April 14: here are a few examples of very nice concept maps, in random order: example 1; example 2; example 3; example 4. About 15 of you received bonus points for doing a very nice job of this, and of those I selected 7 examples to scan (mostly because they seemed either more complete, or more artistic, but it was close), but then several scans are un-readable so only these 4 survived. I hope this was a helpful exercise in getting you to think about the material, and that these maps will help everybody else study. You can pick up your last hmw anytime during office hours (and sorry for the delay).

April 12: Mistake corrected in problem 2, hmw3 (thanks, Nick).

Re: the "research" problem in hmw3: by "research", I meant you trying to find, on your own, a possible solution to that problem. Obviously, things would need to be simplified significantly for this to be possible, and I was hoping you'll be able to come up with a possible such case. It seems that most of you understood "research" to mean googling this problem and seeing what other people have done. That is a form of research, of course, but I'd much rather prefer that you spend some time trying to come with your own solution (even if you're not successful) rather than just seeing what others have done and spending time copying that down.

For those who did google things up, congratulations to those of you who referenced where you took the work from. In some cases, it seemed quite likely that the solution was obtained by such means (otherwise how would you know that this was Euler's problem?) but there was no reference available. This is not a big issue in the context of this homework, but generally you must give credit where credit is due -- as scientists, it is wholly unacceptable to pass somebody else's work as yours. If you get caught doing that, This can get you into BIG trouble, so you should get used to referencing anything that is not your own work.

In the end, I gave some extra credit to 4 of you, who seemed to have derived your own solutions. I post two of these here (the other two were quite similar) -- both use symmetries of the masses and initial conditions to simplify the problem so that it is fully solvable in the end (without any further approximations). Solution 1; Solution 2 page 1, page 2, page 3.

Problem sets from 2010

Problem set	Due, in class	Solutions
Problem set #1	Wed, Jan. 20	Set #1
Problem set #2	Mon, Feb. 1	Set #2
Problem set #3	Wed, March 3	Set #3
Problem set #4	Wed, March 17	Set #4
Problem set #5	Wed, Mar. 31	Set #5
Problem set #6	Wed, Apr. 14	Set #6