# sfpublic

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29

1. ## difference between congruence and equality

what is the difference between the following statements: a congruent (triple equal sign) to b mod (n) and a=b mod(n)?? do they differ in any properties ?
2. ## number of layers in a surface of a substrate

in inorganic chemistry when we define a surface, how many molecular layers/ or 'depth' are we talking about.
3. ## number of layers in a surface of a substrate

in chemistry when we define a surface, how many molecular layers/ or 'depth' are we talking about.
4. ## totient function

can you please take a general case and solve it mathmematically..im not able to get the statement how did you arrive at the statement that the sum of totients is n?
5. ## totient function

how is summation of all phi(d) = n where d|n? thanks

7. ## Imortality Drive

Check Out William Cooper's "Behold A Pale Horse" Page#397 http://bit.ly/NyDe8
8. ## Synthesis Problem

Hi, I just had a test question for a synthesis problem (you have methoxybenzene and you want 1-methoxy-4-propylbenzene) and it was considered completely wrong, I was wondering why: Methoxybenzene ---> (1) + FeBr3, Br2 (2) + Mg, ether (3) +1-bromopropane, ether --> 1-methoxy-4-propylbenzene The right answer is (1) + AlCl3, 1-chloro-1-oxopropane (2) H20 (3) Zn(Hg), aq HCl. I understand why the right answer is right, but I don't understand how my answer is completely wrong, and I got zero points for it. Merged post follows: Consecutive posts mergedanyone? any help would be great, thanks!
9. ## NanoPutians

Anyone see this article yet? Synthesis of Anthropomorphic Molecules: The NanoPutians Stephanie H. Chanteau and James M. Tour

thanks
11. ## upward force at terminal velocity

a is 0, but i assume there must be some upwards force. no?
12. ## upward force at terminal velocity

I know the forces of gravity and drag must be equal, but I don't know how to calculate them given only that info.
13. ## upward force at terminal velocity

A 50 kg box falls at its terminal velocity of 70 m/s. At this point, what is the upward drag force, in newtons?
14. ## solar and wind energy

I want to learn more about the sciences of PV and thinfilm solar panels, can anyone point me in the direction of a good book on the subject (or webiste)? Such as how they are made and how they actually harness energy. Also, if anyone knows where to read more about wind energy, it would be greatly appreciated.
15. ## making sulfuric acid

You people are such pessimistic losers, you call yourselves senior chemists? Yet you spend so much time attacking a curious 13-year-old who wants to make H2S04, pfftt... If you were a true chemist you would never even think about trying to tell somebody something is impossible, you would extract joy from telling people how to do things, no matter how dangerous, the only reason i can think of in terms of you people telling someone not to try and make sulfuric acid is because you yourselves once tried to make up a batch but failed miserably, now in your worthless freetime you spend your fatass days sitting on a computer typing away insults at people who want to try and accomplish something that you failed at. You make me sick. And for the record, making sulfuric acid is not that difficult at all, you simply need hydrogen peroxide, and an appropriate setup where you can pump Sulfur Dioxide gas into the liquid, and you will get sulfuric acid, the purity obtained depends on the purity of the Peroxide, but if you have a low purity peroxide then you can increase the purity in many ways, my favorite way is by sparging. Sulfuric acid was first synthesized in around 800ad i think, by a Persian chemist, if you morons can't emulate a 1200 year old procedure in your own modern living-enviroment then i wouldn't even consider your chemical-knowledge to be on par with a first grader. Stupid old men. But i forgot, if anybody tries the experiments that you so miserably failed at all your life they will blow there eye out or cause themselves immense damage, because they too are retards like yourselves, right? You just continue sitting there living your fatass-days away by believing that your something, spitting out words that are designed to try and make you look like you are actually something, something other than the nothing that you are and always will be, unlike people who aren't afraid to try, and put there life at risk in the process. Furthermore, for the record, i have not tried this, but if you look at the MSDS for Sodium Bisulphate you will see that according to it when Sodium Bisulphate is dissolved in Ethanol it disintegrates into free Sulfuric acid and Sodium Sulfate.
16. ## Ferrofluid display

(Distilled) water works with Ferrotec (Ferrosound EFH1) to some extent, but vodka* works better and does not mix with the water at all, although a small amount of carrier will separate from the ferrofluid and float. Like the original poster, this is an oil based ferrofluid and therefore attracted to plastic. A smooth glass cell works quite well, but some small droplets of ferrofluid are likely to stick to the odd imperfection regardless. Just be sure to pre-wet (i.e; fill) the vessel with your filler fluid before adding the ferrofluid. A stoppered bottle with seal is best, as trapped air can complicate things. *Essentially pure ethanol-water mixture, my best guess from the MSDS for an existing commercial cell, of which there are three suppliers
17. ## decrease Radius of penny

hello guys im doing a science experiement for a IB physics class where i have to simulate a penny dropping from a empire state building we have a paintball gun we are using to shoot the penny 65mph (terminal velocity) so my problem is that the penny doesnt fit into the guns barrel IT ALMOST FITS like 2mm difference in size, anyone have any ideas on how to decrease the diameter of the penny enough for it to fit into the barrel? im open to all ideas
18. ## Hydrogen Molecules

Where might I be able to find a list of molecules that have hydrogen in them. Such as water, amonia, etc. I know there are way too many to name, but where could I find such an answer?
19. ## Bubble Dome

say this works and you did this... how would you get in and out of your new fields? where would air for inside come from? why wouldnt the inside be water also? 2 of my questions>
20. ## Dark Matter/Sonoluminescence...

While reading the article "Can this experiment identify dark matter?" on Physorg, [link]http://www.physorg.com/news112281907.html[/link] I began to think of a similar experiment, however a little different. But would the science of Sonoluminescence and the experiment "http://www.techmind.org/sl/" have anything in common. Since the orgin of the bubbles found in the Sonoluminescence experiment have yet to be explained, is it possible that the bubbles/energy bursts that are created are resulting from dark matter interactions? Please ignore if you dont care. This is a random thought/theory that has no backing whatsoever.
21. ## Random equation curiosity

hi, I am using the equation E=h^2/pv E=Energy h=Planck const p=momentum v=velocity How might I test to see if this is correct?
22. ## Vocabulary: Unability to scale difference

Difference as in change (of surface). Unability to be measured due to an explicit nature as if beyond us. If it helps, don't think physics or relativity, think life. I think the problem is, when I asked what it is[/b], you're thinking of and effect or something in-process inward or outward. Instead of a word, that describes just an inability to be measured.
23. ## Vocabulary: Unability to scale difference

Imagine a big ball. It's made of a glass-like substance. Now, you aren't able to measure the scale of difference. What is the UNABILITY of the property to be measured to a scale of difference to? What is the keyword?
24. ## Vocabulary: Unability to scale difference

What's the scientific word for this? Like... not comparable in a sense.
25. ## a REAL SuperHero!

I currently have to do a project for grade 12 science were I have to create A person who can generate lightning. I have been reading alot about lightning but i need to way to explain how it could be generated on comand by a human. I is aloud to be far fettched as long as it envoles some science. I have also been reading about doornob shocks wich i thought could be used as a suttle version of it. if anyone has any ideas or links for me to read that would be reat Thank You PS hope this is in the right section
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