# Kedas

Senior Members

695

1. ## Help! Moment of inertia??

Not sure why you talk about 2D formula's, there are none for MOI. You know very well that it is not possible to have a mass without a volume. Maybe on some quantum level but I'm sure these formulas don't apply there. Even if the height is only dh it would still be a cylinder. And simplifying the formula for certain applications is ok for me but that still doesn't mean that a circle has a MOI. Unless you like to change the definition of a circle that it has a height. What you are saying is as interesting as saying that a circle (r>0,L=0) does or doesn't have an electrical resistance. if there is no distance to travel there no meaning in the word electrical resistance.
2. ## Help! Moment of inertia??

From what I read genralz isn't interested in math for the math. The simple fact is that the MOI formula requires a mass to have some meaning. Yes you can make up an mass that has no meaning, I don't care. genralz, in case you mean MOI of a cylinder or cubiod etc. here are the formula's. http://en.wikipedia.org/wiki/List_of_moments_of_inertia
3. ## Help! Moment of inertia??

A square or circle doesn't have a volume/mass therefore it has no moment of inertia. used if you want to know how much energy is in there. You mean http://en.wikipedia.org/wiki/List_of_area_moments_of_inertia "The second moment of area, also known as the area moment of inertia or second moment of inertia " used if you want to know how easy it will bend and where.
4. ## Physicists resolve a paradox of quantum theory

I didn't find the news forum to post it in. Anyway, I was wondering if this is related to the Heisenberg's Uncertainty Principle or am I understanding it wrongly?
5. ## Physicists resolve a paradox of quantum theory

http://www.physorg.com/news151164690.html
6. ## Spooky wave interference

http://www.physorg.com/news141394051.html
7. ## Chance to see a major asteroid impact. On Mars.

no impact: http://neo.jpl.nasa.gov/news/news156.html They must have used their gravity beam ;-)
8. ## Chance to see a major asteroid impact. On Mars.

If they don't know yet if it will impact mars then a close fly by could change the orbit of it so it is on track to make a collision with an other object, maybe earth in 2011.
9. ## Chance calculation

Thanks uncool. My weird 'feeling' example feels much more right now
10. ## Chance calculation

Thanks for the explanation 1-((n-1)!/n!) looks more right because it doesn't look too simple
11. ## Chance calculation

It looks right for n=2 and n=3 but n=1 should be 1. and if n is very large than the change that at least one stays at its current position is very high. So if I have a cube of water and give it a good (random) shake. Then I can say it is very likely that at least one molecule arrived on it's previous position. That sounds a bit weird?
12. ## Chance calculation

If you have an ordered list of numbers and you randomly change them what is the chance that at least one number will stay on its previous position? Or more practically if you give everyone a number and you let them blindly pick a number. What is the chance that at least one persons picks his/her own number again.
13. ## Evolution more predefined than we think

Evolution is deterministic, not random, biologists conclude from multi-species study A multi-national team of biologists has concluded that developmental evolution is deterministic and orderly, rather than random, based on a study of different species of roundworms. The findings are reported in the latest issue of the journal Current Biology. http://www.physorg.com/news114700358.html So random changes with natural selection is not reality, but more like a smart change.
14. ## Water forms floating 'bridge' when exposed to high voltage

From the page: How high the static voltage has to be or how pure the water has to be is not mentioned, but they do say that dust is probably a reason that makes it unstable It's like liquid ice.
15. ## Water forms floating 'bridge' when exposed to high voltage

http://www.physorg.com/news110191847.html It's cool but weren't we suppose to find something like this about a half-century ago?? I'm mean you don't even need a lab to reproduce this experiment.
16. ## Laser TV/projection technology

Uhm, you didn't read any of it didn't you? Energy consumption will decrease and MTBF increases strongly. 20.000 hours (compared to 2000 lamp hours with current projectors TV's) That is almost 7years for 8 hours every day, by then I will buy something else. P.S. you don't need heat to make laser light.
17. ## Quantum computing more practical now?

an update: http://www.dwavesys.com/index.php?mact=News,cntnt01,detail,0&cntnt01articleid=4&cntnt01origid=15&cntnt01returnid=21
18. ## Quantum computing more practical now?

http://dwave.wordpress.com/2007/01/19/quantum-computing-demo-announcement/ I'm curious... Some info: http://en.wikipedia.org/wiki/NP-complete http://www.nada.kth.se/%7Eviggo/problemlist/compendium.html http://arxiv.org/PS_cache/quant-ph/pdf/0206/0206003.pdf
19. ## Laser TV/projection technology

Hi, It seems that new LED technologies will be past by laser technology in the display market. They even claim the end of plasma TV's. (due to better quality with lower production cost) news: http://www.theage.com.au/news/NATIONAL/Laser-TV-predicted-to-be-death-of-plasma/2006/10/10/1160246121576.html lasers: http://www.novalux.com/ Making a big investment in a new plasma screen could be a bad idea now. They claim to have a first commercial model end 2007.
20. ## Who believes in evolution?

I was just thinking how many people (%) Are actualy educated enough to interprete the presented data and label it true or false. 30% is probably already too much. So that means that 70% of the people base their decision on other people's decision....
21. ## Who believes in evolution?

More interresting than how many say it's true is are their numbers increasing or decreasing. The US is decreasing. And there are still much people who can't decide. Not sure if that is because they didn't understand the question or if they are in doubt.
22. ## good laptop for student

If you later want to install vista on it then it will be a must, now it's just nice for some not common situations. Anyway AMD & Intel started their dual-core price war. Intel made a faster CPU than AMD (since long), AMD is dropping prices fast, Intel also but mostly to get rid of their old CPU. So if you are not in a hurry...
23. ## programs that draw vector fields

You mean like Matlab? edit: Comparing 2D Vector Field Visualization Methods: A User Study http://vis.cs.brown.edu/docs/pdf/Laidlaw-2005-CVF.pdf

You will probaly have an old AGP 4X graphics card slot. I'm even not sure that there is an upgrade for you. Why would you want to upgrade your graphics card, You do realise that a fast card will never reach its potential because your CPU an memory can't follow. (I case you didn't understood it, I'm saying: buy a new PC) Maybe you can get a Nvidia Geforce4 Ti (not MX) on the second hand market This is a DX8 card. I don't think that any DX9 card will work (well) in your PC. http://cgi.benl.ebay.be/Abit-Siluro-NVIDIA-GeForce-4-Ti4200-AGP-128MB-graphics_W0QQitemZ8817886930QQcategoryZ27387QQrdZ1QQcmdZViewItem (You don't really lose a lot if it doens't work wel) P.S. You probably mean 1Ghz cpu clock or 1GB memory instead of 1MB
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