On Mon, Nov 14, 2011 at 11:00 PM, Luke <[email protected]> wrote: > Ondrej, > Great comments! How are you!? We need to get a beer next time you > are coming through -- do you have a regular schedule, maybe Google > Calendar that we can share?
Absolutely. I don't go around regularly, but I do from time to time. Last time I left you a message, but you didn't get back to me. :) > >> 1) How did you create the drawing in the pdf? > I used TikZ. I looked into PStricks, which is very powerful, but it > seems like TikZ has a bit nicer design and is a bit higher level. But > other options include Inkscape, which can export pstricks/tikz code to > be included in your latex code. Another cool online tool is: > > http://www.geogebra.org/cms/ > > it will also let you export those formats, but gives you a nice gui > and still lets you easily change the exact values of all the > coordinates, should you want to be precise. Can you post the TikZ source? I like it a lot. > >> 2) We did this exact example in our undergrad mechanics course at my >> university using a Lagrangian to derive the equations of motion. I >> wonder if i can redo it, I would love to put this and similar examples >> into my notes at theoretical-physics.net. Also with your solution, to >> show that one can derive the equations of motion in another way. > > Yeah, Lagrange's is the way to go, I didn't do that approach for the > solution because I figured F=ma would be the "simplest" and least > likely to raise flags about "fancy math" being used. But when F = > dp/dt = ma is not allowed.... I'm not really sure what technique to > use.... Yeah. > >> 3) Can pydy derive the equation of motion? > > Definitely, although it is almost overkill :) If you have time, can you create an example for pydy for it? I think it's simple, but not *so* simple, and it would serve as a nice example for pydy. > >> 4) Feynman would of course never use your systematic approach, but >> rather use some trick to find the solution in 2 lines > > One of the perks of being Feynman, I suppose :) > >> 5) Point 4) is precisely why I don't like Feynman's approach to >> physics as a way to learn and do physical problems, but I like it as >> an amusement and to get new physical insight, *after* I have been >> able to solve the problem using a systematic approach. This is also >> the motivation behind theoretical-physics.net, to *only* use >> systematic approach and reject all "tricks". > > Yeah, whenever I hear the word "trick", I get a little uneasy. Cass > said she might remember having seen a "trick" for this problem, but > couldn't find it or remember it. I don't want to memorize a bunch of > "tricks", I want to know a few key principles and concepts and be able > to apply them to lots of different problems. I agree though, after > you understand something, it is nice to see the shortcut. Exactly. > >> 6) If anyone finds the trick to solve the problem, I would be interested. > > I'll let you know. I sent it out to a bunch of physicists and > engineers here at UCD and haven't heard any ideas from any of them. Awesome. Ondrej -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
