F-J's Physics - Barton's Pendulums and Resonance - Video 35
ฝัง
- เผยแพร่เมื่อ 1 ต.ค. 2024
- A fabulous demonstration of resonance and on such simply made equipment. And time for more teddy bears on loudspeakers too.
Please consider supporting my work by buying me a coffee at
www.buymeacoff...
Very many thanks, F-J
![[Live] ศึกมหึมันส์มวยไทยสังเวียนเดือด เวทีมวยชั่วคราวสวนสยาม | จันทร์ 30 กันยายน 2567](http://i.ytimg.com/vi/pM1k6f7JXUc/mqdefault.jpg)
![[DEMONSTRATION] - Resonance: Torsional Oscillator and Barton’s Pendulum](/img/n.gif)
Hope you enjoyed the video. If you did please consider supporting my work by buying me a coffee at www.buymeacoffee.com/francisjonesa Very many thanks, F-J
can we all take a moment to appreciate this man's music taste lol that bass tho
I was reading and rereading the chapter regarding the same experiment and I couldn't understand it but gosh! You explained it in one go! Thank you so much!!!
Pleasure! So pleased it helped. Good luck with your studies and, as ever, enjoy your physics!
This is masterpiece.. Thanks a lot for clear and awesome explanation
Many thanks and really pleased that you enjoyed it and found it useful. I had fun making it. It is an interesting experiment.
@@AnthonyFrancisJones you sir you genius
Please don't stop making it.. Do with some qm
Thanks - I will try to keep them coming - do suggest topics and if it fits with the sort of thing I do I can give it a go.
@@AnthonyFrancisJones try some magnetism
Think I have done a few now!
Good explanation in detailed sir
Thank you and great that you found it helpful. Thanks for taking the time to comment and wonderful to hear all the way from Sri Lanka!
Wow what a wonderful experiment sir..!!!
you really explained the Resonance Mechanism in a wonderful way.
Yes, it is a great experiment. Why don't you try and build one - really simple. Thanks for your very kind comment and so pleased it helped you with your physics.
Fantastic explanation of why the cone with the same length oscillates at the same frequency. Resonance. But why? Because take the maximun energy from the weigth pendulum, because its natural frequency of oscilation is the same.
Other interesting point is the phase, since they are 180° out of oscilation phase, interesting but not so clear.
Thanks for your kind comment. Careful with the phase bit - if they were 180° out of phase the displacements would add to zero! So they are 90° out of phase. Think of pushing a child on a swing. When they are at the top of the arc - stationary, you move most to push them. It is a similar situation here. I have not gone into the maths or the graphs of displacement, velocity and acceleration/time but it is worth looking at these too. Hope that helps and thanks so much for watching!
I'm Persian student and I have to say that awesome .... Maybe my English language isn't very good but you explained so good .... Thanks for explaining it
Mohsen - your English is excellent and way better than my Farsi! So pleased that you found it helpful and thank you for taking the time to comment. Enjoy your physics!
Oh am persian too
Thank you for this useful video on Barton Pendulums, especially when you related it, in the end, to some applications.
Pleasure and thank you for taking the time to comment. It's a lovely bit of physics and has so many applications. I felt that it might have been a bit of a 'forgotten experiment'. As ever, enjoy your physics!
Thanks for helping me understand this!
Pleasure - Glad it helped.
After watching 10 videos now I get it
Thanks Suzan - so pleased that it helped. Lovely experiment this one and I did not get to teach it this year due to schools being closed.
I have had these doubts forever and no one seems to comprehend them:
Why are the other pendulums (non-resonant ones) also vibrating at the same frequency as the driver and perfectly in phase(I'm assuming being in phase means to touch extremes simultaneously) too? Are these what forced vibrations are.. as in the case of forced vibrations, the body under the effect of an external periodic force acquires the external force's frequency at a small amplitude even if its own natural frequency is different?
Is it that all the pendulums and the connecting 'washing line' are vibrating at the same frequency, just that only the driver and second to longest ones are resonating because they have the same natural frequency and so have the largest amplitudes?
Ok, so I will try my best taking your questions in order. The non-resonant pendulums are not at the same frequency (they are non-resonant). They are almost there but not quite - too high or too low compared with the swinging mass and the single resonant one. Being in phase means, in simple terms, swinging together side by side without every changing that line up as it were. They all are not doing this as they are all swinging at different frequencies to each other and the swinging (driver) mass. So if the force acting on on of the pendulums is such that it 'pushes' against the direction of travel that pendulums amplitude (highest swing point) will get less and less. Finally you say, "only the driver and second to longest ones are resonating because they have the same natural frequency and so have the largest amplitudes" is correct. Do hope that helps and thanks for a great set of questions. Not an easy bit of physics!
@@AnthonyFrancisJones Thanks for your quick response! I have learnt that when an external periodic force acts upon a vibrating body, the vibrating body acquires the frequency of the external periodic force gradually irrespective of whether its own natural frequency is equal to the frequency of the external force. (forced vibration)
if its natural frequency is equal to the frequency of external force, the body resonates.
if its natural frequency is unequal to the frequency of external force, the body oscillated at a small amplitude.
This is what first led me to the assumption that the non-resonating pendulums are forced into vibration at the frequency of the driver but vibrate only with a small amplitude because their natural frequencies are not equal to the one of the driver but as you said, their frequencies are almost there but not quite...
@@thecomplexity Yes, that's right. All the pendulums feel a periodic FORCE at the frequency of the driving mass but do not move AT the same frequency unless they are resonant and even then the oscillation is 90 degrees out of phase. Now there is a situation where two 'distant' (very very lightly coupled) systems such as clocks on a wall or metronomes will at first be ticking out of phase but will very slowly move in phase but they of course have the SAME natural frequency. Perhaps this is what you were thinking of. Anyway hope some of this helps and good on you for asking!
Is the pendulum with weight oscillating at its natural frequency? And if yes then how? Coz the vibration is damped vibration and in damped vibration the frequency is less than the natural frequency. And if it is not vibrating at its natural frequency then how is resonance occuring?
Good question - yes it is oscillating at its natural frequency as it is a 'free' not 'driven' oscillation so by definition it is at its natural frequency. Yes, it is slightly damped but one can consider that that is only an energy (amplitude) loss. The pendulum provides the periodic force to the other masses - paper cones. They then demonstrate resonance where the periodic frequency they are driven at is similar to their own natural (or resonant) frequency. Not an easy one to grasp! Hope that helps!
WONDERFUL! Physics bless you sir, that's an amazing lecture.
My pleasure and I am so pleased that it has helped with your studies. Keep up the great work! It will be worth it!
hello. what happens if at stationary, we swing the paper cup with same length rope, will that resonate and move the heavy weight to similar speed ? does the kinetic energy transfer regardless of body mass ?
Good question - yes it would cause the heavy mass to begin to oscillate as expected but it would not have as much initial energy as it is lighter so the movement of the heavy mass would not be as large. But, as you guessed, they will have similar natural frequencies so energy will move between them. Perhaps you can see now why we use a heavy mass to drive the system instead of having a second paper cone of the same length. Great question and thanks for asking!
your demonstration is very interesting also ur explanation is also clear
Thanks for taking the time to comment and glad you found it useful and interesting.
Could you please explain why the phase difference
Thanks for the question. Each length has a different natural frequency so swings at a different rate/frequency. Short is higher in frequency than longer - a bit like strings on a piano. If they swing at different frequencies there will be a phase difference between them. i.e they will not always be in line with each other. But the weight and one of the pendulums (of the correct length) will always be swinging together at the same frequency but with a difference in 'position' that remains the same between them all of the time. So they are not in phase either but have a constant phase relationship. Hope that helps.
very good explanation. I understand resonant frequency a lot better now. Thanks for the help!
Absolute pleasure - glad you found it useful!
Thank You Sir...
I understood it well....
I am from India...
Thanks Reshma. This seems to be an experiment that is seen as very important to understand in India. I am not sure so many people in the UK see it but I am so pleased it helped and good to hear that physics remains strong in India! Good luck with your studies.
Our physics teacher showed this video in the class
Great! Hope the class found it useful. Your teacher should build one for you too!
Sir, when did you make this experiment? I need the time information for my paper. Thank you
My pleasure: Filmed on 20/04/2018 and published on 26/07/2018 in England, UK Hope that helps.
Thank you so much. Hopefully I can learn much from you.
My pleasure and good luck with the project.
like if inspired by jindal sir
Glad you liked the video and hope you found it really useful. Good luck with your studies!
Glad you enjoyed the film and I hope it helped you understand this interesting bit of physics!
You took only 7 mins, to teach what my tutor taught taking half an hour. Keep the good work going! All the best! From Sri Lanka
That's very kind of you and great to hear that you are watching in Sri Lanka - As I always say, 'Enjoy your physics'!
@@AnthonyFrancisJones I've a doubt, Instead of small cones, why don't we consider heavier weights more appropriate ? Even when measuring gravity using a pendulum, we use bobs around 100g, why is that ?
@@onelaperera7936 Good question. So you will notice the weight that gets the cones oscillating is quite a large mass compared with the cones so it stores a lot of energy. The cones are light so the slightest amount of energy transferred to them makes them move - they only need a small amount of gravitational potential energy to swing high up - heavy ones would need much more to get to the same height. Now, measuring g you want to eliminate the effects of drag/air resistance so make the mass of high density and small size so a brass bob or similar is excellent for this. Hope that helps explain it!
@@AnthonyFrancisJones yes!understood, THANKYOU SIR
@@onelaperera7936 Pleasure!
Thank you so much for the great explanation. It helped me understand resonance a lot better
Ember - so pleased it helped. Not an easy topic but a nice little experiment. Do continue to enjoy your physics.
@@AnthonyFrancisJones I sure will :)
Hello! I was wondering, will the shortest string have the smallest amplitude (since it is the furthest away from the driver string in terms of length), or will the amplitude be equal for all of the strings (other than the resonant one) once everything has settled?
Good question. On this scale the distance from the driver makes little difference. You need to have a look at 'resonance curves' which show that as the length gets further from the resonant length the amplitude (once 'settled down') is lower. The order of the strings here does not matter either, it is just they are typically put in reducing length order so you can almost see the shape of an amplitude vs length curve! Hope that helps and thanks for watching.
@@AnthonyFrancisJones Thank you for your reply! To clarify, by " as the length gets further from the resonant length," do you mean only a length greater than the resonant can have the lowest amplitude, or just the one with the biggest difference in length (compared to the resonant length) ?
@@randomhumand4757 As the length gets smaller or larger than the resonant length (length of the driver) the amplitude reduces. It is not a linear relationship but have a look at resonance curves and you will see. It applies in lots of situations from swings to tuning circuits in radios. So as you say the lowest amplitude will typically be the length with the biggest difference in length, but before I get corrected it is not quite symmetrical around the resonant length with amplitudes dropping off more rapidly with higher frequencies. Google resonance curve and it will help explain things even better!
Respected Sir 🙏🏻. Thankyou very much .
Can you please tell me that whether these pendulums vibrate with the same frequency , which is equal to the frequency of the external periodic force ( as written in my book ) or do they vibrate with different frequencies ( which depends on their lengths)?
Good question. They vibrate at a range of frequencies (dependent on their lengths) all close to that of the periodic force. The one that vibrates the most (highest amplitude) vibrates at the frequency of the periodic force (or multiples of it). Have a look at 'resonance curves" that might help you understand better what is happening. Thanks for the question and I hope that helps.
@@AnthonyFrancisJones Thankyou very much Sir 🙏🏻.
I couldn't ask for a clearer video😊😇 thank you!
Thanks for you kind comment - so pleased you found it useful.
Thank you very much sir.
I could understand the theory by watching this practical.The only question was solved.
Physics is not solving problems,it's a practical subject.
Great - so pleased it helped you understand what is not an easy practical demonstration to get the hang of. Hope your studies continue to go well!
Thnx sir
Pleasure - glad you found it useful.
You're tremendously well-spoken and not simply for your charming accent, like so many of your countryfolk.
Thank you for sharing a bit of your knowledge and a bit of your skill-set. I hope you do well in life, good sir!
Thank you - that's really kind. I never think of myself has having an accent but I know what you mean! Pleased that the video helped. It is a great experiment and good luck with all your physics studies and thanks for watching!
Thank you Sir .....this video really help me for solving my queries....👍
Thank you. I am really pleased to hear this. Again, a simple experiment but tricky physics behind it! Good luck with your studies!
Thanks for helping 😊 I couldn't understand it from the book
Excellent - so glad it helped.
good video 👍
Thanks. Glad you liked it and found it helpful. Good luck with your studies.
Carried me through my Alevel pag, thanks
Excellent Henry! So pleased it helped. I guess you are ending your A Level this year but if you need it there are full lessons on Gravitational Fields, Electric Fields, and Waves in my Corona Buster playlist. Thanks for taking the time to comment and good luck!
@@AnthonyFrancisJones Nope! I'm in year 12, it just our teachers are desperately speeding through everything so we can then go back onto the stuff that need to be re-learned or just properly understood. I may become a regular visitor here for the next year haha, thanks
@@henrygavin6034 Great - glad it is helpful. I do hope to do more A Level stuff - I have done a series on Waves for AS level in the Corona Buster playlist - just me teaching but my A Level pupils found it useful during lockdown and they also used all the lessons on Gravitational Fields too. Thanks for taking the time to comment and best of luck with your physics!
One question from this concept came in KVPY SB 2007 (Q25)
Great - I think it is a bit of a forgotten experiment but of course the physics behind it is frequently asked about in exams usually in a 'real life' situation. I had a hunt for the question but I could not find it. I would be interested to see it. Those exam papers are excellent.
Thank u
Pleasure - glad you liked it!
teddy bear is so me sitting on the washing machine
If it would be absorbing vibration. is would be eliminating it. you are using a wrong word. It is actually opposing the vibration.
Thanks - not quite sure of your drift. You cannot absorb vibrations - you can 'transfer the energy from the vibration's kinetic energy' if that is what you mean. In terms of opposition, there is a pi/2 phase shift so the oscillations are not really in opposition (I suppose that would be pi radians out of phase). It is an interesting demonstration and not that easy to explain fully. Coupling between oscillating systems is tricky at the best of times! Regardless, thanks for watching and taking the time to comment.
Thnx a lot
Pleasure. Glad you enjoyed it and hope it was useful. It is a lovely demonstration.
Thank you so much for the deep explanation 🙏
My pleasure. Glad you found it useful and it helped with your understanding of physics. Plenty more on my channel should you need more help!
Why did he use heavy mass for first pendulum?
Good question - all the heavy mass has to do is provide a vibration at one specific frequency. This will cause the others to vibrate and the one that is the same frequency will vibrate best (highest amplitude) as at resonance it absorbs energy from the heavy one best. Now the store of energy in the heavy one will depend on its mass and it is losing energy all of the time to keep the system going so the more mass (and therefore energy) it has the better. It would work with a lighter one but would not keep going for so long. Hope that explains it and thanks for your question.
@@AnthonyFrancisJones I learned this in university, I think heavy mass pendulum doesn't provide one specific frequency. It gives one specific Amplitude. And a nother question, according to forced frequency (heavy mass pendulum) , all the lighter pendulums oscillate same frequency (heavy mass pendulum frequency) ?
@@realphy6656 No, in both cases! The heavy mass is at one frequency but it can still cause others to oscillate just either side of resonance - yes, you could argue that it does provide amplitude as if it did not nothing else would move but not a specific amplitude - any reasonable amplitude will do as frequency is independent of amplitude! All the lighter pendulums do not oscillate at the same frequency - that is the whole point of this apparatus - they oscillate at frequencies near to the heavy mass but not at its frequency - that's why you see the phase shift between them all. Hope this helps and I have done a reasonable job of explaining it. I guess the real problem is I try to explain things without just using maths as a way of doing it!
@@AnthonyFrancisJones Thank you very much. I got this.
@@realphy6656 Great - it is not easy but once you get it it all makes sense!
Well explained !!
Thanks! Glad you found it useful and good luck with your studies.
Thank u very much sir
Pleasure - glad you found it useful!
thank you so much for this video sir
Pleasure - glad you enjoyed it and it helped you - it's a nice demonstration that everyone should see.
@@AnthonyFrancisJones yes! also I wanted to say that today I had physics exam and there was a question exactly about this experiment, and I could easily answer it because of this video! I'm so thankful!
@@tinataheri4559 That's brilliant! So pleased! It is easy to build so all schools should have one to demonstrate. So much physics in it I thought I had overdone it in the video but it's too good not talk about! As ever, enjoy your physics and hope the videos help. I must publish all my ones on OCR topics such as Gravitational Fields and Waves as well as how to handle data.
Thank you!
Pleasure - hope you found it useful.
Thank you
Thanks Yasir and good luck with encouraging others to learn more about the wonderful subject that is physics!
@@AnthonyFrancisJones Thank you dear Francis! :)
Thank you for the great and clear explanation
Great - thanks for commenting and glad you found it useful.
this helped a lot! thank you
Min Linting - thanks for letting me know - it is a lovely experiment and every physics student should see it. Hope you enjoy some of my other physics videos too. Good luck with your studies.
nice explanation .thank you sir.
My pleasure Dulmi - so pleased you found it useful. It is a lovely experiment. As ever enjoy your physics!
awesome one
Thanks, hope you found it useful.
@@AnthonyFrancisJones my teacher suggested me your video...!!!
You must have a great teacher! Thank them on my behalf and hope your studies are going well!
gj
Thank you sir 😊
Pleasure - glad you enjoyed it and found it useful.
Hi sir. Regarding pendulum tuned mass dampers, I've read that for them to be optimal, they have to resonate out of phase with a system (e.g. a building). However, as seen in this demonstration, most energy is absorbed by the pendulum with the same frequency as the driver pendulum, but it only has a phase difference of pi/2 rather than pi. How is it possible for the tuned mass damper to be optimal when it resonates out of phase rather than with a phase difference of pi/2? I'm a little confused and hope you can help me. Thank you for this brilliant demonstration regardless!
Excellent question Andra. So if I understand it correctly in terms of the situation you are explaining: To drive a system and make it absorb energy best you want to be oscillating with a pi/2 phase shift - you are right about that. However, if you want to dampen (reduce the oscillation) then you have to have a mass move out of phase with the mass you want to damp in many cases - called Tuned Mass Dampers or TMDs. Taipei 101 is a great example of the use of a TMD. Not really a great explanation (and no maths) but I hope you get the idea that there are engineering solutions that use pi phase shifts. Hope that helps a bit and do enjoy your physics.
@@AnthonyFrancisJones Hi sir. Just a quick follow up. Doesn't damping imply the system dissipating energy? So if that's the case, why isn't the reduction of the oscillation at a maximum (critical damping I believe?) if the tuned mass damper is at a pi/2 phase shift, rather than a pi phase shift? If damping is due to the system dissipating energy, isn't it better for the tuned mass damper to absorb the most energy from the system? Thank you very much for your reply!
Sorry to ask so many questions. It's just that I am currently doing my physics project on (pendulum) tuned mass dampers, and would like to solidify my understanding. Thank you so much.
@@AndraHueiHsiaLye - pleasure - not sure I really helped but hope your project goes well! Let us know how you get on.
@@AndraHueiHsiaLye OK, I think the difference is between damping - which in many ways is what this video shows - the heavy mass has energy taken from it not by friction (only) but by the tuned cone wanting to swing at the same frequency but pi/2 out of phase. The pi phase damper moves (applies a force) in the opposite direction to an oscillating system to stop it moving rather than to reduce energy. So one system 'steals' energy, the other system is designed to stop it starting to oscillate in the first place. So two different situations. In the second system the mass that is stopping it oscillating is not just freely moving but is driven by hydraulic rams. In the first system there is no 'motor system' making it work. I have see these pi shift systems on the sides of large ships to reduce the oscillations in the waves. They do not take energy out of the system, they just stop the oscillation happening and building up in the first place. Hope that makes sense and thank you for your excellent questions. You learn and I have to think too - all good science!
WOW SIR...THANK YOU FOR THIS .
Thanks, Glad you liked it. It is a great experiment!
Vivid explanation. Thanks a lot
Thanks, so pleased it was helpful - I think it is a bit of a forgotten experiment but I am glad that people still know about it and take an interest.
Thank you
Adrian - glad you liked it - seems to be a popular topic this one.
very very very very very helpful 😊😊😊😊😊
Thanks - so pleased you found it helpful. Thanks for taking the time to comment.
Great video!
Thanks - glad you like it - another one that was not that easy to film.
You cover very insteresting contraptions, I first found you from the balancing bird, keep up the great videos!
Thanks - the balancing bird was my first and strangely one of the most popular. I plan to do one a week for a year and then see what happens after that - 52 is quite a lot but it is fun and I am so pleased people enjoy them. If there is one you would like me to do let me know and I will give it a go if I can.
DUDE..THIS IS GENIUSS
Thanks Ramya - glad you enjoyed it and found it useful. Do have a look at some of my other videos if you like and as ever enjoy your physics!