• Physics Discussion
    973 replies, posted
Still good practice. I think you mean Co-60. Great indicator of resolution, since it has two higher energy peaks pretty close together.
Yeah it's cobalt of course. Indeed, it was also pretty damn cool to see a spectrum forming, corresponding 1 to 1 to its decay scheme.
I'm a little bit sad that our nuclear physics labs weren't as enjoyable as they could have been (still were, though - just less so than was possible). Our nuclear physics class was coupled with a 'radiation and optics' class, and to accommodate for the size of the class half of us did nuclear physics labs for the first half of semester, and half of us did optics labs, and then we switched around. Unfortunately we were the first group through the nuclear physics labs and for every 4 hour lab session we had we lost anywhere between an hour and an hour and a half being taught by our lecturer in the lab the stuff that we needed to know for that particular experiment (unlike in/before the optics labs in which you could literally learn what you needed to right then and there in the prac notes in about 5 minutes flat). And then of that remaining time we needed, I think, an hour break (or maybe it was a half hour) for lunch. Of course future lab groups had to have the lunch break too, but they didn't lose the hour or more at the start of the lab because they'd already learned that shit through 6 weeks of lectures. Then to top that off, the equipment (like the NIM bins and their modules) that we were using was completely different between each group during each lab (even though every week everybody did the same experiment), so everybody always encountered issues setting up and running stuff (that weren't easily solved by asking neighbouring groups for help because the equipment they were using was rarely the same or even similar as the equipment you'd be using). We only had our lecturer and ONE other demonstrator to take care of everyone, so you'd frequently be waiting 15-20 minutes for them to come and help you out and solve YOUR specific problems. I don't think there was a single experiment that any of us got 100% completed, however obviously my lecturer (being the awesome guy he is) was understanding of the situation and told us just to do what we could in the given time and that he'd mark us only on that (and make sure that the other demonstrator, who was a bit of a cunt, would do the same).
We were split too but we had to learn at home before the stuff started and had a 15 minute test to see if we got our stuff right and then we had to figure out the rest by ourselves.
Argh. I can't tell if I'm just being slow because my sinuses are blocked to all hell, but I'm trying to derive the position-energy uncertainty principle and I found that the commutator between the two is itself an operator; is this something that can actually happen, or have I cocked up? The only other time I've seen it done in this context is for position-momentum, and that came out neatly as i hbar. [URL="http://i.imgur.com/6jbDX9l.png"]Linked for size[/URL]. (Stick the squared on the two hbars towards the end; I just noticed I lost them in typing the Latex up).
[QUOTE=Killuah;39653560]We were split too but we had to learn at home before the stuff started and had a 15 minute test to see if we got our stuff right and then we had to figure out the rest by ourselves.[/QUOTE] We had an online test to do as well (mostly for health and safety stuff, if I recall correctly), but on top of that we'd be given basically an hour's lecture as well to make sure we were 100% sure on what the fuck was going on.
[QUOTE=Greenandred;39654072]Argh. I can't tell if I'm just being slow because my sinuses are blocked to all hell, but I'm trying to derive the position-energy uncertainty principle and I found that the commutator between the two is itself an operator; is this something that can actually happen, or have I cocked up? The only other time I've seen it done in this context is for position-momentum, and that came out neatly as i hbar. [URL="http://i.imgur.com/6jbDX9l.png"]Linked for size[/URL]. (Stick the squared on the two hbars towards the end; I just noticed I lost them in typing the Latex up).[/QUOTE] I did the calculation on paper and got the same answer. I reckon it must be right, or at least I don't think there's been a mistake in the maths. I'm not sure how to interpret the result either though, it sure is weird/nonphysical. I can't find any information on the position-energy uncertainty principle on google either, if it's even a thing: there's only the position-momentum and energy-time ones I can find anything on. Is it perhaps because you can usually calculate energy if you have the momentum and you know the mass, and vice-versa? Classically, if you know p and m, you can calculate v, and from that you can know what 1/2mv^2 is. [editline]20th February 2013[/editline] hang on a minute... hbar^2/m d/dx is equal to (ihbar/m)*p hat and so the uncertainty sigma(x)^2*sigma(H)^2 is greater than or equal to (hbar/2m)*p hat so I guess that's, uh, more like a reasonable thing?
Think I'm gonna approach the string theorist who taught my GR course and ask if he has any research projects for undergrads. His description of what you'd have to study to have him as a graduate thesis advisor sounds really awesome: quantum field theory, general relativity, differential geometry, and algebraic topology. That is pretty much a list of all my current interests in physics and math.
[QUOTE=JohnnyMo1;39657088]Think I'm gonna approach the string theorist who taught my GR course and ask if he has any research projects for undergrads. His description of what you'd have to study to have him as a graduate thesis advisor sounds really awesome: quantum field theory, general relativity, differential geometry, and algebraic topology. That is pretty much a list of all my current interests in physics and math.[/QUOTE] Those're pretty fascinating areas :) I'm looking at going into string theory next year. Sounds fun!
Went to see CMS and even got to see the underground parts. Didn't go to the service tunnel cause they were still going to run tests though.
the only errors ive been getting for pretty much an entire month's work of physics practice questions have been dumb mistakes like not reading the question carefully or not seeing that it was kilo-units or whatever ive been getting all the concepts right on my first try, im pretty pumped for this midterm
ew units lol
I've reached the maximum amount of points for my homework, but there's one last interesting question: "Consider the application of Lagrange multipliers to the question of the death of Gwen Stacy in the Spiderman comic books. Is it applicable, and why, or why not? Solve the question of why she died. Take her body mass to be 50 kg, the length of the webbing to be 100 m and make any reasonable assumptions needed."
Green Goblin throws her off the Brooklyn Bridge, Spiderman shoots his webbing at her in an effort to catch and save her, but she dies, supposedly from the whiplash. [editline]20th February 2013[/editline] [URL]http://en.wikipedia.org/wiki/The_Night_Gwen_Stacy_Died[/URL]
Can someone totally explain to me why it says delta-H is half lambda? ( Regarding light interference in an air wedge) [IMG]https://dl.dropbox.com/u/888382/whatthepotatoesface.jpg[/IMG] Wouldn't delta-H only be one lambda? Oh god i'm confusing my brain so much. the PD between A and B would be integral, but I just don't see how that makes delta H half lambda.. For A and B to be adjacent points of maxima, wouldn't the path difference between them be Lambda? If so, shouldn't delta H be lambda then?
It's not distance between maxima - it's distance between a maxima and a minima, with 0 in between. A wave goes +0-0+0-0+0-. One lambda is +0-0, which is two bright stripes and two dark stripes.
[QUOTE=Goodthief;39607846]Can anyone here explain to me how the equation for the displacement of a particle undergoing simple harmonic motion is x=x0cos(wt) where, x0=the amplitude of the cos curve and w = omega I just don't understand how someone once looked at the path of an oscillating ball on a graph and wrote down the equation x=x0cos(wt)[/QUOTE] I found this and remembered your post. [media]http://www.youtube.com/watch?v=SZ541Luq4nE&list=PLF589671C6A7C0731[/media]
[QUOTE=Falubii;39675532]I found this and remembered your post. [media]http://www.youtube.com/watch?v=SZ541Luq4nE&list=PLF589671C6A7C0731[/media][/QUOTE] wow thanks, this is practically everything I need to know for the entire simple harmonic motion chapter. The explanation on why the graph of the potential and kinetic energy of an oscillating ball are like that is very useful.
[QUOTE=Nikita;39674069]It's not distance between maxima - it's distance between a maxima and a minima, with 0 in between. A wave goes +0-0+0-0+0-. One lambda is +0-0, which is two bright stripes and two dark stripes.[/QUOTE] If it was half lambda, wouldn't it be entirely destructive interference though? A crest meeting a trough , and trough meeting a crest would completely negate it, wouldn't it?
[QUOTE=JohnnyMo1;39662349]ew units lol[/QUOTE] That great feeling when c, hbar and the magnetic and electric constants all disappear <3
To any astronomy physics students, could you please tell me why brown dwarfs fail to become stars? Basically information on Stellar's Evolution
If you're interested in particle physics and ever get a chance to visit CERN, do it. Hostel was meh, food was expensive, but otherwise it was pretty interesting and I'd definitely go there again.
I just found out that every episode of The Mechanical Universe is online. :D
I can't find the Mathematics thread and this can be applied to physics in any case so I guess I'll ask here. I have a second order autonomous system : dx/dt = f1(x,y) = 2xy , dy/dt = f2(x,y) = x^2 + y^2. I have been asked to find the nullclines and give a qualitative sketch of the phase diagram. I understand that nullclines are when f1(x,y) and f2(x,y) are equal to 0 - in this case the x-nullcline is the x axis and y axis , the y-nullcline is simply the point (0,0). This implies that the fixed points of the system is just the point (0,0) (intersection of nullclines). What I don't understand know is how I go about drawing the phase diagram. Anyone here know what I should be doing? Cheers. Edit: found the maths chat, will post there as well, thread order on GD is all over the place.
[QUOTE=Deathhunter;39688450]To any astronomy physics students, could you please tell me why brown dwarfs fail to become stars? Basically information on Stellar's Evolution[/QUOTE] Sure. They're not massive enough to start core fusion. Their heat generation is from friction in the collapse, but eventually they'll just radiate all their energy and just sit there as a small cloud of gas.
If you got like a tennis ball sized lump of neutron star, and dropped it(assuming you are the hulk) would it just plow stright through to the core of the earth?
[QUOTE=Hattiwatti;39688832]If you're interested in particle physics and ever get a chance to visit CERN, do it. Hostel was meh, food was expensive, but otherwise it was pretty interesting and I'd definitely go there again.[/QUOTE] My school's been trying to pull off a trip to CERN for the past 3 years. Each time it failed to gain enough interest. This year, they managed to pull it off, and got enough pupils in the lower 6th who want to do it to make it feasible. Sure they extended the invitation to the upper 6th, but it's basically right before the full A level exams, so it'd be insanely stupid to go. Not to mention the cost, man they're charging a lot. Got to see the Diamond Light Source a couple of years ago though, so it's not all bad.
[QUOTE=alien_guy;39690942]If you got like a tennis ball sized lump of neutron star, and dropped it(assuming you are the hulk) would it just plow stright through to the core of the earth?[/QUOTE] It would oscillate back and forth making our planet into swiss cheese.
[QUOTE=Terminutter;39691152]My school's been trying to pull off a trip to CERN for the past 3 years. Each time it failed to gain enough interest. This year, they managed to pull it off, and got enough pupils in the lower 6th who want to do it to make it feasible. Sure they extended the invitation to the upper 6th, but it's basically right before the full A level exams, so it'd be insanely stupid to go. Not to mention the cost, man they're charging a lot. Got to see the Diamond Light Source a couple of years ago though, so it's not all bad.[/QUOTE] Man, our high school goes to CERN every year :v:
[QUOTE=booster;39693605]Man, our high school goes to CERN every year :v:[/QUOTE] For us it's every second year, so everyone gets a chance to apply for it.
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