I am trying to determine the g-force acting on a certain human joint (knee, elbow, etc..). I do not have the mass of the joint just its acceleration that i get from watching its position change over time. I found this website that shows a formula that does not require me to know the mass (mpgh.net/forum/270-homework-learning-section/… ).

The answer on that site does say that i need the vector sum of the acceleration, and the example involves an astronaut in space so im not sure i can use that answer. Do i have enough information in just point locations over time to determine the g-forces acting on it?

@ManishEarth: I thought of sharing my blog at Tavern :)

I am assuming a yes on all of this? :o

@ManishEarth: Can you give me a link to the site (regarding that image you posted)..?

I suspect it's quora :)

Okay... I got it :D

@Gugg: Permissions to use your quote in my blog... (I'm gonna use it anyway)

@ChrisWhite Whyever not, though? We're taught a bit of qm-y concepts like basic wave particle duality (de Broglie, Bohr atom, etc) at high school level. I think that exists in the States too.

Or is that only for AP?

@CrazyBuddy Permission denied. Which quote?

@Gugg How dare you say that to me? :P

@CrazyBuddy No guts, no glory. Permission granted, as long as you don't attribute.

@Gugg Well, I'll link to your chat transcript then :)

@CrazyBuddy That's even worse. :)

@Gugg Hey... You'd gain reputation (Ugh... Not score...!!!!) :P

People (does anyone read your blog?) might think I am a physicist.

@Gugg I've just started it now... So, apparently no one would :D

@Gugg They've mistakenly assumed me, so why not you? o.O

On topic on both sites (I think); anyone wants to answer it?

@chriswhite Being our resident specialist of visible-light and stars, it's perfectly in your domain :>

@ManishEarth if you use @ here, will it appears in their inbox? btw, there are many chris here

@hwlau what..??

@hwl If a user has been around recently but is currently not in the room, then yes. After a 15minute delay

@ManishEarth Did you see my ping to Gugg...??

@ManishEarth but how about if there is name ambiguity?

He wasn't active in the room for more than 2 days... :)

But, it worked..

Easy... Just load older messages till you see Gugg's msg, and do the ping...

how do you know?

@hwl everyone gets pinged

=.=

Just like in comments. You only need >=3 letters to ping. Ambiguities ping everyone. Though I think it resolves ambiguities when a space is involved

@crazy that just makes autocomplete work. Autocomplete != ping

I forgot the exact ping time limit

However message replying and superpinging always work.

@ManishEarth what is superpinging? how or use

found, why there is so many strange terms in SE

@CrazyBuddy What's your blog for? What purpose do you have in mind?

@ManishEarth Ahh...

@Gugg I always wanted to express what's in my mind... (evaluate myself) ;-)

@CrazyBuddy So, it's like a diary of sorts?

@Gugg I s a blog really need a purpose?

@hwlau Nope... not at all :)

@hwlau Obviously, yes. There are opportunity costs.

@Gugg Not a private diary though.... I'll write what I like to share...

My knowledge of something... sorta :D

(mostly basically physics) But, don't expect much... It won't be useful to Physics.SE people :)

Are you intent on commenting on Physics SE only?

@Gugg Huh?

@hwlau hello

Or will you also discuss, e.g., geopolitical issues?

Do a bit of ranting, perhaps?

@Gugg Hey... I'm not that kind :D

@Gugg I already did one :P

Do we have to talk physics here? I just saw Tinker Tailor Soldier Spy and I thought it was astonishingly superb. But maybe it was particularly the choice of closing song.

@Gugg Nah... We don't usually talk Physics here...

Chat rooms go "off-topic" often ;-)

@CrazyBuddy If you'd blog about this movie and the era it depicts, I'd really love to read it.

@Gugg I'd better watch it first..!!! What..??? o.O

OMG, Astronomy is going to revive

Hope that it won't die again

@hwlau yep ;-)

I wish the theoretical physics proposal could be revived too somehow, the need for such a site is stronger than ever today ...

@Dilaton Do you need my help to join it?

I hope so, but it need a better strategy to keep it alive

and I guess people are fear for it to die again

@hwlau the theoretical physics proposal?

i mean astronomy

there is no TP proposal right now

Is that you did the retag job for the TP and astro?

@hwlau I am already commited to the restarted astronomy :-)

But I thought one can not yet ask questions, or can I ?

Yeah, I retagged the TP questions and Qmechanic helped if I messed up with something.

Hope that you dont need to do that again :)

Do you have any idea to make TP more sustainable than last time?

@hwlau it was quite fun, I liked looking at these questions, was a good lunch time distraction ;-)

I hung around at TP all the time (silently :-P) and what I observed is that the main problem they had was that there were not enough new questions coming in.

Quenstions got answered after a reasonable time by very nice answers, so there were enough good answerers but not enough askers. The lack of new questions was the reason for low traffic I guess etc ...

So what one should do in my opinion whe trying to restart a TP site is to lower the bar to ask a little bit, such that graduate students can ask too maybe, and then it could probably work. I

@Dilaton I go there few times, and to be honest, I dont understand most of them at that time...

So I do not think that I can give a good judge of whether those are good questions and answers

I think you are right, as most graduate student cant answer those questions , except some postdoc and professors.

So it is a bit hard to sustain

@Dilaton Do you think it is a good time to restart a TP proposal?

@hwlau after a long meta discussions with Moshe who was a moderator, I finally managed to bring up a question, which was not immediately closed and ended with a positive score and nice answers :-P.

@Dilaton It is sad that you need to a discussion whether you can ask a questions.

@hwlau nah, maybe I was just too coward ;-)

I recently asked Robert Cartaino if a new proposal to restart a closed in Beta site would immetiately get closed as a duplicate, but his answer was not conclusive enough for me ... discuss.area51.stackexchange.com/questions/5798/…

And I was discussion with a nice guy if the old proposal could be reopend, but for this one would need some friendly people who have more than 2k rep at Area51, which is quite hard ... :-/

But I feel that a theoretical physics site in addition to Physics SE is very much needed, with as I said the bar to ask a little bit lowered. But I do not dare to write a corresponding proposal at Area51 :-/

I think their policy is quite clear. You cannot reopen an old one, but you can proposed a new one.

Otherwise, why Astronomu and Economic can be proposed again?

Writing a proposal is not a problem, but how can you attract enough people to join it is a a much larger problem.

I certain they wont close it

@hwlau yes, Lumo has reserve a thread for people who want to discuss starting a new theoretical physics site inside or outside the SE network here.

But until now there is not yet much happening there...

But I know quite some people I have talke to who said they would be interested in a new theoretical physics site, I could ping them.

@Dilaton I am sure you can get 200 people interested in TP only from those in Physics.SE, but how can we make it more sustainable

I means how to encourage people ask and answer questions, and come back often

And how can you attract new people. It is important as some people might leave or stop visiting for a while

just like me, I often stop visiting P.SE for a while, but come back later. And glad that it is still exist :)

@hwlau that happens ;-)

I think setting the scope of the proposel similar to the definition of the research-level tag could work. It would mean that reasonable advanced students and people who have gained the knowledge from anywhere to ask reasonably high-level questions could ask too, and maybe even answer some questions ...

Another problem would be the promotion of the proposal, I quess people would not like it to be done on meta. Or wait, was there not a special post to promote other sites ...?

Ah, now I have found it here

I don't really know how people interpret the research-level, but in my mind, it is related to new research area that is not written in any grad textbook. The question is somehow open and still under research that might be put into textbook few decades later. That is a graduate students can normally answer it except that are working on it.

@Dilaton It somehow sounds to me that there is some disjoint in the community.

If the people do not have small overlapping background on some questions, than it seems the community will be disjoint

@hwlau I understand what you mean, but from what I saw that was not the proplem with the former TP.SE, the questions were not that spezialized such that only people directly involved in a very narrow issue could understand and answer them. There were many more general high-level, sometimes not yet completely resolved questions, of interest to many theoretical physicists.

And the questions did not have to be still open by all means.

@Dilaton Do you think that we can have an estimate of how many questions currently in the Physics.SE that will fit into the future TP.SE

Particular, the questions/day. That would be a very good persuasive argument for the sustainability

@hwlau I would say certainly the 408 questions that currently have the research-level tag, and browsing the theoretical physics tags we have there could probably be found even more.

I am not sure if the number of incoming candidate questions on Physics SE today are a good measure to estimate how many there would be on a future new TP site.

@Dilaton I know that, but it is the last year statistics.

I know that nobody likes to here this and many people dont (want to) believe me, but fact is that quite some high level contributers have left Physics SE and/or are passively observing what is happening here, because they think there is no point in posting their high level questions here since they dont get the answers they need. And I have often observed that very high level questions get upvoted somehow but have found no answer, not even by the means of a bounty ...

It is reasonable to assume a fixed fraction of those questions will appear in TP. I would say that the measure is good if we measure how the relative grow of those question here.

@hwlau I am not so good in extracting statistics as Manishearth ... :-/. But I got the impression that the number of such questions is more or less strongly decreasing since the beginning of the year, you know because of what events ... But I dont interpret this as a sign that there is no need for a TP site, on the contrary a new TP site is needed where people interested in higher level questions and their contributions feel more at home and are better appreciated than here on Physics SE.

The few still incoming such questions get quickly flooded down from the first page by more basic and popular questions, homework etc, that are in addition more loved by the majority of the present community.

@Dilaton I heard what happend last year. It is like a chicken and egg problem. But the active researchers tends to have less time for discussion. They just come and go. We need a core group of people than constant keep visiting website (daily) and make contributions. I think 90% of visitor of professors wont do this

I am quite shocke by the large number of basic one line questions and answers that come in and get upvoted.

@Dilaton Yup, but we cannot take the same route as TCS and Mathoverflow. They starts with high level website. Then people demand for low level one. We need to do it in reverse.

Probably you should downvote those question...

@hwlau hm I think the site should not only consist of professors, I observe some good theoretical physics students asking nice technical questions, and maybe the level should be set that they are included too. I all contributions that would not be boring to researchers in nearby fields would be good for a new TP site.

@hwlau I often downvote and closevote such really bad, lazy one line or two line stuff ... But sometimes the appropriate close reason is missing, and people are then saying what is wrong with that question, it is well formulated etc ...

There are so many bad incoming questions sometimes, that I often use all the time I have for down and close voting them, and then I have no time left for reading the interesting and nice ones I like

@Dilaton I think the scope is good. I heard that in the old TP.SE, grad levels questions were moved to P.SE often...

Do you have any idea how to starting and discussing a new proposal?

@hwlau yep, I think (good) grad level questions should be included this time, and I guess many profs are happy to answer good not too basic questions of advanced students too...

I have not yet started any Area51 proposal myself, I would need to have a closer look at how others have done it. Dimension10 recently started a popular-science proposal, so I think one basically writes a description about the intention, scope, targetted audience and such, and the asks example questions. Each proposal seems to have some kind of a meta part too, where additional things can be clarified and discussed.

BTW next week is still my holidays ... :-)

@Dilaton We can just take the TP.SE as template, and put our unanswered research-level there as definition :)

The popular science sounds bad as it only includes physics.

BTW are those two dimension10 related?

@hwlau :-) yep, and slightly adapt the targetted audience.

@hwlau in the popular-science discussion part it was then said, that all sciences should be included, but I dont really know how to ask popular biology or chemistry question ... ;-)

@hwlau the by S-duality related dimension10s worry me a bit too, maybe I should warn him to be careful, a thinkd one of them should unfollow the popular-science proposal ...

@Dilaton Do you know what is the webpage to start a new proposal?