Physics questions are also called physics problems, puzzlers*, brain teasers, brain twisters, riddles, or challenges. Below I list some places where you can find some.
There’s no such thing as a “recreational physics question” because every physics question could be pursued recreationally, in principle. In practice, tackling some questions requires resources beyond what one person (or a small group) can do, but don’t let that discourage you: the set of physics questions that can be pursued recreationally is vast.
Of course, the range of physics questions that you can do recreationally depends on how much physics you know, but that’s true of all forms of recreation. The range of downhill ski runs that you can enjoy depends on your downhill skiing ability. The more you learn, the more fun you can have!
Sources of Physics Questions
A great source of physics questions is your own curiosity, or the curiosity of your friends, family and colleagues.
You can also find physics problems in books, journals, websites, and many other places. Below, I’ve listed some sources of questions well-suited to recreational pursuit.
Brainteaser Physics: Challenging Physics Puzzlers by Göran Grimvall
The Flying Circus of Physics by Jearl Walker. Over 700 questions. First published in 1975; the second edition was published in 2006.
Mad About Physics: Braintwisters, Paradoxes, and Curiosities by Christopher Jargodzki and Franklin Potter. They also wrote a sequel titled Mad About Modern Physics
Thinking Physics: Understandable Practical Reality by Lewis Carroll Epstein
Mrs. Perkins’s Electric Quilt: And Other Intriguing Stories of Mathematical Physics by Paul J. Nahin
Millergrams: Some Enchanting Questions for Enquiring Minds by Julius S. Miller
300 Creative Physics Problems with Solutions by László Holics
200 Puzzling Physics Problems: With Hints and Solutions by P. Gnädig, G. Honyek, K.F. Riley
The Physics Teacher and the American Journal of Physics (AJP) are peer-reviewed journals published by the American Association of Physics Teachers. They often include problems of interest to high school and undergraduate physics students. The European Journal of Physics (EJP) is similar to the AJP.
Some papers submitted to arXiv.org may be of interest, e.g. recent submissions in the category ‘Popular Physics’
Physics Q&A Websites and Forums
NEWTON Ask a Scientist and NEWTON Question of the Week are provided by Argonne National Laboratory and the US Department of Energy. NEWTON has been online since 1991. Not all questions are physics, but many are. Note: In February, 2015, Argonne announced that they would be shutting down the NEWTON website on March 1; the Internet Archive (archive.org) has an archive.
Ask the Van – Anyone can submit a physics question. The site started in 1998 and now over 6000 questions have been answered by volunteers from the Department of Physics at the University of Illinois’ Physics Van outreach program.
Physics Stack Exchange – “a question and answer site for active researchers, academics and students of physics. It’s 100% free, no registration required.”
Physics and Astronomy Ask the Experts at PhysLink.com. Ask a question, and (hopefully) get an answer from an expert.
Physics Forums (PF) at physicsforums.com
PhysForum Science, Physics and Technology Discussion Forums at physforum.com
The Physics Forum at thephysicsforum.com
Physics Blogs Which Consider Specific Physics Questions
Dot Physics – A physics blog by Rhett Allain, a physics professor.
What If? – A weekly series of short articles by Randall Munroe, the creator of xkcd. Many involve physics. There are related discussion threads on the xkcd forums. He also published a book with the same name.
Websites with Physics Questions
David Morin’s problems for undergraduates in the Harvard University Department of Physics (includes some math problems).
Physics Problems to Challenge Understanding, emphasizing concepts, and insight. A set of physics problems compiled and annotated by Donald Simanek, Emeritus Professor of Physics, Lock Haven University of Pennsylvania. His website has a lot of other recreational physics material, especially supposed perpetual motion machines, along with explanations of why they don’t work.
Physics Examples and Other Pedagogic Diversions by Professor K. McDonald of the Department of Physics at Princeton University.
* The phrase “physics puzzle” has come to mean the same thing as “physics puzzle game,” meaning a casual video game involving simulated physics. Examples include Angry Birds and Cut The Rope. I wouldn’t consider playing those games to be doing recreational physics, any more than I’d consider a basketball player to be doing recreational physics. Thinking about physics and letting physics just happen are two different things.