blackhole123

I was discussing the future of cars and breaking out dependence on oil with a friend, and fuel cells came up. I thought that fuel cells would be a major breakthrough because they are more efficient than combustion engines, and hydrogen is a lot easier to get than fossil fuels. He claimed that fuel cells would not increase efficiency because you would still need electricity to power the car, to carry out the reaction of the hydrogen that would give energy. I'm sure he is mistaken, or else fuel cells would be worse than a straight up electric car, but I was shaky on my understanding of fuel cells so I couldn't successfully rebut him. I believe I am correct that fuel cells produce electricity with a chemical reaction. How is the electrochemical reaction started, does it take energy? And how costly is hydrogen production? What should I say the next time he claims that fuel cells won't work since "you still need electricity to power the car"?

http://www.msnbc.msn.com/id/30810514/ I can't think of ANY car on the market that gets that many MPG right now. Except maybe hybrids. I'm really concerned about the environment and I'm about as liberal as they get, but is this even possible?

I've seen people claiming the oceans will rise 20 feet if Antarctica melts. Why then, with the seasonal melting of half the continent, do sea levels not rise and fall every year by 20 feet? I think the answer has something to do with the ice already being in the water so when it melts the level is still the same, but then what other is global warming melting? I thought so far it is just that less and less ice is refreezing, which would mean that it has not changed sea levels at all yet. How could it change sea levels?

Wow thank you so much, that clears it up so much! I was under the impression it was the shape of the volume, but now that I see it is actually just the method it makes so much more sense. So around the x axis in terms of x it is easiest to use the washer method. And around the y axis in terms of x it is easiest to use the shell method. Sooo.... would it be opposite of that when it is in terms of y? Because most of the time I am given "y=..." I understand I can solve for x, but I'm sure there is an easier way. EDIT: Oh wait, if it is something like y=x^2 it IS in terms of x right? Woops EDIT 2: Wewt, just did started my homework and I GET IT. Checked the answers that I have gotten so far and its actually working. Before I could kind of do it if my hand was held but now I can do it and understand why! Thanks again! Comprehension is a beautiful thing!!!! EDIT 3: Could you explain what they are saying in my book about the different methods being useful for whether the "natural intergral is perpendicular or parallel to the axis of rotation"?

IM SO CONFUSED (and it doesn't help that my teacher barely knows what she is talking about). I don't know when an object that is rotated around either axis is a washer or when it is a shell. If the problem says "do volume by shell" or "do volume by washer" I can get it right. I can't tell on my own though. http://img297.imageshack.us/my.php?image=ahhcalculus.png For example, get that in #1 it is a disk when rotated around the x axis In #2 though, when you rotate that shaded part, formed by the equation x^3 and some other equation that intersects it at the origin and in the first quadrant somewhere, around the x-axis which one is it? What about around the y-axis? I think I was told that around the x axis it is a washer, and around the y it is a shell. WHY? To me a washer is a shape like #3, where it has an actual length before the inside part is missing (shown where I drew the red lines). However, in #2 when you rotated it around the x axis, it looks more like a cone in that from the circular edge when you move in it immediately starts to slope down. How can that be a washer? And how is it different when it is rotated around the y axis? Does it have something to do with dy or dx changing parallel or perpendicular to the axis you are rotating it around? I'm so confused and I've been grappling with this all day now and I don't get it.

I'm going to a state university so its $6900 a year. I got a $2500 scholarship. Now with the new stimulus package, they extended the hope scholarship to include people with income of $160,000 or less and they bumped it up to $2500 for two years. So thats $6900-$5000= $1900 plus a $200 tax credit from NY state= $1700 to go to a great university. Just like that, Obama saved my family $10,000 because my sister is in college too. My family is actually making money off of this because with all my sisters scholarships she only pays $500 a year but she still will get the 2.5k which we can use to pay my $1700. So we gain $300 a year for going to college. There is another state program too that could get me $500 more too. Everyone make sure you take advantage of this. A common misconception is that if you are taking out student loans then you aren't paying for education and won't get the 2.5k, but this is not the case. Everyone can get it.

I took AP chem last year and got a 3 on the exam. I want to go into chemistry as my major but I can already hardly remember anything about the course. I know it seems sad but I think I've forgotten so much. I don't want to be lost next year when I get to college, are there any fairly thorough AP chem review books that I could get my hands on and essentially reteach myself the course? I don't want exam review necessarily just review on the course in general so I can prepare myself. I wish I still had my old textbook, but they are so expensive. Thanks.

Well, I heard if you want to go into research then you pretty much have to have your PhD, and thats what I'm interested in. What type of degree are you getting, BA or BS? I'm also looking at the syllabus for undergrad chemistry, and my junior year I'm going to have to take 5 chemistry courses per semester.... There isn't enough time in the day!!! How is that possible?!

Update: I'm 7 weeks into bio and I really don't like it. I just toured the chemistry department at the university I will be attending and I am definitely decided on chemistry now. Just a couple of questions directed to those who have taken chemistry courses. Be honest, how hard is it? I took AP chem last year and now I have a whole year or forgetting it before I go to college next year. I won't be lost will I? I'm definitely planning on not having a life and spending most of my time with TAs figuring out homework. Because I chose to take AP bio this year I have no experience with physics. I will have to take general physics at some point, how hard will it be for me with no physics background whatsoever? It's kind of daunting to think that 4 1/2 years from now I will be going for my PhD if everything turns out as I plan.

Last year while taking AP chemistry I was all decided that I wanted to be a chemist. Now I'm taking AP biology, and I'm having second thoughts about my choice. I went to a lecture series during the summer where they had biologists talking about things like evolution and their research, and hearing all their stories about studying and collecting specimens in exotic places really got me going. I've always been very interested in both subjects, and I'm just so torn. This mainly stems from a fear that biology may not be a practical field to get a job in. I don't want to a doctor or pharmacist, so I don't know what kind of job a chemistry degree would get. Lets say I go on to get my PhD for one of these, what jobs are available to me? What is the most practical way to combine both of these fields? Biochemistry? Molecular biology?What exactly are these and what do they study/what kind of jobs do they have? Am I limited to some day just getting my PhD and then being a professor at a university somewhere? The problem is, I'm not too interested in things like drug research for chemistry, and I don't want to spend my life in industry like a factory somewhere getting paid a lot but not doing anything meaningful (no offense to anyone with a job like that, it just doesn't appeal to me). So how practical is a degree in biology? I heard its a lot harder to get a job since it is an easier course that is more memorization than smarts. I'd love a way to fuse the two fields and get more complex. I think if I could choose my future I would be a college professor like the one I saw this summer, who spends half the year teaching and the other half doing cool research. Ideally I would like to focus on chemistry but have it be related to biology. Help me! I'm going into college next year!

lolcats? What?

I'm working on my summer assignment for AP bio and I couldn't get a couple questions. Indicate the type of learning illustrated by the following example: Ewes will adopt and nurse a lamb shortly after they give birth, but will butt and reject it if the lamb is introduced a day or two later. The only types of learning I know are classical conditioning, operant conditioning, spatial learning and habituation and none of them fit. How is a female birds fitness associated with her ability to choose a mate by deciding among displays and adornments that "advertise" the health of the male? How does the females fitness have ANYTHING to do with choosing a mate? Unless they don't mean physical fitness? I'm confused on this one. thanks.

For a final project in AP chemistry we have to do a lecture demonstration. Its basically just a lab that relates to at least 3 units we have done this year, a report about it and a demonstration of it to the class. I really don't know what to do. I don't want it to be too simple like just lighting some powder on fire, but I don't want it to be too complicated or dangerous. I've seen some cool ones in videos but most of the time they don't give specific values I would need to do the experiment myself. Like this one which I think would be cool to do: http://exploscience.com/Home/Green%20Fire%20Light.wmv but I couldn't really find any info on it. I also think making ferrofluid would be really cool but it's probably too advanced for me or it wouldn't relate to the stuff we have done. Any ideas/sites that have procedures for cool lecture demos on an AP chem student level? is the "barking dog" experiment dangerous?

http://www.noob.us/miscellaneous/how-to-make-hot-ice/ looks like fun, i need to try this.

Im not a goth though...

I started out playing LOTR, switched to 40k and had a fairly large space marine army. I made a nid army but I never got around to painting a lot of it, I havn't played in a couple years. I play magic now

Some sort of bird.

Obviously we won't be around forever, I wonder what the circumstances will be, a quick death from a catastrophic event? Maybe something that would be considered science fiction today? I wish I could travel into the future and see what society will be like.

that is so cool

This is different than that. They needed more troops to actually take control of Europe, the reason he is sending more troops is because we already took it over and there are extremists in the country.

http://www.cnn.com/2007/POLITICS/01/10/iraq.bush/index.html This kind of reminds me of another war that wasn't solved by sending more troops....Viet...something...

Ok... or someone could tell me whats wrong with Java.

I thought id revive this, anyway heres the new link: http://www.wavelit.com/popup/playerAfricam.asp# Right now there are 3 giraffes!!!

Well, I'm no scientist but I saw him speak in Chautauqua and most of what he said made sense. I can't imagine why someone would deny that global warming exists.

It seems like everyone is experiencing warm weather. Is global warming to blame?