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Deriving Lagrange's Equations

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Good Vibrations with Freeball

Good Vibrations with Freeball

Күн бұрын

Deriving Lagrange's Equations using Hamilton's Principle. Demonstrating how to incorporate the effects of damping and non-conservative forces into Lagrange's equations.
Download notes for THIS video HERE: bit.ly/2KdBjRo
Download notes for my other videos: bit.ly/37OH9lX

Пікірлер: 41
@paulboughosn6174
@paulboughosn6174 3 жыл бұрын
I opened this video just to say thank you !! I wish I had a professor like you... my professor opens the pdf document and start talking for hours.....
@wduandy
@wduandy 3 жыл бұрын
You're the man!!!! Please keep doing content for youtube! Your job it's amazing!
@dmosabel07
@dmosabel07 3 жыл бұрын
You, good Sir, are heaven sent! Thank you so much!
@wangji6247
@wangji6247 3 жыл бұрын
Thank you very much for those lectures. What your are doing is just amazing. I'm trying to build my own FEM software with python in back-end and you did everything I need as fundamental.
@stitaswain7349
@stitaswain7349 2 жыл бұрын
Hi...Your teaching has helped me a lot in understanding the basics with such clarity. Request you to upload a video on Kane's method for deriving the equations of motion. It will mean a lot.
@Freeball99
@Freeball99 2 жыл бұрын
Thank for this suggestion. I have some other videos to make first, but would be happy to make a video on Kane's Method in the future.
@neyhmor
@neyhmor 3 жыл бұрын
That's one of the best explanations I've seen in a long long time. Thank you very mich sir! Would you mind if I show/link it to my Students?
@Freeball99
@Freeball99 3 жыл бұрын
Go for it. That's what they're for.
@fcvgarcia
@fcvgarcia 7 ай бұрын
Thank you very much for sharing, sir!
@Freeball99
@Freeball99 7 ай бұрын
My pleasure!
@ramazansubas1684
@ramazansubas1684 Ай бұрын
Hello dear teacher, could you please make this valuable video available as subtitled videos? It says "Currently, summarization is only available for videos with subtitles."
@Freeball99
@Freeball99 Ай бұрын
I'm not sure what the problem is here. For some reason KZfaq seems unable to auto-generate the transcript for this video like it has done for all the other videos, which is strange because the audio seems fine. I have now used a 3rd party service to successfully produce a transcript for this video and I uploaded that, but it is still not showing up. I'll keep working at this an let you know if I manage to fix it.
@lanimulrepus
@lanimulrepus 6 ай бұрын
Outstanding video...
@burakguclu3380
@burakguclu3380 3 жыл бұрын
Thank you sir! Could you please make a video about Expansion and Enclosure theorems in Continuous Vibration?
@Freeball99
@Freeball99 3 жыл бұрын
I’m not familiar with this. Do you perhaps have some reference material?
@burakguclu3380
@burakguclu3380 3 жыл бұрын
@@Freeball99 Yes, I have. I will send some links and screenshots to your e mail
@hesammortazavi9371
@hesammortazavi9371 4 ай бұрын
why T=T(qdot, ... q....) depends on q? I thought kinetic energy only depends on velocity
@Freeball99
@Freeball99 4 ай бұрын
Yes, the kinetic energy can depend on both the velocity AND position, in general. This comes up often in rotating system, for example the elastic pendulum kzfaq.info/get/bejne/n7t8lJxylZauoHU.htmlsi=CAZUfbyWsu-joQsY&t=153
@hesammortazavi9371
@hesammortazavi9371 4 ай бұрын
@@Freeball99 Thank you
@josuelima5033
@josuelima5033 Ай бұрын
What exactly the gamma constant (11:31) is? Is there any math relation for it? I'm currently developing a research paper on the structural dynamics of a cantilever beam, and your playlist with the derivations has been essential for my studies. If you could also tell me your references, it would help a lot. Thank you in advance!
@Freeball99
@Freeball99 Ай бұрын
γ is a coefficient that quantifies the extent of damping relative to the internal elastic forces. This is a quantity that is typically determined in the lab and is a function of the material of the beam, its geometry and the boundary conditions and the type of excitation. Typical values range from about 0.01 to 0.1. The specific reference I used for the is "Dynamics of Structures" by Hurty & Rubinstein. The book is long since out of print, but you can find a copy at archive.org. Not sure how helpful you'll find it though. For a reference on variational principles, my go-to reference is "Structural Dynamics: A Variational Approach" by Dym & Shames which is an excellent book! You'll likely also find an archived copy somewhere online.
@josuelima5033
@josuelima5033 Ай бұрын
@@Freeball99 thank you very much sir! i'll keep watching
@carlosquisihualpa7105
@carlosquisihualpa7105 Жыл бұрын
Hello, good video, one question, what application did you use for the video?
@Freeball99
@Freeball99 Жыл бұрын
The app is called "Paper" by WeTransfer. Running on an iPad Pro 13 inch and using an Apple Pencil.
@andrerossa8553
@andrerossa8553 2 жыл бұрын
Excellent! Tks a lot
@bayyilmaz61
@bayyilmaz61 3 жыл бұрын
Thank youuu
@YashKumar-qs2bp
@YashKumar-qs2bp 10 ай бұрын
this lagrangian equation which is eqn 16 in the video, is derived from using hamilton principle, right! But what about lagrangia equation using D'Alembert principle....coz I'm little bit confused between lagrangian eqution from hamilton principle and d'alembert principle. please solve my query asap.!!!!!
@YashKumar-qs2bp
@YashKumar-qs2bp 10 ай бұрын
hello Sir, please help me out of this query as soon as possible!!!!!
@Freeball99
@Freeball99 10 ай бұрын
Sorry for the delayed response, but I missed your comments until now... Both methods will yield the same equations of motion for systems where they are applicable, but they offer different perspectives and may be more convenient for different kinds of problems. Hamilton's Principle was discovered about 100 years after the concept of the Lagrangian. Originally, d'Alembert's Principle was used to derive the Euler-Lagrange equation, but both lead you to the same result? Hamilton's Principle is generally more abstract and is based on the concept of minimizing action. It often applies in a broader context, including fields beyond classical mechanics. d'Alembert's Principle is more intuitive and directly connected to the forces in the problem. It is particularly useful when dealing with non-conservative forces.
@FaikFatihKorkmaz
@FaikFatihKorkmaz 3 жыл бұрын
Thank you. Which software have you used to prepare slides?
@Freeball99
@Freeball99 3 жыл бұрын
The app is called "Paper" by WeTransfer. Running on an iPad Pro 13 inch and using an Apple Pencil.
@bonajab
@bonajab Жыл бұрын
I gather that the damping forces can be internal and external. Or are they all external? That's the only point I am confused about.
@Freeball99
@Freeball99 Жыл бұрын
It depends on the type of damping that you have, but usually you can model a damping force as external if you're unsure. Viscous damping can be treated as either.
@navsquid32
@navsquid32 Жыл бұрын
How can substituting the the Lagrangian into equation 11 result in Laplace's equation, seeing how there's no time derivative term for the potential energy? Seems like there isn't a way to get to d/dt(dL/dq_dot).
@Freeball99
@Freeball99 Жыл бұрын
The time derivative of the potential energy with respect to q_dot will just be zero, so only the kinetic energy will contribute to the first term of equation 13. Also, in many problems, the kinetic energy will not be depend directly on the generalized coordinate, q, and so, in that case, the kinetic energy would have zero contribution to the second term of equation 13. Therefore, this is not a problem and it allows us to write Lagrange's equation is the compact form shown in 13.
@jeffreyhowarth7850
@jeffreyhowarth7850 2 жыл бұрын
At 6:06 is the top equation is a Laplace and the bottom equation is a Poisson. Am I wrong?
@Freeball99
@Freeball99 2 жыл бұрын
No, these are not Laplacian operators. The Laplacian operator represents the divergence squared which is not what appears in either of these equations. Also, Laplace's equation typically deals with an equilibrium state (so no time dependency) while these equations are time-dependent.
@ahmedibrahim4412
@ahmedibrahim4412 3 жыл бұрын
Hello sir, What is meant by virtual displacement?
@Freeball99
@Freeball99 3 жыл бұрын
A virtual displacement means displacing the object/surface by an infinitesimal amount - it's the same idea as taking the variation of the path. This is similar to considering differential slices of objects when studying differential calculus.
@sudenur1970
@sudenur1970 Жыл бұрын
04.30 why derivative of qi is zero? i couldn't understand
@Freeball99
@Freeball99 Жыл бұрын
This goes back to an earlier video on Variational Calculus, this is the equivalent of the boundary condition ...the idea is that because we know the state of the system at times t1 and t2, therefore the variation at each of the end-points of the path is zero. In other words, this conditions says that when considering an optimal path from t1 to t2, all trial paths must be constrained to have the same beginning and ending points as the original path.
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