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Energy-Mass equivalence

  1. May 9, 2004 #1
    Is there any model to describe the mechanism that allows matter to be converted into energy? If a mass is suddenly converted into its energy equivalent what is the nature of this energy?
     
  2. jcsd
  3. May 9, 2004 #2

    mathman

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    When mass in converted into energy it typically comes out as electromagnetic radiation, although some of it might be in the kinetic energy of the particles (if any) that result from the reaction. Examples: positron-electron collsion leads to 2 511 kev gamma rays, nulclear fission leads to two nuclides plus neutrons plus gamma rays.
     
  4. May 9, 2004 #3
    Thanks for the post. Any references to the statement that the mass energy is converted to electromagnetic radiation?
     
  5. May 10, 2004 #4

    mathman

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    http://atom.kaeri.re.kr/ton/

    The above is a table of all nuclides, including specifically the decay information about those that are radioactive. Any good book on nuclear physics would help also.
     
  6. May 10, 2004 #5

    russ_watters

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    Google for "nuclear bomb..."
     
  7. May 10, 2004 #6
    A search that would likely prove to contain much interesting information, perhaps not only to the people interested in particle physics. It's kind of off topic, but I have to wonder if such searches will gain unwelcome attention from beaurocrats overzealous to see everything as terrorist threats. Is it just me, or is anyone else concerned?
     
  8. May 11, 2004 #7
    When it is said that mass is converted into energy it is meant that the energy changes from one form to another form. The total energy, like the total mass, remains constant. The form of the energy, and the form of the mass, changes. The form can go from potential energy to kinetic energy or radiant energy etc. Take the nucleus of an atom as an example. Classically you can think of the mass of the nucleus consisting of the rest mass of the individual particles plus the potential energy of the particles plus the kinetic energy of the particles. When the nucleus decays then what was potential energy changes to kinetic energy or radiant energy etc. The total mass remains constant though.

    For a solid worked example please see

    http://www.geocities.com/physics_world/sr/nuclear_energy.htm

    Pete
     
  9. May 12, 2004 #8
    When you push two protons towards each other there is an increase in potential energy. If energy and mass are equivalent is there a loss in mass of the system due to the increase in PE in order to preserve energy conservation?
     
  10. May 12, 2004 #9

    Doc Al

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    No. You are adding energy to the system, which increases its mass.
     
  11. May 12, 2004 #10
    If this is the case you violate conservation of energy.
     
  12. May 12, 2004 #11
    I don't think so, because you are doing work (adding energy to the system) to push them together... The energy would be lost from whatever is pushing them together.

    ...right?
     
  13. May 13, 2004 #12
    this is true

    also, you're not necessarily adding mass to the system when you give it energy

    just because energy and mass are equivalent doesnt mean they are the same

    for example,
    5-2 is equivalent to 3 but not the same as 3
     
  14. May 13, 2004 #13

    jcsd

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    It isn't, if the system was closed it would be.
     
  15. May 13, 2004 #14

    Doc Al

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    Nope. Conservation of energy applies to a closed system. Obviously the system isn't closed if an outside agent can do work on it.

    oops: jcsd beat me to it.
     
  16. May 14, 2004 #15
    When you push two protons together then that work is at the expense of another part of the system or at the expense of another form of energy. E.g. if two protons are on a collision course and then stick together then the potential energy is increased at the expense of the original kinetic energy of the particles. The mass of the system remains constant though.

    Pete
     
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