Mailing List Archive

Re: [LoGH] The gearheads attack =)

Walter Amos (amos@sedl.org)
Fri, 13 Oct 2000 17:43:30 -0500 (CDT)


On Thu, 12 Oct 2000, Josh Yuan wrote:

> 120 MW = a few hundred gigajoules of energy.(300~ ?,
> physics major with the W->J conversion?) So even if
> the beam lost 95% of its energy at max range, that is
> still a few gigajoules of energy. I am assuming a 1
> sec firing period.

Remember: POWER = ENERGY / unit time!  Thus your above conversion W->J
isn't quite correct, since Watts are a unit of Power, and Joules are a
unit of energy.  In fact, by definition, 1 Watt = 1 Joule/second!  

(...oh, I overlooked that you said a 1-second firing period...
anyway... your joules estimate is incorrect)

120MW = 120 MegaWatts = 1.2x10^8 Watts = 120 million Joule/second,
= 0.12 gigaJoule/sec

Your handy-dandy Energy and Power units conversion chart:

1 Joule = 10^7 erg = 0.239 calorie = 0.738 ft.lbs = 2.78x10^-7 kW.hours

1 electron-Volt (eV) = 1.6x10^-19 Joule = 1.6x10^-12 erg

1 horsepower = 746 Watts = 550 ft.lb/sec

And, for those wanting to calculate nuclear yields, here is the energy
equivalence of mass according to E=mc^2:

1 kg = 8.897x10^16 Joule

...so if I could find the amount of energy released per ton of TNT
explosion, I could work out the number of Megatons per unit mass of
total matter conversion (so you could say an X pounds antimatter bomb
would yield Y Megatons of energy)...

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"Zu jeder Zeit, an jeder (sic) Ort, bleibt das Tun    |       Walter Amos
  der Menschen das gleiche..." - Galactic Heroes II   |    amos(at)sedl.org