Pictures that leave you Speechless

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Re: Pictures that leave you Speechless

Postby chris.ph » Sat May 12, 2012 3:43 pm

the yanks (obviously) are on about putting rail guns on destroyers :D
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Re: Pictures that leave you Speechless

Postby Quatermass » Sun May 13, 2012 1:14 am

chris.ph wrote:the yanks (obviously) are on about putting rail guns on destroyers :D


They would be. Railguns are accurate and highly destructive. And as I heard somewhere, there is no such thing as "overkill". There is only "open fire" and "I need to reload". :lol:
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Re: Pictures that leave you Speechless

Postby ChristianBecker » Sun May 13, 2012 5:54 am

raptornx01 wrote:what was the supposed matter to energy ratio for anti-matter weapons? something like 1 kilogram of anti-matter equaling the power of 28,000 hiroshima bombs? or to put it another way, close to the power released when Mt. Saint Helens exploded in 1980.


Quite easy to calculate: E = mc² (no, not michelancello) → E = 1kg · 9·10¹⁶m²·s⁻² = 9·10¹⁶ Joule
Nuclear bombs are usually measured in TNT-equivalents: 1kT TNT = 4,184 · 10¹² J; the Hiroshima bomb had a force of about 13.4kT → 9·10¹⁶ Joule /(13.4 · 4,184 · 10¹² J) = 1605.25
So, 1kg of anti-matter would be as powerful as 1605 and a quarter Hiroshima bombs.
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Re: Pictures that leave you Speechless

Postby raptornx01 » Sun May 13, 2012 7:12 am

so a 21.5 megaton bomb? little less then ratios i had read, but still massive.

i never did get that energy equation (or should i say it was never really explained too well), specifically what units of measure you used in the calculation. like in this example kg. and which units of energy it would be converted into.
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Re: Pictures that leave you Speechless

Postby ChristianBecker » Sun May 13, 2012 7:35 am

You use the units that come with the stuff in the formula:
m = mass; SI unit of mass is kg
c = speed of light; SI unit of speed is meters per second = m·s⁻¹
So, after putting it together, the units will be kg · m² : s⁻² (s⁻² = 1/s²)
kg times meter squared divided by second squared = Joule, the SI unit for energy.
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Re: Pictures that leave you Speechless

Postby raptornx01 » Sun May 13, 2012 7:39 am

so no matter the original units for mass used you always convert it to kg?
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Re: Pictures that leave you Speechless

Postby ChristianBecker » Sun May 13, 2012 8:09 am

Yes, you've got to convert at some point in the process, lest you end up like the Mars Orbiter in 1999 http://articles.cnn.com/1999-09-30/tech/9909_30_mars.metric.02_1_climate-orbiter-spacecraft-team-metric-system?_s=PM:TECH.
Alternatively you could use a different formula that has been adapted to be used with lbs and inches. If you end up with Joule as the unit for energy, though, that formula WILL be E = mc² with some converting done.
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Re: Pictures that leave you Speechless

Postby raptornx01 » Sun May 13, 2012 8:57 am

Lol i remember when that happened :lol:

But yeah, thats the bit that was never explained about the equation. Thanks :)
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Re: Pictures that leave you Speechless

Postby Quatermass » Sun May 13, 2012 11:47 pm

ChristianBecker wrote:You use the units that come with the stuff in the formula:
m = mass; SI unit of mass is kg
c = speed of light; SI unit of speed is meters per second = m·s⁻¹
So, after putting it together, the units will be kg · m² : s⁻² (s⁻² = 1/s²)
kg times meter squared divided by second squared = Joule, the SI unit for energy.


I've always wondered. Thanks. :)
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Re: Pictures that leave you Speechless

Postby ChristianBecker » Mon May 14, 2012 5:06 am

Yes, that seems to be a common problem with the equation. Nearly everyone knows it, few people could actually use it. I remember that I, too, also didn't actually know how to use it. As I picked up some physics here and there during my studies, it became clearer.
A large portion of understanding physics is getting the units right. It might seem tedious when teachers at school and tutors, professors etc. at university insist you always write down the units, even when only calculating something trivial like speed or how far an accelerating vehicle gets in a given time. But once you get used to it, a lot of it becomes clear. Units are like numbers which with you can calculate. In the end, when you cancel down the result, you usually get rid of some m, kg, s, etc. and the rest is some handy unit, like m/s, kg · m²/s². Was really an eye opener when I first realized this.
It's also handy in chemistry when calculating the concentration etc. of stuff.
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Re: Pictures that leave you Speechless

Postby raptornx01 » Mon May 14, 2012 9:03 am

I must have seen that equation thousands of times, or more, in my life. And not just when its thrown out there out of context by someone who doesn't know any better (like how the famous "Romeo, Romeo, where art thou Romeo" line is never used right since the line is actually asking his name, not where he is). I've seen it in school and out of school. I've seen it science specials, in docs about physics in general, or Einstein specifically. but never has anyone said what it meant (beside the basic Energy equals mass times the speed of light squared).

its like they are saying either "any idiot should know what it means" or "don't worry your pretty little head about it, its too complicated for you"
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Re: Pictures that leave you Speechless

Postby Dotsie » Mon May 14, 2012 10:42 am

raptornx01 wrote: like how the famous "Romeo, Romeo, where art thou Romeo" line is never used right since the line is actually asking his name, not where he is

The arguments I've had about that one :lol: (BTW it's wherefore, which means why, not where)
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Re: Pictures that leave you Speechless

Postby raptornx01 » Mon May 14, 2012 12:03 pm

i was close :lol:
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Re: Pictures that leave you Speechless

Postby raisindot » Mon May 14, 2012 12:35 pm

raptornx01 wrote:so no matter the original units for mass used you always convert it to kg?


Uh, speaking of images that you leave you speechless, just exactly is that little cartoon girl doing in your sig image, Raptor? :D
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Re: Pictures that leave you Speechless

Postby raptornx01 » Mon May 14, 2012 1:08 pm

can't stop rockin' :lol: :character-beavisbutthead:
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