Science Thread - General - Facepunch Forum

Why is the pendulum equation ([I]a[/I] = -sin<angle>*l/g) impossible to solve? I asked a friend but he was unable to give a decent explanation.

[QUOTE=JgcxCub;33301628]Why is the pendulum equation ([I]a[/I] = -sin<angle>*l/g) impossible to solve? I asked a friend but he was unable to give a decent explanation.[/QUOTE] Solve? Solve for what?

[QUOTE=Block;33302018]Solve? Solve for what?[/QUOTE] As in, try to integrate that. I'm attempting to find the expression for angular velocity.

Does the military have any actual science/engineering roles for its members? Or do they just hire non-military people to work for the military?

ok this is just sad we had a pop quiz in physics today, and it was really nothing new, nothing hard and I was the only person to get the question right literally everyone but me failed what the fuck [editline]22nd November 2011[/editline] maybe the teacher is doing something wrong, but why the hell am I still doing well in that class while everyone around me is failing?

I didn't do any homework up until the test I had friday, and apparently I got a 94% on it. Which isn't good. I was hoping for a 105% to bring me up to a stable A (~92 or 93%), but instead it only brought me up to an 86%. This means I need to do... HOMEWORK OH GOD

animal physiology exam in two days so much rote learning!

[QUOTE=Contag;33378806]animal physiology exam in two days so much rote learning![/QUOTE] Fucking hate ROTE learning. I probably ballsed up my chem exam this year because I was unable to memorise like 50 different reaction pathways. [editline]22nd November 2011[/editline] I've been thinking lately... the longer we put off venturing into the universe, the longer we take in seriously trying to establish an off-world presence... the more unlikely it gets that we ever will. We're dooming ourselves here. Politicians keep putting these projects off because it's unpopular with the general public due to economic problems. Politicians would rather have 4, perhaps 8 years of guaranteed power than see the continued existence of the human race. We're told, "we'll do it next decade when we're not in debt!" but the longer we leave things, the more resources we as a species use, and the more resources we use the more expensive they become (due to their increased rarity). By putting off a serious space colonisation effort we're shunting it down the line to a time when we really DO need to leave Earth due to an impending disaster or a lack of resources to sustain us as a species - and when this time inevitably comes, when it finally becomes imperative that we leave Earth to survive as a species... it's going to be inobtainably expensive. I only hope that when that time comes we as a species can cast aside the notion of money and wealth and work together as one to achieve a common, absolutely necessary goal. ... I only hope we can manage that.

[QUOTE=Collin665;33377334]Does the military have any actual science/engineering roles for its members? Or do they just hire non-military people to work for the military?[/QUOTE] Depends what you mean. Both of my brothers are in the Air Force. Neither of them had any real skill with what they're job is back in the civilian world. One of them does avionics and the other does water/fuel management (plumbing, basically). Both required a few weeks of hands on technical training. I know my bro that does the Avionics had to learn basic electrical engineering. I think if they stay in their job long enough they're eligible for an Associates of Science degree, just off their work alone.

So I started reading about the Tokamak, and I was wondering. Isn't it basically "creating" the same sort of power as the sun runs on?

Yeah, it's a fusion reactor. It works, but it isn't efficient. For the reaction to be possible, it must be heated to enormous degrees (and you must subsequently cool everything else). This currently requires much more energy than it will produce itself. [url]http://en.wikipedia.org/wiki/Tokamak#Plasma_heating[/url]

The only science I know is Intertia is a property of matter Also I came here accidentally

Sigh, time to get the books for next semester. Our physics book alone is $152...

Why are education books so god damn expensive?

Because they know they can charge as much as they want and get away with it. Plus they're somewhat expensive even in manufacturing, but they do get overpriced. Some companies have not-for-profit textbooks that are much cheaper, but obviously most courses don't use 'em...

i was quite lucky with my course - they'd been very selective about the textbookx. i was required to buy 3 textbooks (inorganic, organic and physical chemistry), which were around £25-30 each and that was it for the whole 3 year course - i picked up a couple of other oxford primers which are quite small books that are around £10 each but nothing like the spending on some of the other courses.

anyone have ideas for steps that deal with circular motion and simple harmonic motions for a rube goldberg machine for my physic's semester exam? i can't come up with anything mostly on simple harmonic motion.

[QUOTE=mike;33640672]i was quite lucky with my course - they'd been very selective about the textbookx. i was required to buy 3 textbooks (inorganic, organic and physical chemistry), which were around £25-30 each and that was it for the whole 3 year course - i picked up a couple of other oxford primers which are quite small books that are around £10 each but nothing like the spending on some of the other courses.[/QUOTE] I got super lucky : one textbook, and they gave it to us free. :v: [editline]10th December 2011[/editline] Also, having had the concepts of proper time and length introduced in special relativity, I now understand things A LOT BETTER. This stuff really is excellent fun.

So I'm trying to construct this playable analogue synthesizer. But I'm stumped at how I'm supposed to design the controller. [img]http://filesmelt.com/dl/osc1special.gif[/img] Now this here is a sawtooth oscillator I've built. Its frequency is dependent on the value of the capacitor. So let's say that I want to be able to play 3 different tones. So I calculate and simulate values for three different capacitors - C1, C2, and C3. But the problem is how I'm supposed to trigger the switch via for example sending a dc voltage by using a keyboard. At this point I'm thinking that it just might be easier to build one oscillator for each tone. That way it wouldn't have to be polyphonic either! :P Basically - how do I control a switch / change a circuit just by using DC voltage (preferably without logic gates)? There should be one DC input for each tone/capacitor.

I might be way off, but don't you need a transistor? Plug a base voltage into one end and your DC control line into the middle. Current goes trough based on the DC line being high or low. (sorry if this is complete gibberish. It's been a while since I've worked with electronics)

Ahh very clever, I will look into that!

Fuck I'm so nervous about this mechanics exam. I'm awful at mechanics.

Is it inevitable that professors are always going to make jokes about the Poynting vector? [editline]12th December 2011[/editline] [QUOTE=JohnnyMo1;33687702]Fuck I'm so nervous about this mechanics exam. I'm awful at mechanics.[/QUOTE] I didn't get a good nights sleep last night because I was so anxious about my EM final today, which turned out fine.

Wasn't as horrendous as it might have been. I feel totally confident about one problem, mostly confident about another, okay about the third and ugh fuck about the fourth.

Are my posts in this ([url]http://www.facepunch.com/threads/1147502[/url]) thread scientifically correct, I'm basing it off the principle that you can't really detect photons without changing them.

quick question, if you have two waveforms that are identical but where one is the negative displacement image of the other (i.e. flipped both in the y and x axes), will they always cancel out if they're travelling toward each other and they meet?

Yes, at least momentarily.

I don't think so. If you have sin (x + 5) / (x + 5), for example the limit to infinity in the original one is in x = - 5 and in the inverted one, it's in x = 5

Thanks to the principle of superposition. [editline]13th December 2011[/editline] Are we not talking about continuous waveforms here? [editline]13th December 2011[/editline] This is a science question, not math, so I assume it has to be physically possible.

Yeah, I'm talking about waves-on-a-string type question here. [editline]13th December 2011[/editline] Basically, I need to draw a bunch of snapshot diagrams for two waves travelling in opposite directions. Is it an acceptable method to draw the two waves as if they were completely unaffected by each other (e.g. on separate strings), and then just add vector displacements? It just seems weird to me that such waveforms can simply pass through each other like that.