# Kedas

Senior Members

695

1. ## Little or no wildlife animals dead in Sri Lanka

http://www.alertnet.org/printable.htm?URL=/thenews/newsdesk/COL136356.htm Seems the wildlife animals used their instincts right. (unlike most humans)
2. ## Booting error

what sounds do you have when you start it up then look if you find the answer in this table: http://www.computerhope.com/beep.htm
3. ## mass centre of a half sinus?

Thanks for the full explanation I'm sure that I can figure it out for myself next time
4. ## mass centre of a half sinus?

M the surface is 2 but I fail to see the simplifying to y² = sin²(x) anyway it looks OK so thanks for your help. my math is failing me.
5. ## mass centre of a half sinus?

This sure can be correct and which program did you use for it?
6. ## mass centre of a half sinus?

I know the formula but I was hoping someone already did the double integrals and simplefied it. (I expect something simple) btw I got integral ((y+cos(Z)) * Z * tg(Z)).dZ (Z from pi/2 to 0, with y the constant I'm looking for) but I serioulsy doubt it's correct, since I made it

8. ## mass centre of a half sinus?

I mean 0 to pi , only the first half of one full sinus. consider a plate that has that shape, at which point would I have to hang it so it would stay flat. (centre of mass)
9. ## Monster Quake & Tsunami off Sumatra

you mean on the coast? I heard a withnes say that just before it the sea pulled back for about 500meter so that's more or less an indication for a half period I guess.

11. ## mass centre of a half sinus?

Hi, Does someone know where the mass centre of a half sinus period is located? I know pi/2 on the x-axes but on the y-axes ? to give an idea for a half circle it's located at R*4/(3*pi) that is 0.42 for R=1
12. ## Monster Quake & Tsunami off Sumatra

I agree on never a wall of water on open sea but you sure have big waves there. lookup some big storm statistics if you like.
13. ## Monster Quake & Tsunami off Sumatra

it's meters not centimeters. http://ruby.colorado.edu/~smyth/G1010/17OceansHO.PDF here they talk about 0.5-2meters but storms with 14meters and more have been seen in open sea.
14. ## Monster Quake & Tsunami off Sumatra

300MPH that would mean a wave length of about 10km. wave= 2*pi*v^2 / g (for deep water)
15. ## Monster Quake & Tsunami off Sumatra

depends, for very long ships this could be dangerous for small ships it won't when it approuces the coast de amplitude will rise fast and the depth/wave-length is decreasing making it very dangerous because it's almost like a wall of water. Why dangerous for big ships: because the front and back can be located at the tops of a wave while the middle of the ship has no support at all this can make the ship to crack up. more or less the same can happen on the top of a wave. So the relation wave length and length of the ship are important and obviously an amplitude that is high enough to lift it out of the water.
16. ## Asteroid impact predicted in 2029

I know that but saying 'what is the chance that the chance is right' isn't that a bit of a 'wrong' question.

18. ## How to calc. the Energy of a big water wave?

yeah but my queston was which one, it's not like there is only one object moving at a constant speed.
19. ## How to calc. the Energy of a big water wave?

and what is v? (water isn't moving horizontally until it reach the coast)
20. ## How to calc. the Energy of a big water wave?

Hi I was wondering how big/small would an asteroid have to be to generated about an equal devestating effect as the earthquake (8.9) if it woud impact at the same place. The earthquake energy is about 48 million tons of TNT (if I'm correct) (assuming 6 million tons of TNT= 8 on the Richter scale) So it are actualy two questions: - size of an incoming asteroid based on this link that would be less than 75meters http://www.astronomycafe.net/qadir/q975.html - how to calulate the energy contained in a wave of water? correction: Richter scale isn't a factor 10 but 10^1.5 so the energy would be more likely about 1412000TJ or 3374 Megatons. also Richter scale 8 is more like 15 Megatons accorfing to this site. http://www.geop.itu.edu.tr/~onur/seis/energy.html
21. ## controlling dreams and when you wake up

You could control your dreams and the first thing you do is trying to fly to the sun?!? Well, more comment isn't needed I guess (just kidding)
22. ## problem: sin(10^40)

For those interested: I kept the calculation accuracy of it high but added a pi that wasn't that accurate you can see that only at accuracy 41 we are getting close/stable. with maple 8: you get pi followed with the result of the calculation. sin(10^40-2*p*10^39) with p=Pi > p:=evalf(Pi,70) accuracy=70 > p:=evalf(Pi,70); > evalf(sin(10^40-2*evalf(p,70)*10^39),70); p:=3.141592653589793238462643383279502884197169399375105820974944592307816 -0.5696334009536363273080341815742365755028674749735871234233590307534688 > p:=evalf(Pi,50); > evalf(sin(10^40-2*evalf(p,50)*10^39),50); p := 3.1415926535897932384626433832795028841971693993751 -0.56963340096320483302155351446748255175004957983385 > p:=evalf(Pi,46); > evalf(sin(10^40-2*evalf(p,50)*10^39),50); p := 3.141592653589793238462643383279502884197169399 -0.56963401755159324178758070546326680727163521628658 > p:=evalf(Pi,44); > evalf(sin(10^40-2*evalf(p,50)*10^39),50); p := 3.1415926535897932384626433832795028841971694 -0.56963237375352485248115648847294557616382230212022 > p:=evalf(Pi,43); > evalf(sin(10^40-2*evalf(p,50)*10^39),50); p := 3.141592653589793238462643383279502884197169 -0.57028971108410160238203260125675586427898889887725 > p:=evalf(Pi,42); > evalf(sin(10^40-2*evalf(p,50)*10^39),50); p := 3.14159265358979323846264338327950288419717 -0.56864568433037894515920937125020327441117069451661 > p:=evalf(Pi,41); > evalf(sin(10^40-2*evalf(p,50)*10^39),50); p := 3.1415926535897932384626433832795028841972 -0.51829708252841365579298072494084993238214196173488 > p:=evalf(Pi,40); > evalf(sin(10^40-2*evalf(p,50)*10^39),50); p := 3.141592653589793238462643383279502884197 -0.81041404149828340893644116133287541019985461015021 > p:=evalf(Pi,39); > evalf(sin(10^40-2*evalf(p,50)*10^39),50); p := 3.14159265358979323846264338327950288420 -0.94183316470675507802643727766602357848601285229868 > p:=evalf(Pi,37); > evalf(sin(10^40-2*evalf(p,50)*10^39),50); p := 3.141592653589793238462643383279502884 0.78071915409033291423119565202296953326898213238585
23. ## Math computer programs???

They are usually standard software for students (student version). So if you know someone, ask. These version are much cheaper but don't support all features but for most (non Pro) people they aren't needed. It are big programs so very unlikely you will find a copy on the net. (1 or 2 CD's)
24. ## Boost Brainpower

No I didn't, I wouldn't have made a point based on this data.

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