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The meaning of the relative strength of forces

  1. Feb 26, 2009 #1
    It's common to hear people say that gravity is a "weak force" and that it is "32 times weaker than the weak nuclear force." But what does that even mean, if it has any meaning at all. The gravity on a particle is proportional to its mass. The electric force on an object is proportional to its charge. To make a statement about relative strengths, that would mean you're making an implicit statement about the relationship between an object's charge and mass, right?
  2. jcsd
  3. Feb 26, 2009 #2


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    Here's a simple illustration using simplifed forms of the gravitational and electric forces:



    If we compare the constants of proportionality, k and G, we find that k=10^20 G. It's basically saying that per whatever unit the force uses to measure its strength, one force is much stronger than another.
  4. Feb 26, 2009 #3
    Yeah, but that's comparing apples (mass) to oranges (charge). The units are different, so you can't simply divide and find the ratio of the strengths... you're left with a conversion factor of kg/C or something.
  5. Feb 26, 2009 #4


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    You are of course right. That example was pretty terrible and I was making light of what is a much more complicated situation. I don't fully understand this myself but after looking around I think it has something to do with the relative coupling constants for the four fundamental forces.

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