Physics Fluency
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Lagrangian Mechanics III: Solving the cylindrical pendulum analytically #PaCE1 #SoME2
In this video, we solve a system of differential equations analytically through the means of linearization, and proceed to discuss the implications of the solution.
For the best viewing experience, make sure to watch in full-screen and 4K (2160p) resolution.
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This is an entry for a contest of Theories of Everything with Curt Jaimungal: ua-cam.com/users/TheoriesOfEverything (specific video for the contest is ua-cam.com/video/V93GQaDtv8w/v-deo.html)
This video is also my submission to the SoME2 event.
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Music in the background from www.fesliyanstudios.com
Blackboard image by Gerd 'geralt' Altmann: pixabay.com/sv/users/geralt-9301/
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#Physics #SoME2 #PaCE1 #Mechanics #Lagrangian #Pendulum
00:00 Intro
01:08 Linearization
03:36 Ansatz
05:17 Eigenfrequencies
09:55 Eigenvectors
11:27 General solution
12:16 Initial conditions
14:14 Recap
15:25 Showcase/Interpretation
19:30 Limiting case
20:50 Outro
Переглядів: 5 228

Відео

Lagrangian Mechanics II: Degrees of freedom, generalized coordinates and a cylinder
Переглядів 12 тис.2 роки тому
#Physics #Lagrangian #Mechanics Sorry about the wait! I hope the audio is bearable. The voiceover is by far the hardest part to get right and I'm still experimenting with how to make it better. I'm also hoping to be able to get a new mic soon. In this video, we introduce the ideas of degrees of freedom and generalized coordinates, before deriving equations of motion for a cylindrical pendulum. ...
Lagrangian Mechanics I: Introducing the fundamentals
Переглядів 68 тис.2 роки тому
In this video, we discover the classical Lagrangian, the principle of stationary action and the Euler-Lagrange equation. For the best viewing experience, make sure to watch in full-screen and with 4K (2160p) resolution. Music in the background from www.FesliyanStudios.com Blackboard image by Gerd 'geralt' Altmann at pixabay.com/sv/users/geralt-9301/ #Physics #Lagrangian #Mechanics

КОМЕНТАРІ

  • @EllisWhitehead
    @EllisWhitehead 7 днів тому

    I wish I could give this more than just one thumbs up! Wonderful explanation.

  • @yuanzhiluo
    @yuanzhiluo 13 днів тому

    The root question is still not explained. The state of the ball can be solely expressed based on U, or solely on T, or solely on V, or solely on (T-V), or solely on another variable like time t. The question is why choosing (T-V), what is the physical meaning of (T-V) if Lagrangian is not invented?

  • @zweisteinya
    @zweisteinya 19 днів тому

    What is q-dot down below in standard notation, do you mean dq^2 ?

  • @jiripingpong6800
    @jiripingpong6800 22 дні тому

    The best explanation of this topic I have seen so far, both by the content as well as by the understandability and visual appeal.

  • @Nyxie405
    @Nyxie405 22 дні тому

    THE BEST VIDEO ABOUT LAGRANGIAN MECHANICS IM ACTUALLY CRYING Edit: Can you make a separate video about Hamiltonian mechanics?

  • @wilurbean
    @wilurbean 26 днів тому

    This is the best explanation

  • @hamidhussain5555
    @hamidhussain5555 Місяць тому

    Could you remove the music because it is so noisy and makes distraction

  • @abdurrahmantpkm1619
    @abdurrahmantpkm1619 Місяць тому

    I am lost in T and V hat, what does hat mean?

    • @ExistenceUniversity
      @ExistenceUniversity 7 днів тому

      The hats mean "unit vector." A V hat means a motion of 1 unit in the direction of V as seen on the graph at 6:19. Likewise, the T hat is a motion of 1 unit in the T direction.

  • @papaohaokip8109
    @papaohaokip8109 Місяць тому

    Please continue your video it's is gem ... So elegantly presented..

  • @papaohaokip8109
    @papaohaokip8109 Місяць тому

    Amazing video...👍👍👍

  • @MathsSciencePhilosophy
    @MathsSciencePhilosophy Місяць тому

    UA-cam recommended it to me after 2 years. I always search for this kind of videos but UA-cam never recognised what I like

  • @BrianDLee
    @BrianDLee Місяць тому

    I was able to derive the first equation of motion at 12:06, however, I don't understand how you derived the second equation of motion. Could you explain this?

    • @BrianDLee
      @BrianDLee Місяць тому

      Nevermind. I realized what you did. You did the euler-lagrange equation again but instead of differentiating with respect to theta1 you differentiated with respect to theta2.

  • @mrslave41
    @mrslave41 2 місяці тому

    wow

  • @carltonbrooks1729
    @carltonbrooks1729 2 місяці тому

    This has given me hope in understanding why T-V. Can this also be deduced by adding the constraint g(x,dx/dt)=T+V -Etotal to represent the conservation of energy?

  • @walterlampert1753
    @walterlampert1753 2 місяці тому

    Great stuff here! Thank you.

  • @jason.arthur.taylor
    @jason.arthur.taylor 2 місяці тому

    I'm sorry, but at 16:48 you incorrectly imply that η(t)=c*y(t). (This is based on your curves.) Because you don't parameterize η(t) into a general function of t, the video is rather incomplete.

  • @ian-haggerty
    @ian-haggerty 2 місяці тому

    So... let me get this straight, You're arguing the principle of least action is equivalent to saying the time average of the lagrangian over any time interval is uniquely determined since the trajectory in energy space is also uniquely determined as a result of deterministic classical mechanics. Therefore, the path that the particle takes must be such that dL = 0, i.e. a local extremum of L, as if this were not the case, a slight variation in path would produce a variation in the lagrangian, thereby producing a path infinitesimally different to the original, but with a different time average of the lagrangian? Thanks 4 the video! Awesome stuff :) Critique welcome of above phrasing!!! It was conceived very quickly.

  • @TheDavidlloydjones
    @TheDavidlloydjones 2 місяці тому

    The unpleasant noise, the supposed "music," played over the voice here is very unpleasant. Looking on the good side, it has shown you who you have in your organization who is so stupid they need to be fired. First, fire the moron. Then re-make the video, OK?

  • @ventyh4244
    @ventyh4244 3 місяці тому

    Amazing video, man! 👏

  • @ChaineYTXF
    @ChaineYTXF 4 місяці тому

    This series is great!! Did you stop making videos?

  • @plutus6316
    @plutus6316 4 місяці тому

    Amazing video! Thank you very much

  • @Jorge_Avila_Balmaceda
    @Jorge_Avila_Balmaceda 4 місяці тому

    these series on lagrangian mechanics are seriously the best videos on lagrangian mechanics I have ever seen! Funnily enough I live about 800 meters away from where Lagrange used to live here in Turin

  • @walterserna3707
    @walterserna3707 4 місяці тому

    Thank you so much for this work. ¿There is a bibliographic reference or an achademic resource that we can use to cite this proposal to understand Lagrangian? or ¿How can we cite your work?

  • @thusithawickramanayaka4493
    @thusithawickramanayaka4493 5 місяців тому

    Behavior of alpha, beta and gamma within a medium......

  • @NA-ud6qm
    @NA-ud6qm 6 місяців тому

    Him: "And that is how we found the Kinetic Energy by making many restrictions~" Me: "... That is one big equation for a super simple problem." Also, Amazing series btw. Can I ask how you create these beautiful animations? Thank you again!

  • @RabijitMahanta
    @RabijitMahanta 6 місяців тому

    Man you are great . your intuition is concrete. Thank you for sharing it

  • @richardhowitt5291
    @richardhowitt5291 7 місяців тому

    Why did we stop for tea?

  • @allenlu2007
    @allenlu2007 7 місяців тому

    The best Lagrangian video series I have seen.

  • @Iovemath
    @Iovemath 7 місяців тому

    But what is the delta δL means? 12:28

    • @minimo3631
      @minimo3631 5 місяців тому

      Wondering this as well, does it mean that the L function will always remain on the "L-axis"? There's two energy and one time direction in which the curve could be seemingly "perturbed"

  • @iannin2385
    @iannin2385 7 місяців тому

    PLEASE CONTINUE THE CHANNEL! YOUR WORK IS AMAZING, MAN.

  • @LarghettoCantabile
    @LarghettoCantabile 7 місяців тому

    Stupid musical background! How can one think adding noise enhances the signal?

  • @gytoser801
    @gytoser801 7 місяців тому

    Why cant we say dT or dV = 0 I guess because L contains both kinetic and potential energy so average height of curve is affected by each

  • @danbakana
    @danbakana 7 місяців тому

    You assumed potential and kinetic energies as vectors, but they are not. If they were, as you put it, the square of the total energy would be the sum of the squares of potential and kinetic energies, which we know is not true. Furthermore, even making this consideration, there would still be other errors. During your calculations, you assumed that the unit vector for L would be at -45°, which would only occur if kinetic and potential energies were always equal in magnitude all the time.

    • @timgerk3262
      @timgerk3262 5 місяців тому

      Since, as you say, energy is not a vector quantity, the vector sum in kinetic & potential phase space is not meaningful. 45⁰ line in phase space expresses the energy conservation constraint.

  • @krisjk999
    @krisjk999 7 місяців тому

    @14:24 I couldn’t visualize taking the signed integral of the L function and how it gives positive and negative areas wrt time axis. It looks all positive area

  • @outagas2008
    @outagas2008 7 місяців тому

    Excellent content. Hate the music.

  • @auden7560
    @auden7560 7 місяців тому

    For the rotational kinetic energy you used the moment of inertia about the cylinders center of mass. Why didn't you then apply parallel axis theorem to get the inertia about the pivot point? Since this cylinder is not rotating about its center of mass.

    • @jamesquigley4837
      @jamesquigley4837 7 місяців тому

      Good spot!

    • @omertarkkaraca842
      @omertarkkaraca842 7 місяців тому

      Due to the change in magnitude of the center of mass's location over time, inertia also changes over time

    • @auden7560
      @auden7560 7 місяців тому

      Im slightly confused as to what you are getting at. The center of mass location is dependent on time, but the magnitude of the center of mass itself is time independent, therefore the inertia about the center of mass is time independent. You may be thinking of the rotational kinetic energy term, which is time dependent due to the angular velocity component, theta dot squared. What I was pointing out was that in the video the author uses the center of mass inertia when building the lagrangian, but his object is rotating about a pivot point at the top of the cylinder, therefore he should have used parallel axis theorem to find the inertia about the pivot point.

    • @auden7560
      @auden7560 7 місяців тому

      great video by the way! Loved the animations@@jamesquigley4837

    • @efeozer6740
      @efeozer6740 7 місяців тому

      ​@@auden7560 you are right this cylinder rotates about the pivot point and this rotation is represented by using theta 1 but this cylinder also rotates with theta 2 and the rotational kinetic energy can be calculated using theta2. so using the center of mass inertia makes sense because of the change in angle theta2. You can't ignore the second theta because the system has 2 dof. Shortly, the Pivot point doesn't affect rotational velocity but the end of the spring ( top point of the cylinder) effects

  • @ruskolnikov7211
    @ruskolnikov7211 8 місяців тому

    I’ve never seen the idea L = T - V explained in any logical way. It makes the generalized coordinates make much better sense.

  • @BANKO007
    @BANKO007 8 місяців тому

    This is the ONLY explanation I've seen on UA-cam. I dont understand why others, including physics luminaries, just dump the formula on the screen and then explain algebra. This is BRILLIANT!

    • @TheDavidlloydjones
      @TheDavidlloydjones 8 місяців тому

      Agreed! I took high school physics 70 years ago, and the Newton was all we got. I've been figgering out this Lagrangian thingie bit by bit as I go along, but it's a huge relief to see it done simply and competently like this. Well done and thank you, Physics Fuency folks!

  • @Mr.Loewenzahn
    @Mr.Loewenzahn 8 місяців тому

    Wow that was mind blowing. Thank you for your work!

  • @abbeleon
    @abbeleon 8 місяців тому

    Such a satisfying payoff to visualize the eigendecomposition at the end!

  • @kylelex8814
    @kylelex8814 9 місяців тому

    What textbook did you use to learn the derivation of the Lagrangian Or did u figure it our yourself. Pls respond 🙏🏼.

  • @Akash_Saxena_2013
    @Akash_Saxena_2013 9 місяців тому

    What a deeper explanation in all 3 video on Classical Mechanics! Thank you sir to make Lagrangian approach a part of my understanding the Nature. Regards!

  • @drerichu
    @drerichu 10 місяців тому

    Thank you! I finished all three videos. The last one I had to rewind in a couple of places since there are quite a bit of calculations. These are by far the best series on Lagrangian Mechanics I can find on the internet. I understand this may be just a hobby project but the production is just unbelievable. Can't imagine how many hours you have put in creating these videos...

  • @drerichu
    @drerichu 10 місяців тому

    Beautiful, beautiful, beautiful! Thank you so much!!!

  • @eqwerewrqwerqre
    @eqwerewrqwerqre 10 місяців тому

    Extremely good description. I took "classical mechanics" last semester which actually just turned out to be an engineering dynamics course, so of course we didn't cover any of the interesting physics like gravitation into keplers laws, or lagrangian mechanics at all. We just did a bunch of stupid rube-goldberg math. Anyways, apart from that rant, now that the semester is over and grad school applications are all sent off I've been trying to teach myself the things I wasn't taught in class. I've acquired a couple classical mechanics textbooks, watched many videos, and this is the ONLY ONE that's ever motivated WHY the lagrangian is T-V. The energy space and allowed coordinates only being a single line, which can be represented by a single equation combining the two unit vectors is crazy. It make so much sense and only requires knowing you can make different coordinated spaces and knowing total energy is conserved! As well, I don't fully understand yet why the single trajectory restriction implies that the variation in the _time average_ of the lagrangian is 0. Shouldn't it just be the variation in the Lagrangian, or even just the integral of it over time? Why time average? Anyways, I've subscribed and will be watching this entire series. You have done amazing work here and I will be rewatching and taking notes on every video you make! I would love if you made more videos some day but definitely only do what you want to. Your passion for this material has made an incredible lecture and I'd be saddened to see another amazing creator run down by the algorithm. Thank you so much for your work, you have impressively contributed to the sum of human knowledge for all of us to enjoy. <3

  • @Mouse-qm8wn
    @Mouse-qm8wn 11 місяців тому

    Very great video 😊

  • @mByyurt
    @mByyurt 11 місяців тому

    Hey, where is the new one😢

    • @ChaineYTXF
      @ChaineYTXF 4 місяці тому

      He seems to have stopped. Paypal is also closed😢

  • @asklar
    @asklar 11 місяців тому

    It never made sense to me why L=T-V until I saw this video! this is the best explanation I've found!

  • @palepoint7092
    @palepoint7092 Рік тому

    We really Miss you sir 😢

    • @ChaineYTXF
      @ChaineYTXF 4 місяці тому

      May I ask if you know something? He seems to have stopped making videos and the paypal appears closed..😮