Classical Mechanics | Lecture 3

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1. The problem with using infinitesimals is readily seen here, in the very beginning of the lecture: a mínimum in potential energy has these two inconsistent effects: one, if you change the input just a bit, energy increases (because it was at a minimum); two, if you change the input just a bit, nothing changes, because the derivative is 0.
2. The initial transformation of coordinates is wrong too. The signs are wrong there.
   It]s lovely. It make me remember the demo and rewrite it. Thank's proffesor susskind.
   Anyway, I love you, but I desagree with your multivers theory.
3. The demo about coriolis force has many errors. 1. The last therm of the derivation is not omega * (x dot * y-y dot * x) . It is 2 * omega * (y dot * x - x dot * y). From this error it goes to the coriolis force formula where the 2 is lost and the signs are reverced. fx coriolis is 2 * m * omega * y dot. !!!!
4. Regarding the first 20min of the lecture, why variation (for both cases of function and functional) is 0 when we're at the minimum? What does it mean "the change is 0 TO THE FIRST ORDER"? What does TO FIRST ORDER means? Does it have to do with Taylor expansion? If so, how? (I don't remember basic calculus stuff well, sorry) Thanks.
5. Love the fact that this guy is a fucking Genius and don't even know how to write: "for all i" in mathematical term ! XD
6. Is the Coriolis force term correct? I think there's a factor of 2 that goes missing on the Coriolis term when he multiplies the Lagrangian out in the rotating reference frame. Can anyone confirm?
7. 1：26：48 Why =mr *(theta dot)^2- dV/dt? Is that the derivative of r?
   If is, why not r double dot instead?
   Thx
8. Must the action has exactly one stationary value?
9. I have a question: I plan to watch all these lectures by Mr Susskind on classical mechanics, but will I get anything out of these lectures without an accompanying textbook?
   
   Thanks.
10. 1 hour and 44 minutes of someone eating their lunch is just too much for me. .__. Of all the thousands of times he's given this lecture you'd think they'd record the one he's not eating through.
11. YES!! 0:40:00 to 0:44:00 is a clearer derivation of the Euler-Language equation than page 112-114 of the book, imho.
12. His rotated coordinate transformations at 1:06:10 are slightly wrong, he messed up the signs. The second term of the x transformation should be negative, and the first term of the y transformation should be positive.
    
    These are the proper transformations:
    x = Xcos(wt) - Ysin(wt)
    y = Xsin(wt) + Ycos(wt)
13. tight.
14. I can't find the answers to the exercises beyond chapter 6. Somebody?
15. 1:34 calculus of variations
    32:56 euler-lagrange equation
    51:25 lagrangian
16. He kept saying delta at minute 4-5, but what he drew wasn't delta, am i missing something or did he make a mistake?
17. i got confused at 44:40, what is he doing, first he says he differentiates with respect to xi, then he does it with respect to vi. at first he differentiates the term above, then the term below. I know the euler lagrange equation but i've never seen a "discrete" derivation of it. could somebody explain that to me?
18. Great lecture, thanks so much for sharing this. I found this very helpful and well explained.
19. why would you say that mathematical rigor is lacking? this is a physics lecture and he is trying to convey ideas. personally, i found this lecture to be very helpful. thank you very much.
20. it seems to me that he doesnt really write a lot of stuff on the board. its like im waiting for something but never get it.