Optimal technique to tear perforated paper along the perforation

Here we have a question which is considered to be off topic by some members of the community, but on topic by others (as evidenced by the fact that they answered it). I'm not entirely sure which camp I'm in. At first, I thought it was off topic, but I've been closing a lot of questions recently and since at the time, nobody else objected to the question, I thought I would give it a chance. (Besides, there is physics involved in paper tearing at some level.) However, now it's clear that there are people who consider this sort of question unambiguously off topic, and in many cases I'm inclined to agree with them. So we should make a decision.

Questions about practical phenomena that don't address the underlying reasons: on topic or off topic?

Related meta questions:

Other examples of these practical questions (all the ones I could find happen to be closed, but I think there are others out there that weren't; please comment or edit in links if you find them):

  • $\begingroup$ I don't think there is any unambiguous answer as to what questions must always be closed. At best there can be guidelines and the judgement of the community. Those seem to be working fine for now, unless you've noticed an egregious breach in the firewalls. $\endgroup$
    – Deepak Vaid
    Commented Apr 9, 2011 at 4:02
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    $\begingroup$ If How Stuff Works (about to enter private beta) makes it, I'd suggest migration over there for some of these questions. $\endgroup$ Commented Apr 12, 2011 at 13:08

2 Answers 2


I'm in favor of closing practical questions and asking them to be rephrased as physics questions.

I think the key is that with the questions you cited, the asker wanted to know something along the lines of "what's the best way to..." This elicits practical, non-physics answers (the answers to the paper-tearing question simply talk about things like running pencils along a crease; they don't have significant physics content).

These questions, slightly modified but about the same topic, could read "Why does such and such act this way...". If the paper question were phrased "Does the angle you tear paper have an effect, and why?", it would elicit more physics-based answers.

As another example, I think the question about why dust sticks to fans is a fine question, but if it had been asked, "What's the best way to keep my fan from accumulating dust?", it would be off-topic.


I say burn them from orbit -- completely off topic. :-)

I would say that questions should be strictly about Physics, not the "general physical world".

The risk is that we will end up with questions potentially overlapping with half of the other StackExchange sites!

Off the top of my head these sites as of today would overlap with those kinds of questions:

  • Motor Vehicle Maintenance and Repair ("How does a car engine work?")
  • Fitness and Nutrition ("How are food calories measured?")
  • Skeptics
  • Quantitative Finance ("The Concepts of Path Integral in Quantitative Finance")
  • Guitars ("How do I calculate string tension for a baritone guitar?")
  • Audio Recording and Production ("How does a loudspeaker work?")
  • Bicycles
  • Photography
  • Cooking

Don't get me wrong, some of these questions hold some interest (fun!) for this community. They just belong somewhere else, where they probably will receive far better answers. Ultimately we need to have a very clear and explicit "scope" so we can be a focused Q&A site of physicists for physicists.

Burn from orbit http://www.digital-digest.com/blog/DVDGuy/wp-content/uploads/2010/09/low_orbit_ion_cannon.jpg

  • $\begingroup$ Wow, my first foray into asking a question on this site and I'm not only shot down, I'm burned from a low orbit ion cannon. Way to foster community, great job! :) $\endgroup$ Commented Apr 9, 2011 at 5:33
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    $\begingroup$ +1 for ``I would say that questions should be strictly about Physics, not the "general physical world".'' $\endgroup$
    – nibot
    Commented Apr 9, 2011 at 7:54
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    $\begingroup$ @infinities PHYSICS WAS DEPLOYED! Isn't that what you asked for? Lots of .. physics? :) $\endgroup$ Commented Apr 12, 2011 at 0:37
  • $\begingroup$ @Jeff Touché -- +1 for that. ;P Next time I'll be sure and exclude Ion cannons specifically, even if they are exceptional at tearing paper. $\endgroup$ Commented Apr 12, 2011 at 3:34
  • $\begingroup$ lol :-) @InfinitiesLoop, sorry about the harsh reaction. Although your question was a little off topic, there wasn't anything particularly bad about it. It's just that we've had several questions of that type and we had never really decided as a community whether they belong on this site or not. Yours just happened to be the one that sparked the discussion. $\endgroup$
    – David Z
    Commented Apr 12, 2011 at 16:41
  • $\begingroup$ I'm honored to suffer from an Ion Cannon. I can cross that off my geek bucket list now. And in the future I'll be sure to word my question more physics-like.. that is what I was after. Thanks :P $\endgroup$ Commented Apr 14, 2011 at 14:58
  • $\begingroup$ I mean, for normal questions, I might just say nuke it from orbit... ;-) $\endgroup$
    – Sklivvz
    Commented Apr 14, 2011 at 15:19

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