ridgey Posted August 7, 2005 Share Posted August 7, 2005 In the famous equation, how is c the velocity of light expressed? How do you express velocity, without a refrence to distance or time? Link to comment Share on other sites More sharing options...
NeonBlack Posted August 7, 2005 Share Posted August 7, 2005 Short answer: C is invariant. This basically means that the speed of light is the same in all reference frames. Link to comment Share on other sites More sharing options...
ridgey Posted August 7, 2005 Author Share Posted August 7, 2005 ok, But what is the number? how do we express velocity? Link to comment Share on other sites More sharing options...
insane_alien Posted August 7, 2005 Share Posted August 7, 2005 C=~300000000m/s Link to comment Share on other sites More sharing options...
ridgey Posted August 7, 2005 Author Share Posted August 7, 2005 Thanks. The next question is, how do we express m (mass) is it just in grams? Link to comment Share on other sites More sharing options...
NeonBlack Posted August 7, 2005 Share Posted August 7, 2005 velocity in meters per second and mass in kilograms gives you energy in joules. Link to comment Share on other sites More sharing options...
ridgey Posted August 7, 2005 Author Share Posted August 7, 2005 thank you very much Link to comment Share on other sites More sharing options...
ridgey Posted August 7, 2005 Author Share Posted August 7, 2005 Is this correct? the amount of energy contained in 1kg of matter 1*(300000000*300000000)=90000000000000000joules. Link to comment Share on other sites More sharing options...
Severian Posted August 7, 2005 Share Posted August 7, 2005 Yes. It would be nice to write 9x1016J though. Link to comment Share on other sites More sharing options...
ydoaPs Posted August 7, 2005 Share Posted August 7, 2005 it's not completely right...momentum... Link to comment Share on other sites More sharing options...
Dave Posted August 7, 2005 Share Posted August 7, 2005 I think we can safely assume that the block is stationary in this case. Link to comment Share on other sites More sharing options...
ydoaPs Posted August 7, 2005 Share Posted August 7, 2005 stationary relative to what? Link to comment Share on other sites More sharing options...
ydoaPs Posted August 7, 2005 Share Posted August 7, 2005 [math]E^2=(mc^2)^2+({\rho}c)^2[/math] Link to comment Share on other sites More sharing options...
Kniteli Posted August 8, 2005 Share Posted August 8, 2005 Now how to tap to tap all that energy, oh the wonders.. Link to comment Share on other sites More sharing options...
ydoaPs Posted August 8, 2005 Share Posted August 8, 2005 fission, fusion, matter/antimatter anhialation Link to comment Share on other sites More sharing options...
insane_alien Posted August 8, 2005 Share Posted August 8, 2005 pogos just imagine that the block is in a universe all by its self and is stationary relative to the universe(assume its a universe where you canfind the centre easily) Link to comment Share on other sites More sharing options...
danny8522003 Posted August 8, 2005 Share Posted August 8, 2005 Is this correct?the amount of energy contained in 1kg of matter 1*(300000000*300000000)=90000000000000000joules. In nuclear weapons, only a very very tiny amount of the actual material used in the bomb is converted to energy. Im not sure of the exact figure but i think it was only a few grams. Link to comment Share on other sites More sharing options...
JSKrimmel Posted August 8, 2005 Share Posted August 8, 2005 In nuclear weapons, only a very very tiny amount of the actual material used in the bomb is converted to energy. Im not sure of the exact figure but i think it was only a few grams. I did some rough calculations and using estimates of energy yields, determined approximately the amount of mass that was converted into energy for both the Little Boy dropped on Hiroshima and the Fat Man dropped on Nagasaki. The Little Boy was composed of uranium-235 and although the critical mass, or the mass needed to sustain a chain reaction, for U-235 is 50 kg, only approximately 0.6043 grams were converted to energy. The Fat Man, made of plutonium-239, had a critical mass of only 10 kg yet only between 0.9297 and 1.162 grams of plutonium were actually converted to energy. Link to comment Share on other sites More sharing options...
danny8522003 Posted August 8, 2005 Share Posted August 8, 2005 Ah i remember now - that sounds about right. That's not a lot of mass considering the size of the explosions :\ Link to comment Share on other sites More sharing options...
JSKrimmel Posted August 8, 2005 Share Posted August 8, 2005 Living in a world so advanced in technology and so overwhelmed with conflict makes those numbers seem even smaller. An extension of the calculations above using rather conservative death toll estimates shows that on the average it took only 7.470 micrograms (10^-6 g) to kill a single person in Nagasaki and just 4.316 micrograms per individual with the more efficient uranium bomb dropped on Hiroshima. (To put it in perspective, each fragment of a paperclip cut into one million pieces would weigh one microgram.) One can only imagine what 60 years of scientific advancement has done to those figures. Link to comment Share on other sites More sharing options...
swansont Posted August 8, 2005 Share Posted August 8, 2005 Living in a world so advanced in technology and so overwhelmed with conflict makes those numbers seem even smaller. An extension of the calculations above using rather conservative death toll estimates shows that on the average it took only 7.470 micrograms (10^-6 g) to kill a single person in Nagasaki and just 4.316 micrograms per individual with the more efficient uranium bomb dropped on Hiroshima. (To put it in perspective' date=' each fragment of a paperclip cut into one million pieces would weigh one microgram.) One can only imagine what 60 years of scientific advancement has done to those figures.[/quote'] 60 years of scientific advancement hasn't changed the speed of light... Link to comment Share on other sites More sharing options...
danny8522003 Posted August 8, 2005 Share Posted August 8, 2005 Lol i think he means the amount of mass used up in the explosions. It's efficiency i think. Link to comment Share on other sites More sharing options...
swansont Posted August 8, 2005 Share Posted August 8, 2005 Lol i think he means the amount of mass used up in the explosions. It's efficiency i think. The efficiency of how much energy you get from a set amount of mass is given by c2 OTOH, you could become more efficient by converting a higher fraction of the bomb's mass to energy, but those relevant numbers aren't the ones that were quoted, as far as I can tell. Link to comment Share on other sites More sharing options...
JSKrimmel Posted August 9, 2005 Share Posted August 9, 2005 Naturally I meant that the mass converted into energy would be increased by 60 years of scientific advancement. For example, I know that separating U-235 isotopes was a major challenge. 60 years of advancement would allow for more pure samples of U-235 to be separated, potentially making a more destructive bomb by increasing the amount of mass converted to energy. Also, a bound on the size of the atomic bomb was the weight allowance of the airplane used to transport it. Today's larger bombers obviously have larger payloads and would be able carry approximately 3 times more weight than the Enola Gay. A bigger bomb would allow for more mass to be converted to energy, making the bomb deadlier still. The point that I was trying to make is that there are many scenarios we can come up with that would allow for more mass to be converted to energy. I apologize for not being more explicit. Link to comment Share on other sites More sharing options...
jcarlson Posted August 9, 2005 Share Posted August 9, 2005 You forgot to mention the ICBMs on Subs... each sub can hold up to 24 ballistic missiles with up to 10 warheads on each, with each warhead capable of leveling a city. Did you know that if a SSBN was its own country, it would be the third largest nuclear power in the world? (after the US and Russia) Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now