Often we get questions of the form
- "How to build this particular device?" or
- "Why was this design implemented in such-and-such product?"
Are these questions appropriate for Physics Stackexchange?
What exactly is the relation between physics and engineering?
Physics is a natural science. It seeks to study how and/or why nature works the way we observe. Engineering applies our understanding of nature to specific, real-world problems, creating new devices, products, or processes to solve those problems.
While both physics and engineering often work together, using similar toolsets from mathematics, they have different goals. Put one way, physics seeks to break down the world around us into more modular parts and more fundamental relations, while engineering seeks to reassemble those pieces into a new form.
So engineering is off-topic here?
Often, yes. When constructing a product for use in the world, there are many considerations that go into the decision-making process. The underlying physical principles are only a part of this. The physics community, while often tangentially knowledgeable in these areas, is not the place to seek guidance when ease-of-use, manufacturing costs, material availabilities, etc. are also primary considerations.
Are any engineering questions allowed?
Questions inspired by engineering considerations can be on-topic on this site. For instance, it would be valid to ask if there is a fundamental physical limit to
Similarly, questions like What really allows airplanes to fly? that ask how a man-made system works are also on topic, as long as they aren't too broad. Questions about the physical reasoning and analysis that lead to design decisions are on topic; questions seeking help designing or building something is off topic.
What about experimental physics and laboratory equipment?
Physics is not just theoretical, and experimental physics is on topic here. This includes questions about the usage of laboratory equipment.
If my question doesn't belong here, where can I ask it?
There are sites that allow certain types of engineering question on the Stackexchange Network. Your question may be suitable at one of the following:
Admittedly, that list does not cover all forms of engineering. You can always propose a new Stackexchange site or support a proposal over at Area 51. For a quicker response, users with at least 20 reputation can always bring up a question in our chat room. Note that there is no guarantee that anyone there has any input, and The h Bar is not a Q&A unto itself, but still we physics enthusiasts tend to like problem solving in general, as well as interesting questions.
OK. I am an Engineering Physicist. And in my just-above-zero engineering experience, the application of Physics is of paramount importance. That being said, asking questions like "how to build this device? "should be off topic. However, questions related to engineering where questions pertain to a physical concept that has to be used, should be welcomed. After all, that is the goal of physics-making things that don't exist and improving things that exist for the good of mankind .
Graduate physics students, and postdocs, often are in the position of having to design and build their own experimental apparatus. Questions about 'engineering' experimental apparatus for research seem on-topic to me. Questions about 'engineering' something intended for commercial use seems off-topic because there are people paid to do that.
From my own (not necessary unique) experience as a 'Backyard Physicist' (note - this is not the same as 'hobbyist'), I have to make my own tools a lot of the time.
The division between applied physics and engineering, to me at least, is:
Unless a question specifically asks for the 2nd case, it should not be assumed that they are asking for it.
As another answer mentioned Engineering is Physics (use same models, same domain, same principles). i would say engineering is practical physics (associated in some part to experimental physics as well).
So engineering as practical physics is certainly on-topic on this site.
Many times, real-world examples or analogies are used in physics (they are used in mathematics for crying out loud), to make concepts more intuitive or applicable.
Problem solving is not only for engineers. Physicists (and mathematicians and other domains) actually solve problems (and i mean practical problems as well).
R. Feynman and his diagrams were considered as less than physics (actually Schwinger considered them to be engineering "..all S and T lines and rays..", reference: "Genius, the life of R. Feynman").
i'm sure some people will disagree with providing intuition and real-world analogies.
Plus i would like to mention that some sites actually forbid (explicitly or implicitly) practical questions about physics. Personally i strongly disagree with this.
The whole point is not memorisation of given rules, but actual comprehension of the why and how to the point of actual application (and even beyond).