en.wikipedia.org/wiki/Whirly_tube
I have kind of a... hard question...? My teachers are clueless, as my interests are beyond what i have in school. Tried to ask, didn't get answer. How light is able to be affected by gravity, without mass? Internet says it's due to curved space-time. But the curve is caused by the gravity itself... no? I came to this question studying gravitational fields, and remembering that black holes can "suck up" light, as well as gravitational lensing... existing. I also tried to do something my teachers tols me was stupid. Ive matched E=mc^2 with E=hf exations to calculate hypothetic "mass" of photons of specific wave frequency. The result was pretty reasonable, as mass was about 10^-5 smaller than the mass of an electron. Help. The question. I'm very confused.
@@lecturesbywalterlewin.they9259 But I did and the only answer I've seen was that it changes its path due to space-time being curved. But thank you for response and time you put in teaching people. You've helped me immensely in understanding classical mechanics! @edit I've foundly founs my answer. I can finally rest in peace! :D
Fun facts: As young boys we had these toys and swinging really hard, we could get up to 9f0 or so. I became quite acquainted with the musical sequences. As a student I studied the perception of overtone singing, where the same sequence came back. (For anyone interested: see The Journal of the Acoustical Society of America 92, 1827 (1992), or www.ncbi.nlm.nih.gov/pubmed/1401528 Mariah Carey's 'All I want for Christmas' contains the theme g-b-d-f#-g-f#-d-b which is the overtone series 4f0-5f0-6f0-7f0-8f0-7f0-6f0-5f0 of the fundamental frequency f0=392 Hz (g).
And until 2004 I travelled daily by electric trains. In the double-deck trains, when sitting near the electric transformer or motor, one could hear a soft humming when the train departed. As the train gained some speed (and more power was needed to keep it accelerating), you could hear the pitch of this humming jump up stepwise. Again, these were tones of a harmonics series. The octave and fifth interval were represented, so if it's something like an arrangement of coils that are switched on to a circuit, I would guess that the setup had a hexagonal symmetry. Does anyone know the details of this? Are extra coils switched on, or is DC just converted into different frequencies to influence power transmission in some other way?
Dear Dr. Lewin, I have a mix up in my terminology, I think you can clear things up. I did the following experiment: I have air flowing through a straight pipe. Pressure ratio between outlet and inlet is lower than the critical pressure ratio, which suggests flow velocity at the outlet is close to the speed of sound. I have recorded the sound of this process and analyzed the frequency spectrum. Suprisingly for me (but maybe not for you), the dominant frequencies are in a integer ratio to one another. So this would imply a standing wave behaviour.. but can it be called that? The air is moving at a great speed through the pipe after all. I search on the web for explanation, of little avail. Literature containing a mathematical approach would be greaty appreciated. Take care, love your videos.
@@lecturesbywalterlewin.they9259 Thank you for the quick answer! It makes a lot of sense that the sound waves are superposed on top of the unidirectional gas flow.
@@lecturesbywalterlewin.they9259 I have followed your recommendation. Also, a good resource on my particular experiment in aeroacoustics is from Prof. Hirschberg of TU Eindhoven (page 62), available here: www.academia.edu/26051611/Introduction_to_aero-acoustics_of_internal_flow
Dr. You said fundamental 1st and second harmonic but in your lectures you said that you hate when books call them fundamental and 1st and you said to your students to name the fundamental the 1st harmonic , what have changed ? :pp
@@lecturesbywalterlewin.they9259 we all change 😋 personally i will always call the 1st harmonic the fundamental (f) so the 2nd H will be 2f 😊 have a nice day and "physics works"
@@joeydemiane2070 What counts is that there should never be any ambiguity. If someone ONLY uses the words "1st harmonic" and nothing else, then you may not know whether it is the fundamental or twice the freq of the fundamental.
Thank you sir.I am from Kolkata,India. After seeing your video we are highly inspired to learn and teach physics in different ways by relating to natural things happen and demonstration.I like your way of teaching.😊
Griffiths: Introduction to electrodynamics. Griffiths: Introduction to Quantum Mechanics Arfken: Mathematical Methods for Physicists Gould: Statistical and Thermal Physics
Dr Lewin. You are the most intelligent human I have ever seen. I am from India and am preparing for GATE 2020. Thats a test of engineerimg graduates. In the moments I feel low, demotivated I watch your videos. They inspire me a lot. Thank You for Everything. Love You Sir.
So... how was your GATE?
2:45
share this with someone esle and dont say anything and dont show the tiltle😂😂 Great video btw👌👌
Nothing like physics to keep your mind well oiled. Thank you Professor Lewin.
Amazing experiment sir i have seen 1,2and 3rd harmonic in mechanical wave experiment with heavy chain 🔗 but listened to it 1st time in my life. Thank sir. 🙏🙏🙏🙏🙏
Absolutely awesome. I know a lot about music theory and how the overtones are generated, but I learned a lot here about how the tube generates it's fundamental frequency when passing air over one end! And it's amazing how just by swirling it faster (passing the air faster?) you get the higher harmonics!
Visualised organ pipes like never before... Thank you hon'ble sir🙏
Sir... For the first time i have seen this.... I will try it when i get a pipe by myself... Thank you soooooo mich sirr..... Love you
U are one of the legend Sir. .......
This is so much better than all theory i was reading and couldn't understand a word. Thank you so much.
You're very welcome!
You're the best teacher in the world! And have the most beautiful shirt, really! I would like to own this shirt. Regards from Brazil.
BR encontrado
Sir u r an inspiration to all, u r an example of how a teacher should be, love from Pakistan.
Wow, I'm from Pakistan too!
Watching the video for my MCAT xD
Sir , India probably is your largest fan base. We heartly welcomes you here. Considering how love from India for professor is tremendous, I believe you should have tried coming to India frequently. Probably if you would have done so , you can count and miss every single visit here.
Sir don’t get disappointed by seeing the number of views....these months are very crucial time for jee aspirants...in India...So ....love physics !!love you sir!!!
PSS X Thats not something that reduces the views..Even I’m a jee aspirant. These problems genuinely help me and i do hope that he doesnt stop making these
Aniket Pai but few parents or....some one stop them from watching these right.
?just to concentrate .........iam damn sure that’s how ever watches these ...they are interested in physics.........and as always love physics!,!
Love you sir from India.... I love physics and you inspire me everytime............... Everywhere.......
To find the fundamental frequency we can use the formula f=V/(2L) since it’s an open/open pipe.
V=the speed of sound which depends on the temperature but I will assume it is 20°C
To find the speed we use the formula:
331+0.6T
331+0.6•20=343m/s
Now we plug this into the original formula:
343/(2•0.76meters)=226Hz approximately.
To find other harmonics we simply multiply the answer by 2 and 3
451Hz
677Hz
Sir u are best physics teacher of this world
Thank u for another problem professor..........nice to see u again....💙💙💙
Dir Lewin,
I've seen almost all of your videos their are the most knowledgeable and fun way to learn, waiting for new ones.
I'll do anything in order to meet you even for 5 minutes.
Looking forward to meeting you.
we can meet in Cambridge MA, USA. I will meet Richard Xu here in Cambridge tomorrow (Sunday) morning.
Professor Lewin, is there any other day we can meet?
2:54 he seems some kind of a Jedi master at this instant when he just introduced the 2nd hormonic...
It's an amazing video .. hillarious! 🤣
He has red rotating lightsaber and hence he looks like inquisitor
All concepts Clear, Thank You So Much Legend ❤
This reminds me. You should do a video on the doppler shift as well.
Sir, I am from India. currently in the final year of my bachelor's degree in Physics.
First, I would mention (as I also have a drop of knowledge from the ocean of music!) that the second note that was generated was not an octave up but was the fifth up note of the first note i.e. the fundamental note.
Coming to the problem, we know that the fundamental freq. (let it be F0) in an Open-Open pipe is given by f0=v/2L where, F0 is the fundamental frequency; v is the velocity of sound in air and L is the length of the pipe used. As you say and I trust you that the length of the pipe is 76cm=0.76m and the velocity is known to us to be 346m/sec. when we substitute these values in the equation of the F0, we get f0=227.63Hz.
And the succeeding harmonics (except 1st Harmonic) will be the integral multiples of F0. i.e. F1=227.63 F2=455.26 and so on. The reason why F0=F1 is because that the pipe is open at both the ends.
Witnessing legend getting old 🥺
Thankyou for last 7 years sir
How beautiful is Physics.....💜💜
What you were saying was the fundamental wasn’t the fundamental though, it was the first harmonic. Because the next harmonic up was a fifth higher, not an octave
I accept your judgement - students at MIT have also mentioned this to me. Please send me the frequencies of the 3 resonances that I excited. When I give the solutions, I will give you credit.
I went down the comments to see if someone had written about that already.
The first harmonic has twice the frequency of the fundamental, that is, a full octave. The "first" harmonic in the video sounds a fifth above the "fundamental", therefore we can conclude the "fundamental" was actually the first harmonic and we really never heard the fundamental. It still amazes me that our brain is capable of doing the equivalent of Fourier's transform and recognize the different frequencies.
Players of brass instruments are very aware of this, as it is the principle of the instrument and, especially for horn players, we have warm up exercises going through the harmonics in all tubes combinations.
Still, this is a very interesting exercise thank you, Walter :) now I'll watch your lectures on the topic ;)
Lectures by Walter Lewin. They will make you ♥ Physics. How do I send the solution?
@@georgH plse send me the frequencies of the 3 resonance freq that I produced
Thank you very much - I will mention you in my solutions.
Wow Sir Lovely 😍
Simple model for open open tube yield a spectrum of frequencies for each natural number n given by:
f=n*v/(2L) where v is speed of sound and L is length of tube
Using v=340m/s and L=0.76m, we get about
f=n*224 hz
Thus the fundamental is 224 hz, the first harmonic is 448 hz, the second harmonic is 672 hz, the third harmonic is 896 hz
In the experiment you performed, the notes sounded close to Aflat4, Eflat5, and Aflat5, which has frequencies of about 415.3 hz, 622.3 hz, 830.6 hz (standard equal temperament A4=440 hz tuning)
These are reasonably close to the calculated values for the first, second, and third harmonic respectively, and the pattern lines up with those harmonics (a perfect fifth then a perfect fourth). Thus the actual fundamental if you could excite it would probably be close to Aflat3=207.7
The error between 207.7 and 224 is likely due to variation in speed of sound and end effects not taken into account in the simple model.
"The fundamental and harmonics of a corrugated tube are lower than those of an uncorrugated tube of the same length and diameter" "The difference in speed between the moving end of the tube and the stationary, hand-held end creates a difference in air pressure. A higher pressure is at the fixed end and a lower pressure is at the moving end." en.wikipedia.org/wiki/Whirly_tube
Lectures by Walter Lewin. They will make you ♥ Physics. Interesting, thanks
You are my hero sir love you...........
very nice demonstration
It's amazing 😍❤️❤️❤️😍
Amazing video professor!
Sorry to be a party pooper here. What I heard was an A flat, the low tone; E flat, the middle tone; and A flat the Hi-Tone. What I'm calling the low tone sounded an octave below the high tone and the middle tone was a perfect fifth above the low tone. This means that what we ACTUALLY heard during your demonstration was the first harmonic, second harmonic, and the third harmonic. The fundamental would have sounded an octave BELOW what I'm calling the low tone.
you are right!
"The fundamental and harmonics of a corrugated tube are lower than those of an uncorrugated tube of the same length and diameter" "The difference in speed between the moving end of the tube and the stationary, hand-held end creates a difference in air pressure. A higher pressure is at the fixed end and a lower pressure is at the moving end." en.wikipedia.org/wiki/Whirly_tube
I have kind of a... hard question...? My teachers are clueless, as my interests are beyond what i have in school. Tried to ask, didn't get answer.
How light is able to be affected by gravity, without mass?
Internet says it's due to curved space-time. But the curve is caused by the gravity itself... no?
I came to this question studying gravitational fields, and remembering that black holes can "suck up" light, as well as gravitational lensing... existing.
I also tried to do something my teachers tols me was stupid.
Ive matched E=mc^2 with E=hf exations to calculate hypothetic "mass" of photons of specific wave frequency.
The result was pretty reasonable, as mass was about 10^-5 smaller than the mass of an electron.
Help. The question. I'm very confused.
use google, it's all there!
@@lecturesbywalterlewin.they9259 But I did and the only answer I've seen was that it changes its path due to space-time being curved. But thank you for response and time you put in teaching people. You've helped me immensely in understanding classical mechanics!
@edit I've foundly founs my answer. I can finally rest in peace! :D
Fun facts:
As young boys we had these toys and swinging really hard, we could get up to 9f0 or so. I became quite acquainted with the musical sequences.
As a student I studied the perception of overtone singing, where the same sequence came back. (For anyone interested: see The Journal of the Acoustical Society of America 92, 1827 (1992), or www.ncbi.nlm.nih.gov/pubmed/1401528
Mariah Carey's 'All I want for Christmas' contains the theme g-b-d-f#-g-f#-d-b which is the overtone series 4f0-5f0-6f0-7f0-8f0-7f0-6f0-5f0 of the fundamental frequency f0=392 Hz (g).
nice!
And until 2004 I travelled daily by electric trains. In the double-deck trains, when sitting near the electric transformer or motor, one could hear a soft humming when the train departed. As the train gained some speed (and more power was needed to keep it accelerating), you could hear the pitch of this humming jump up stepwise. Again, these were tones of a harmonics series. The octave and fifth interval were represented, so if it's something like an arrangement of coils that are switched on to a circuit, I would guess that the setup had a hexagonal symmetry.
Does anyone know the details of this? Are extra coils switched on, or is DC just converted into different frequencies to influence power transmission in some other way?
That's so intresting!!!
You are great
Amazing ❤
Ah,I just saw your lecture(a few days back) on this
You are great ♥️
Amazing
Woow, amazing. I did'nt expected that. Prof Lewin do you have donation site or something like that? I appreciate what you do.
You are amazing sir
LEGEND.....
Dear Dr. Lewin, I have a mix up in my terminology, I think you can clear things up.
I did the following experiment: I have air flowing through a straight pipe. Pressure ratio between outlet and inlet is lower than the critical pressure ratio, which suggests flow velocity at the outlet is close to the speed of sound. I have recorded the sound of this process and analyzed the frequency spectrum. Suprisingly for me (but maybe not for you), the dominant frequencies are in a integer ratio to one another. So this would imply a standing wave behaviour.. but can it be called that? The air is moving at a great speed through the pipe after all.
I search on the web for explanation, of little avail. Literature containing a mathematical approach would be greaty appreciated.
Take care, love your videos.
ofcoz these are standing waves - watch my 8.03 lectures where I cover this in detail.
@@lecturesbywalterlewin.they9259 Thank you for the quick answer! It makes a lot of sense that the sound waves are superposed on top of the unidirectional gas
flow.
@@ThomasHaberkorn there is no unidirectional gas flow. There are 2 identical flows in opposite directions. watch my 8.03 lectures in which i coe this.
@@lecturesbywalterlewin.they9259 I have followed your recommendation. Also, a good resource on my particular experiment in aeroacoustics is from Prof. Hirschberg of TU Eindhoven (page 62), available here: www.academia.edu/26051611/Introduction_to_aero-acoustics_of_internal_flow
Here we go boys!
I think that the fundamental frequency is the same thing with the "1st harmonic"...
We have a lot of ur fans here in india
Professor Lewin please make a video about Richard Feynman.
And his preoccupation with Tuva, where he and Ralph Leighton finally managed to get, by attending a conference for overtone singing!
that is an amazing shirt!
i enjoyed second harmonic.
Sir u r great
thanks 😍👏👏👏
Nice
thanks a lot dear
Where do we send the solution to the problem ??
Thank you sir
Thanks alot sir
How come he has such a large fan base in India?
Wow .....1.
Nice man
❤️❤️
Sir, I have a doubt , will a current loop placed in a magnetic field always experience a zero force?
watch my 8.02 lectures where I cover this - including torques.
Nope. Not always. Although when the field is perpendicular to a the plane of the loop and is uniform with space it experiences zero force.
sir should i post my answers here ?
Dr. You said fundamental 1st and second harmonic but in your lectures you said that you hate when books call them fundamental and 1st and you said to your students to name the fundamental the 1st harmonic , what have changed ? :pp
Maybe in 1999 (20 yr ago) I felt that way. I now like to word "fundamental". I believe I address this issue in my solutions (I don't remember).
@@lecturesbywalterlewin.they9259 we all change 😋 personally i will always call the 1st harmonic the fundamental (f) so the 2nd H will be 2f 😊 have a nice day and "physics works"
@@joeydemiane2070 What counts is that there should never be any ambiguity. If someone ONLY uses the words "1st harmonic" and nothing else, then you may not know whether it is the fundamental or twice the freq of the fundamental.
@@lecturesbywalterlewin.they9259 100% 😉👍
😍😍😍😍😘
Thank you sir.I am from Kolkata,India. After seeing your video we are highly inspired to learn and teach physics in different ways by relating to natural things happen and demonstration.I like your way of teaching.😊
Sir now I have given my exams I want to prepare for SAT subjects in physics
What should I study?
Where should I start? I don't have any idea
use google and talk to teachers who prepare students for SAT and talk to students who took SAT
2:36 - 2:45
Professor, if our universe and distant galaxies are expanding at the speed of light, could it be considered a perpetual motion machine?
google perpetual motion machine - then decide
God bless you Mr. Lewin 😊👍👍👍
Sir tomorrow is my exam need your blessings
You have my blessings!!!
Suggest me the best book of Physics
After highschool
Griffiths: Introduction to electrodynamics.
Griffiths: Introduction to Quantum Mechanics
Arfken: Mathematical Methods for Physicists
Gould: Statistical and Thermal Physics
I NEED THE SHIRT YOUR WEARING :D
I am indian
You are great