What is the policy on asking homework questions on Physics Stack Exchange?
It's not enough to just show your work and ask where you went wrong. If you just need someone to check your work, you can always seek out a friend, classmate, or teacher. As a rule of thumb, a good conceptual question should be useful even to someone who isn't looking at the problem you happen to be working on
A "homework question" is any question whose value lies in helping you understand the method by which the question can be solved, rather than getting the answer itself. This includes not just questions from actual homework assignments, but also self-study problems, puzzles, etc.
On the other hand, questions that come up in the course of doing a homework problem, but are separate from the main point of the problem, might not be considered homework questions. There's a bit of a judgment call to be made, depending on the context of the problem. If you're not sure, it's probably safer to treat your question as a homework question and later find out that it isn't, than the other way around.
Yes, but there are a couple of things you need to make sure of first.
As a general rule, we do not discourage homework questions, as long as they are related to physics. But do keep in mind that Physics Stack Exchange is not primarily a homework help site; it's a place to get specific conceptual physics questions answered. The list in the following section will help you ask questions about your homework in a way that fits in with the site's philosophy.
Also, make sure you know whether your learning institution (middle school, high school, college, etc.) and your teacher or professor allow you to consult other people, or to post the exact question on the internet. This is usually addressed by your institution's honor code or rules and regulations, and any specific class policies. You should ask your teacher whether asking a homework question here is appropriate before posting your question.
See if an existing question helps you
Check and see if someone has already asked a question that gives you the information you need. The search box at the top right corner of the page will be pretty useful here, but you can also try looking at tags that are relevant to your question.
If you find a prior question that seems relevant but doesn't clear up your confusion, mention it when you write your own question. That gives the people answering a better idea of what kinds of explanations don't work for you, and what might be more effective.
Ask about the specific concept that gives you trouble
We expect you to narrow down the problem to the particular concept that's giving you trouble and ask about that specifically. That produces a question that is more relevant to others who might be having the same problem, as well as probably more interesting to answer. As a side effect it shows that you're not just being lazy and trying to get us to do your work for you.
The best way to produce a focused, specific question is to show your work. Explain what you've been able to figure out so far and how you did it. Showing your work will help us gauge where you are having problems: if it is a technical thing near the end, a short to the point answer will suffice; if it is some fundamental problem with understanding the subject, somebody will then write a longer, more detailed response. It will also prevent people from spending a lot of time going over ground that you have already covered or understand well already.
It's not enough to just show your work and ask where you went wrong. If you just need someone to check your work, you can always seek out a friend, classmate, or teacher. As a rule of thumb, a good conceptual question should be useful even to someone who isn't looking at the problem you happen to be working on. Of course, it's still good to include the text of your problem, just in case (more on that a few paragraphs down).
Don't just copy the exact problem from your homework assignment or textbook. In particular, when you are asking for help, writing in imperative mode ("Show that...", "Compute...", or "Prove or find a counterexample: ...") is at the very least impolite: you are, after all, trying to ask a question, not give an assignment. It also turns many people off.
Reference the source
If you're asking about a specific homework problem from a textbook, include the book and the problem number, so that someone trying to answer the question can go look it up themselves if they need to. If you're asking about a specific problem from a custom assignment prepared by the instructor, it helps if you quote the complete text of the problem in your post. Again, this shouldn't be the entire content of the post - you still need to ask about the specific issue that's confusing you, in addition to quoting the problem - but you never know when the person answering might need additional information from the original problem.
Use the homework tag
Use the homework-and-exercises tag on your question, in addition to any other tags that identify the kind of physics involved. This lets answerers know that you're looking for an answer which explains the underlying concepts.
If you don't include the tag, someone will usually add it for you. If that happens, don't think that we're accusing you of lying about whether your question is from a homework assignment! The tag is used for any question in which the point is to learn the method you're using to solve it, rather than just to get the answer.
This is pretty well covered by a discussion on the Math Stack Exchange site.
Providing an answer that doesn't help a student learn is not in the student's own best interest, and if a solution complete enough to be copied verbatim and handed in is given immediately, it will encourage more people to use the site as a free homework service. In the spirit of creating a lasting resource of mathematical knowledge, you may come back after a suitable amount of time and edit your response to include a more complete answer. Or even better, the student can post his own correct answer!
If someone posts an answer to a homework-type question that gives away a complete or near-complete solution, in most cases it will be temporarily deleted.
The rules for how to properly post homework questions can be a bit confusing, so here are some examples:
A good homework question states the problem clearly, shows an attempt to work through it, and identifies the specific issue that is giving the questioner trouble. These questions demonstrate that pretty well.
These homework questions don't show any effort put into solving the problem, and they are too specific to be of use to anybody except the person asking. That makes them inappropriate for this site.
If your question was closed as off-topic on this site, and you are unable to formulate it in the ways explained above, there are still other sites where you can ask for help. We keep a list on the thread My question was closed on Phys.SE. Can you recommend me another internet site where my question might be on-topic?.
Parts adapted from https://math.meta.stackexchange.com/questions/1803/how-to-ask-a-homework-question
Bad:
Good:
Don't forget: closing a question is mostly a subjective decision. The reviewers see a "close" and a "leave open" button next to your question. Although there are site rules, it is mainly up to them how to interpret these rules.
The aim of our site is to be an authoritative source of information for active researchers, academics and students of physics and astronomy, and we want the posts here to be interesting, informative and reliable. To this end we sometimes close questions that don’t fit with the goals of the site. This answer explains why we sometimes close questions as homework and exercises, and how you can word your question to avoid it being closed.
There are two main things we consider when deciding whether to close a question.
The first criterion is fairly obvious: the physics community isn’t going to take us seriously if there’s any perception that we help people to cheat with their course work. So if you post a question that’s obviously been copied and pasted from a homework assignment we’re going to close it immediately. We can’t read your mind, so we can’t be sure whether your question really is homework or not, but we will err on the side of caution. If your question looks like homework we will close it. If your question isn’t homework then it’s down to you to explain that in your post, which brings us to the second criterion.
The second criterion is a little more subtle and is related to our aim to be interesting and informative. As a general rule homework problems and/or worked exercises are used to reinforce something you’ve been taught. For example if you do a special relativity course you will be taught about time dilation and how to calculate it using the Lorentz transformations. Then you’ll be given endless homework problems requiring you to do basically routine calculations like finding the lifetime of atmospheric muons or whether a fast moving pole will fit in a barn.
Our view is that while the routine calculations are important this site isn’t the place for them. The problem is that (a) they are routine and (b) there are a near infinite variety of such questions, and they would swamp the site. So if you post a question that is of this type we’ll probably close it with the tag [homework-and-exercises]. That doesn’t mean we think it’s a bad question, just that this site isn’t the place for it.
If you find yourself wanting help with a homework-like question then it’s probably possible to rephrase it into a more conceptual question. For example rather than asking about the lifetime of a muon traveling at $0.99$ you could reword your question to ask how we use the Lorentz transformations to calculate time dilations.