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- Comments are encouraged, so there are no restrictions on who can leave a comment, though comments
*are *moderated, and you’ll need to leave your name and an email address (the email address won’t be published) since there is a lot of spam out there.
- Because of WordPress’s spam filter, some genuine comments may get deleted without me seeing them. I have the spam filter set to its most aggressive level (that is, it will delete anything it thinks is spam, and this blog gets hundreds of spam comments every day). If you really want your comment to show up, try rewording it and make sure it doesn’t have a lot of links in it (and don’t mention things like viagra!).
**If you want to use mathematics in your comment** and know a bit of Latex, you can get the math to show up properly by using wordpress’s Latex format, described here. If you want the math’s background colour to blend in with the background of the comments section, add &bg=e5e4e8 before the final $ sign in your Latex code (see the ‘Latex colors’ section of the wordpress documentation).
**Please use equation numbers **if you are asking about a particular equation in a post. It really helps me understand exactly what you’re asking. (As I wrote many of these posts several years ago, their contents are not always fresh in my mind!)
- I’ll try to answer comments that point out errors in a post, or that ask for clarification of a point made in a post, as soon as I can.
- Please note that due to time limitations (and often lack of knowledge), I usually won’t answer comments except those pointing out errors in a post, though I will approve your comment so that others may reply to your question.
- Comments asking for solutions to problems that are not currently posted will be ignored. Sorry, but I’m working at my own pace through the books I’ve selected (which usually means the books I can (mostly) understand), so I can’t accept requests to solve problems for you.
- Physicspages is strictly a one-man project, so I don’t accept articles from anyone else, and I don’t allow administrator access to the blog for anyone but myself.

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JonOut of interest how do you enable TeX on your comments? Using MathJax?

gwrowePost authorI use the WP Latex plugin in WordPress.

Pradnyahi,

any material on earth as a free symmetric top. especially space cone and body cone, in your way of teaching.

btw thnx for these pages, they are really helpful.

PhilHello, do you have any tips in general on how to study for physics? I’m currently doing my degree and would be interested in how to get better at it!

gwrowePost authorThat’s a big question and I’m not sure I’m very qualified to answer it, but I’ll throw out a few ideas.

First, one thing that often isn’t emphasized or made clear in textbooks or in university courses is the distinction between physical ideas that are postulated or inferred from experiments and results that are derived from these postulates. In other words, it’s important to distinguish between the physics and the mathematics when trying to understand a topic in physics. For example, in special relativity, the physics is contained in Einstein’s postulates that all laws must look the same in all inertial frames and that the speed of light is a universal constant. All the other results in special relativity (length contraction, time dilation and so on) are derived mathematically from those two postulates. In classical electromagnetism, the basic ‘laws’ such as Gauss’s law, Ampère’s law, Faraday’s law and even, ultimately, Maxwell’s equations are essentially postulated laws based on experiment, and not something derived mathematically from some more primitive result. (In fact, some books like Feynman’s lectures just state Maxwell’s equations as the starting point for classical electrodynamics.) In quantum mechanics, Schrödinger’s equation can be regarded as a postulate and can again be simply stated at the start of a textbook (as Griffiths does). And so on. It took me a long time before it dawned on me that to understand physical theories you just had to accept their postulates and go from there.

On a more practical level, once you’re read about or been taught the fundamental ideas in a physical theory, it’s very important to do as many problems as you can. By ‘do problems’ I mean to really give them a solid attempt before seeking help on the web (in sites like physicspages) or even in textbooks. Doing problems has two main benefits: it helps ensure you really do understand the physical theory required to solve the problem, and it develops your skills at reasoning and mathematics.

You also need the willingness to just stick with it until you understand the theory or solve the problem. One technique that can help avoid banging one’s head against the wall in frustration is the practice of lateral thinking. If you’re trying to understand something or solve a problem and it’s just not working for you, take a step back and examine the techniques you’re using. Try to think of another way of approaching the problem rather than repeatedly trying the same method over and over and getting nowhere. [Having said that, however, if your problem involves a lot of algebra, it

isworth checking your work in detail as often a dropped minus sign or misplaced factor of can make all the difference.]Finally, while a good textbook on a physics topic is essential, Google is your friend as well. The internet is an enormous advantage that students in my day (the 1970s) didn’t have. If there is a topic that confuses you because your textbook or lecturer hasn’t made something clear, by all means google it and get as many different points of view on that topic as you can. What works for one student often confuses the hell out of another, so keep looking until you find an explanation that makes sense. My posts in physicspages are the result of my working through textbooks, but in many cases I’ve gone the google route until I’ve found an explanation that worked for me and then rewritten it in a way that is clear to me (and hopefully to a few others out there).

I hope that helps. Best wishes for your study of physics. It is, in my humble opinion, the greatest academic subject in existence and well worth the effort you put into it.

Arindam kumar chatterjeeThis blog is excellent……

roorkee collegeIt is very interesting content and explained nicely.