• Physics Discussion
    973 replies, posted
Been toying around with an idea lately that one of my professors told me gives a much more satisfying explanation for things than current explanations (string theory, loop quantum gravity, etc) attempt to. Gotta try and see if it's compatible with... well, the rest of physics now.
What is it? [editline]11th January 2015[/editline] Also, has anyone seen an explicit derivation of the Klein-Gordon equation in momentum space? Peskin and Schroeder and Tong's notes just write down the KG equation in position space, what the Fourier transform is, and then the answer. I'm not seeing how the perform the calculation explicitly.
[QUOTE=JohnnyMo1;46904338]What is it? [editline]11th January 2015[/editline] Also, has anyone seen an explicit derivation of the Klein-Gordon equation in momentum space? Peskin and Schroeder and Tong's notes just write down the KG equation in position space, what the Fourier transform is, and then the answer. I'm not seeing how the perform the calculation explicitly.[/QUOTE] I don't really know if I want to say because if it is anything it could go somewhere big (I mean, it's probably not, but on the off chance). Suffice it to say, if it's going anywhere we've missed something [I]big[/I] and it's been staring us in the face the entire time. Incidentally, I was told to look to the Klein-Gordon equation to check if the implications for relativistic quantum mechanics check out should this highly speculative theory be correct.
Anyone ever used [URL="http://www.amazon.com/Physics-2-David-Halliday/dp/0471401943/ref=sr_1_3?s=books&ie=UTF8&qid=1421037101&sr=1-3&keywords=Physics%2C+Vol+2%2C+by+Halliday%2C+Resnick%2C+Krane"]this book[/URL] for E&M? The book [URL="http://www.amazon.com/Ideas-That-Shaped-Physics-Electromagnetic/dp/0073540994/ref=sr_1_1?s=books&ie=UTF8&qid=1421037122&sr=1-1&keywords=six+ideas+unit+e"]we were assigned [/URL]as required is just awful and while attempting the first homework assignment (due Wednesday, should have started the first day...) I wanted to punch a wall. Probably getting the Purcell E&M book as well The Six Ideas series was great imo for mechanics (and has rave reviews for relativity) but god it is so shitty for E&M so far, he just about tosses you into the deepest deep end possible. The difference between examples given and the questions is not even funny.
Are there any good online courses/resources for learning more advanced physics (post-high school)? Wont be graduating sooner than December 2015 from my current line of education.
[QUOTE=paindoc;46908535]Anyone ever used [URL="http://www.amazon.com/Physics-2-David-Halliday/dp/0471401943/ref=sr_1_3?s=books&ie=UTF8&qid=1421037101&sr=1-3&keywords=Physics%2C+Vol+2%2C+by+Halliday%2C+Resnick%2C+Krane"]this book[/URL] for E&M? The book [URL="http://www.amazon.com/Ideas-That-Shaped-Physics-Electromagnetic/dp/0073540994/ref=sr_1_1?s=books&ie=UTF8&qid=1421037122&sr=1-1&keywords=six+ideas+unit+e"]we were assigned [/URL]as required is just awful and while attempting the first homework assignment (due Wednesday, should have started the first day...) I wanted to punch a wall. Probably getting the Purcell E&M book as well The Six Ideas series was great imo for mechanics (and has rave reviews for relativity) but god it is so shitty for E&M so far, he just about tosses you into the deepest deep end possible. The difference between examples given and the questions is not even funny.[/QUOTE] I liked Griffiths (Introduction to Electrodynamics), it also has some solved examples.
[QUOTE=Number-41;46910153]I liked Griffiths (Introduction to Electrodynamics), it also has some solved examples.[/QUOTE] Griffiths electro and quantum books are both fairly good. Too bad my quantum copy is a dodgy Indian copy with half of the pages not glued in. Might try and find a hard back copy at some point. On the note of books I just had a few books arrive lately, actually. - Spacetime and Geometry: An Introduction to General Relativity - Sean M. Carroll - A General Relativity Workbook - Thomas A. Moore (this thing is fucking fantastic; you can basically teach yourself basic GR with it alone) - Theoretical Physics - Georg Joos (Dover Publications reprint) I'm only just now, a month or two after my bachelors finished (and a month before my honours year begins) really getting into the habit of buying text books. In the past I tried to avoid it wherever necessary due to how damn expensive they were, but there's just no substitute for a good, physical text book and now that I know where to get cheap copies I want to buy all of them.
[QUOTE=sltungle;46916474]Griffiths electro and quantum books are both fairly good. Too bad my quantum copy is a dodgy Indian copy with half of the pages not glued in. Might try and find a hard back copy at some point. On the note of books I just had a few books arrive lately, actually. - Spacetime and Geometry: An Introduction to General Relativity - Sean M. Carroll - A General Relativity Workbook - Thomas A. Moore (this thing is fucking fantastic; you can basically teach yourself basic GR with it alone) - Theoretical Physics - Georg Joos (Dover Publications reprint) I'm only just now, a month or two after my bachelors finished (and a month before my honours year begins) really getting into the habit of buying text books. In the past I tried to avoid it wherever necessary due to how damn expensive they were, but there's just no substitute for a good, physical text book and now that I know where to get cheap copies I want to buy all of them.[/QUOTE] Thomas A. Moore is who wrote my official coursebooks, and I really do like him for everything except Electromagnetism. His mechanics books (Six Ideas That Shaped Physics Units N and C) are great. Unit E sucks so far, but Unit R (Relativity) has rave reviews [editline]13th January 2015[/editline] also yeah physical books have no substitute but damn they are expensive
[QUOTE=paindoc;46916535]Thomas A. Moore is who wrote my official coursebooks, and I really do like him for everything except Electromagnetism. His mechanics books (Six Ideas That Shaped Physics Units N and C) are great. Unit E sucks so far, but Unit R (Relativity) has rave reviews [editline]13th January 2015[/editline] also yeah physical books have no substitute but damn they are expensive[/QUOTE] Electromag is notoriously difficult to teach anyway. It's way more difficult than any other area of physics (baring stuff like string theory, but I don't know enough to comment to be honest) as far as I'm concerned (most everybody at my uni agrees, too - professors included).. I use [URL="http://www.bookdepository.com/"]Book Depository[/URL] to get good prices on books now. Abebooks also has good prices too, but they're where I got my dodgy Griffiths copy from (and a softcover copy of Introductory Nuclear Physics by Krane when I ordered a hardcover copy) so I normally give them a miss now.
[QUOTE=sltungle;46916578]Electromag is notoriously difficult to teach anyway. It's way more difficult than any other area of physics (baring stuff like string theory, but I don't know enough to comment to be honest) as far as I'm concerned (most everybody at my uni agrees, too - professors included).. I use [URL="http://www.bookdepository.com/"]Book Depository[/URL] to get good prices on books now. Abebooks also has good prices too, but they're where I got my dodgy Griffiths copy from (and a softcover copy of Introductory Nuclear Physics by Krane when I ordered a hardcover copy) so I normally give them a miss now.[/QUOTE] I've had more luck so far using the Griffiths for Electromag, now I just want a solutions guide so I can check my answers on the practice
Is the General Relativity Workbook something that's possible to go through with high school-level of understanding of physics?
[QUOTE=Hattiwatti;46916610]Is the General Relativity Workbook something that's possible to go through with high school-level of understanding of physics?[/QUOTE] If his other books are anything to indicate, Thomas Moore does a good job of keeping it simple. In the appendix of our mechanics textbook he had a section on calculus concepts in case that was needed too
[QUOTE=Hattiwatti;46916610]Is the General Relativity Workbook something that's possible to go through with high school-level of understanding of physics?[/QUOTE] Difficult to say. If you've done calculus then I'd say you'd probably be able to get through it; you'll just have to keep chipping at it bit by bit. I spent like two days on a single question completely stuck with this ridiculously difficult integral, then I realised I'd made a rather minor mistake in the section before, fixed it up, and did the integration in like three seconds after that. D'oh!
One of the soon-to-be Ph.D students at my uni showed me this old paper, today (it's in economics, but it reminds me of some satirical physics papers I've seen before in its delivery). The abstract is brilliant and it gave me a good laugh; [url]https://www.princeton.edu/~pkrugman/interstellar.pdf[/url] It made me want to find a satirical string theory paper I (think I) saw on here a while back, but I can't seem to find it.
Triple post, lol. In the process of writing my first ever paper; hopefully it'll be sent away for publication before I start my honours year in March. I'm quite excited! We're aiming for Phys Rev E (my supervisor only has PRE and PRC left to be published in (and PR Applied, but that's not gonna be difficult for him in the least))... funny, because being published in a statistical physics journal is the last place I ever expected to be published. At least I'm getting it out of the way, I suppose!
So I've been thinking about Mars lately, and I wondered. Could it hypothetically be possible to "kickstart" Mars' by hitting it with a giant asteroid? Melting up the core and restarting the engine.
[QUOTE=JohnnyMo1;46672264]So Walter Lewin was found to have sexually harassed an MIT student and now his famous video lectures are being taken down. [url]https://newsoffice.mit.edu/2014/lewin-courses-removed-1208[/url][/QUOTE] There's more on this in this article, although it isn't from an official source so I'd take it with a grain of salt: [url]https://www.insidehighered.com/news/2015/01/23/complainant-unprecedented-walter-lewin-sexual-harassment-case-comes-forward[/url]
I really should know this, but I don't. Help. (No friction on the hill, the projectiles sticks to the big thing, calculate the distance s in terms of r, muk, ma, mc) [IMG]http://i59.tinypic.com/153n0cl.png[/IMG]
I majored in nanotech, but I've been working in the game industry ever since I graduated... I still enjoy reading material science and biomedical papers though. Would love to do medical simulation... [QUOTE=JohanGS;47167464]I really should know this, but I don't. Help. (No friction on the hill, the projectiles sticks to the big thing, calculate the distance s in terms of r, muk, ma, mc) [IMG]http://i59.tinypic.com/153n0cl.png[/IMG][/QUOTE] Are you asking people to do homework for you? lol Answer is simple... F=ma.
[QUOTE=JohanGS;47167464]I really should know this, but I don't. Help. (No friction on the hill, the projectiles sticks to the big thing, calculate the distance s in terms of r, muk, ma, mc) [IMG]http://i59.tinypic.com/153n0cl.png[/IMG][/QUOTE] For the hill part, you've got a conservative system, the sum of kinetic and potential energy is a constant.
To find velocity of thing sliding down the hill: Use conservation of energy. To find velocity of block + thing: use conservation of momentum. To find distance it slides: use Newton + 1d kinematics.
[QUOTE=download;46603876]A number of modern CAD programs had 3D CFD addons. Can someone explain why free neutrons decay with a half-life of about 11 minutes? Why do free neutrons decay and neutrons as part of an atomic nucleus (say H-2 or He) do not?[/QUOTE] Atomic decay is caused by the weak force. Gravity pulls matters together, but is insignificant in molecular level. Electromagnetism affects electrons and protons, but does not take a role against neutrons. you can see the weak force as a force that pulls everything apart. It is the weakest force of all scaling to distace, so it only matters not affected by other forces and are very close together, less than 10^-18 meters. It causes decay or fission by affecting the spin on the quark level. Feymen diagrams for beta decay can be explained by weak force.
Didn't notice this thread before. I'm currently in the penultimate year of a theoretical physics bachelors degree. I basically just do a shitload of programming at the moment, but I'm looking into available PhD positions for when I graduate. There's one at the university I'm studying which involves quantum learning (or, the ability to measure an event without disturbing the system, effectively allowing all possible quantum states to be measured at once). Failing that, I'd be looking to do a teaching qualification as there's a distinct lack of physics teachers in UK schools.
[QUOTE=JohnnyMo1;47169242]To find velocity of thing sliding down the hill: Use conservation of energy. To find velocity of block + thing: use conservation of momentum. To find distance it slides: use Newton + 1d kinematics.[/QUOTE] I need help with the 1D kinematics though
Ff = m g mu Fnet = Fv - Ff then you use the velocity squared formula to get time independent displacement. v2^2 = v1^2 - 2 a s
[QUOTE=Maya2008;47167793]Are you asking people to do homework for you? lol Answer is simple... F=ma.[/QUOTE] The thing is that I did this in the equivalent of high school, which was four years ago. Then when I started university, the first half year was almost only math. I know about most mech stuff I read back then, but this little sliver of it I don't remember that well. tl;dr fuck off
Well... tl;dr, it is your homework. You should say it in your post explicitly so that no one will solve it out for you. You will get KICKED OUT of uni if you are caught FYI... Being a TA/assisting lecturer at uni for two years, I don't appreciate students copying solutions. There is nothing wrong with asking for approach, however.
We don't even have homework, we're given lectures and recommended tasks. That's it. Now stop being a condescending cunt.
Since when am I being condescending? oO There is nothing wrong with learning...
[QUOTE=Maya2008;47172272]Since when am I being condescending? oO There is nothing wrong with learning...[/QUOTE] I thought you were just taking the piss when you called it my homework, that's why I didn't call you out on it.
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