@0celo7 Googling "Bohr stripping criterion" strongly suggests to me that it is not "inertia" that strips off electron, but shooting the to-be-ionized particle into some kind of matter, where the outer electrons then are stripped off by interactions with the matter because they are weakly bound.
TL;DR: post examples of current questions which are edge cases for the new policy, look through the list, and vote answers up if you think they should be on topic or down if you think they should be off topic.
When we last left the ongoing examination of our homework policy, the community ha...
@0celo7 at least in the US, first-name address is very common in academia, whenever the relationship is closer than that of a typical undergrad student and their instructor.
@0celo7 That's not an answer. What is your definition of a function? (The arrows in category theory are explicitly not functions, you can't feed arguments to them)
@0celo7 No, the reason we need the "relation definition" of a function is that there are subtleties to the existence of function even if we can write down the "assignment rule", cf. e.g. existence of choice functions.
@DavidZ Go through the list of closed homework questions and see what they ask. Things like "I'm launching a projectile and..." or basic Ideal Gas Law stuff. I want to say "look at the FAQ first, come back if you still don't understand"
But this is the way many sites handle the problem of newbies: put up an FAQ and direct newbies to it. Say "read this, take two asprin [sic] and come back if you still have issues"
@DavidZ OK, I'll also propose the general topic that seems to have come up in meta: best way to handle people who want homework help. Pointing them to that list of resources would be a good "canonical" thing to do.
@barrycarter We have such a list on meta already. When we rephrase the close reasons at the end of reforming the policy, we could put a link to it in the close reason.
@ACuriousMind I was actually not aware of that link, thanks. That's more "meta" information about the site, I meant an actual list of questions. When people "ask question", maybe a link to frequently asked physics questions?
@ACuriousMind I realize most SE sites have a "FAQ" in the sense that you can look at the most frequently closed questions for duplicates, but you can hardly expect newbies to find that.
@barrycarter Oh, you already get a bunch of "similar questions" when you type in a question. They're actually quite useful if you take the time to read through them. Many people asking obvious duplicates just don't seem to do that
Is there any value in problem solving skills that we learn by solving textbook problems while learning physics? Do those skills alone carry any value to a person who hires you?
@barrycarter I would have been very annoyed if I had had to read through some physics FAQs before asking my first question here because I was pretty sure it's not a frequently asked question :P
And now I'll be off for some time, I have to cook some food
@JohnRennie I edited my question. It seems like no choice of t=0 yields the transformation I seek. I realize that wasn't exactly what your comment answered, but it's sort of related.
Maybe not so much "lead" as "prompt the discussion" - the idea being that since the topic is your idea, you're likely to be more prepared with ideas and questions than anyone else
@barrycarter there's nothing sacred about the Lorentz transformations. They are a special case where the transformation is between two inertial frames. They won't tell you anything useful if one or both frames is accelerated.
OK, now a personal question not limited to physics.SE. I tend to comment-answer a lot of questions, because I feel unworthy of actually answering. However, this means I don't get notifications when people update/comment on the question. I can star the question but that doesn't really help. Aside from answering more and commenting less, is there a solution?
@JohnRennie OK, but we agree that before I accelerate and after I'm done accelerating, I'm in an inertial frame, right?
I actually thought (seriously) that mainland China's connection to the Internet was fairly limited, and that they didn't interact much with other countries (except for Hong Kong, which is special).
user116211
@DavidZ: Thanks for the inclusion of bot in the agenda.... let's see what happens.
@barrycarter correct. But to expect the Lorentz transformation of (-10,-10) to do anything useful is futile. If the twin had been moving at -0.8c forever, i.e. had never accelerated, then they would have been at the transformed point (-30,-30).
However they did change frames so the transform leads to a frame they weren't in at the time.
@JohnRennie OK, that almost makes sense. Let's make it easier. One guy remains stationary, the other guy's been moving at 0.8 c the whole time. When they pass, they synchronize to t=0. Can that be done?
@JohnRennie Sorry, I'm creating a third "twin". This one remains 10 light years away from Earth always and forever. I want to synch times when the traveling triplet passes HIM.
OK. I assume you want a way for the travelling twin to synchronise clocks with Earth even when they are 10 lyrs away. Yes, having a third observer is a way to do this.
@JohnRennie True, good point. But I'm hoping I don't need that for the problem. What I'm saying is: when the never moving twin sees Earth at year 2000, he assigns it coordinates (-10, -10), right?
When the forever traveling twin passes him, what coordinates does he assign Earth at the year 2000?
Let's be cautious with that sees word. The 10lyr observer working in his coodinate system assigns Earth the spacetime position (-10,-10) when his position is (-10,0).
But the coordinate system of the 10lyr observer is the same as Earth apart from adding 10 to all the x values. Why introduce a third coordinate system?
@JohnRennie Oh, I think of never moving twin as my primary observer, but we don't have to. You want to make Earth the observer and have the never moving twin at (10, 0)?
No. The LT from Earth to travelling twin of (-10,-10) is (-30,-30) - actually I haven't checked that but you claim it's true - so the LT from the travelling twin to Earth of (-30,-30) will be (-10,-10).
And the LT from the travelling twin to Earth of (-10,-10) will be (-6,-6). Likewise the point (-6,-6) in the earth fraem transforms to (-10,-10) in the twin frame.
@JohnRennie in your answer http://physics.stackexchange.com/questions/190124/deriving-escape-velocity-using-centripetal-force?answertab=active#tab-top can you tell me why total energy has to be zero at infinity?
@ramsay It's conventional to define the potential energy as zero at infinity. So when you see the equation for the Newtonian potential energy $U = -GMm/r$ this implicitly assumes the energy is zero at infinity.
Describe things to me in the Earth frame. Are you saying you have the traveling twin (TT) moving towards Earth at v = -0.8c$ and the TT passes through the point (-10,-10)? So they meet at (2.5,0) i.e. 12 years later?
@JohnRennie Let me back up one step. Do you agree that, at some point in this problem, we need a transform from (-10,-10) to (-6,-6). I believe you said that yourself above earlier. And I'll even allow you to flip signs on either 10 and either 6.
I know people have exchanges for virtual currencies, but never seen one for something that is completely worthless.
@JohnRennie Revisionist! So, just to confirm (and not in a bad way), you retract your earlier comment?
The sheer pointlessness of creating a non-monetary underground exchange for worthless currency... excites me.
@JohnRennie OK, never moving twin is 10 ly from Earth at the year 2010. He asks "at what coords did light leave Earth in the year 2000?". Do we agree the answer to this is (-10,-10)?
@barrycarter if I may offer an outsider's perspective, I don't think "retract" is a very useful word to be using in a discussion like this. When you talk about retracting, whatever your intentions, it basically limits the other person to two options: either they retract their earlier statement, thereby implicitly marking it as wrong, or they don't, which implicitly limits their ability to clarify and refine it.
@JohnRennie I'm claiming that 1) a Lorentz transform from (-10,-10) to (-6,-6) must appear somewhere in this problem, and, 2) in contradiction, no such transform can appear.
@JohnRennie Sort of, but we can ignore that for now. Just focus on assigned times, not eyeball times.
@barrycarter Yeah, I'm not saying it was offensive or inappropriate or anything. Just saying it seems to push discussions in a direction that makes it less likely to end with everyone agreeing on something.
TL;DR: post examples of current questions which are edge cases for the new policy, look through the list, and vote answers up if you think they should be on topic or down if you think they should be off topic.
When we last left the ongoing examination of our homework policy, the community ha...
