Cap'n Refsmmat

It seems like L'Hopital's Rule would suffice to solve this problem. Have you tried that?

No. If they did, momentum wouldn't be conserved. The total momentum vector would point east before and west afterwards.

You can have collisions where one object is stationary. You can always switch to the perspective of one of the colliding objects, because from its own perspective, it's stationary. That's the definition of an elastic collision. It wouldn't be elastic otherwise. No. One of the objects can give its energy to the other. For example, imagine shooting a pool ball into a stationary ball. The collision could be perfectly elastic, meaning the stationary ball ends up moving away with some speed and the cue ball slows down or stops. Newton's cradle also works with elastic collisions.

Oh. Fudge. They've changed the way BBCodes work so custom BBCodes, like our LaTeX BBCode, won't work with noparse. Everything else will work. Time to file an annoyed bug report. Bug report here: http://community.invisionpower.com/resources/bugs.html/_/ip-board/prevent-other-codes-parsing-does-not-work-r41449

That's interesting, but I don't know French. What makes it impossible to translate?

test Works for me. Old posts will be broken until they're edited and the BBCode is re-parsed.

During class days I block myself from Facebook, YouTube, SFN, and all my other favorite time-wasting sites (something like ten in total) with LeechBlock. Since so much of my homework is done on a computer, I have an almost instinctive reaction when I don't know how to answer a question: switch to Firefox, open a new tab, and start reading something else. LeechBlock embarrasses me with how often I find myself opening a tab with the little "Site Blocked" message. I've only just started this, so I'm not sure how effective it is. I think I've been forced to find other ways of wasting time. I'm working on kicking the habits before grad school starts. edit: as for research motivation, panicked articles like this one are helpful -- at least I know I can get funding! Also, "3,000 curies of Cesium" is a frighteningly large radioactive source.

The answer is "electrodynamics would fail." If you derive Maxwell's equations for electromagnetism, you find that the speed of light is a constant in any reference frame. Remove this restriction and I don't know how you'd solve the equations to get consistent predictions between reference frames. Chapter 12 of Griffiths's Introduction to Electrodynamics is a good primer here.

Well fudge, it's fallen over again. Not sure what's wrong with it.

Think I got it going again. Looks like part of the mail server crashed and started refusing to accept emails, so nothing was getting sent. I fired it up again and everything seems happy. Let me know if it craps out again.

I'll check on it when I get home tonight. Perhaps the server is constipated.

How long has it been since you got a notification?

Why don't you just make a website for it and link us to it?

What do you mean "incorporate it in the website"? Have it learn from posts and reply to them?

Unfortunately IPB stores posts as HTML now, so turning off WYSIWYG won't save you. The editor can still mangle your post in conversion.

A rocket big enough to get into orbit will be noticed by US government surveillance satellites designed to detect nuclear missile launches, and may get you into a bit of trouble. At the very least you need clearance to launch from the FAA.

A GPS receiver capable of functioning above 11 miles altitude and 1000 knots velocity is classified as a munition by the US Government and requires all sorts of paperwork to export or use. You have to find a GPS unit from another country without export restrictions. As for getting something into orbit -- a more modest option would be to create a CubeSat which piggybacks on another satellite launch. Many universities and amateur groups have built CubeSats.

Do it exactly the same way you'd do it with numbers, except with variables instead. Your answer will be matrices in terms of L and M. If you run into a problem doing this, let us know what you tried and where you got stuck.

I believe one of the several paste buttons in the editor toolbar is supposed to paste text without the formatting. D H is right, and I find this very frustrating.

So the numbers you quoted suggest that chondrite is weaker than concrete. How does this lead you to conclude it shouldn't have broken up on its own?

Any electromagnetism textbook will do. Or, for instance: http://farside.ph.utexas.edu/teaching/315/Waves/node37.htm

Dr. Krauss, You often talk about science education, or the lack thereof exhibited by many of our leaders. You've probably heard about the many new companies trying to advance education through the Internet, like Coursera and Udacity. What future do you see for science education in America? Do we have any hope?

Those of you looking for question inspiration can also read the Q&A Dr. Krauss held on Reddit a year ago after his most recent book was published: http://www.reddit.com/r/IAmA/comments/oe96e/i_am_lawrence_krauss_director_of_the_origins/

In the United States, involuntary treatment or hospitalization already requires a court order for any more than a short detention. Rennie v. Klein established the right of involuntarily-committed patients to refuse medication. Now, I suppose if you were under 18 at the time of involuntary hospitalization, then your parents would have the right to make such decisions for you. But adults already have the rights you demand.