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Colour force

  1. Apr 29, 2006 #1
    My (high school) physics teacher was telling us about quarks and how the colour force between quarks is responsible for the strong nuclear force among baryons. He also claimed that unlike other forces, this force became stronger over a distance which is why it requires alot of energy to separate quarks. I do not understand how it is possible to have a force that becomes stronger as distance increases. If this is so, how is it possible to to have protons and neutrons not bound to the nucleus? Wouldnt it be impossible to ever supply enough energy to have free baryons? Did my teacher incorrectly describe the distribution of the strong nuclear force?
    Last edited: Apr 29, 2006
  2. jcsd
  3. Apr 29, 2006 #2

    Doc Al

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    Realize that the strong nuclear force is a very short-range force. Outside of a certain distance (typical nucleon separation distances) the force quickly dies off.
  4. Apr 29, 2006 #3
    It becomes stronger over an increase in distance to a certain point then dies off? That would seem to make more sense.
  5. Apr 29, 2006 #4

    Doc Al

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    That's right. At very close distances the force is highly repulsive. As distance increases, it becomes more and more attractive. After reaching a maximumum attractiveness, it begins to die off rapidly with greater distance.
  6. Apr 29, 2006 #5


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    As Doc All explained, it increases over a hort distance range and then dies off quickly.

    If you want to have a mental picture, think of a rubber band. Think of the quarks as being little beads attached at the ends of the rubber band. If they are very close, the force is very small. As you pull the beads apart, the force increases (pulling them back together). If you pull too much, the rubber band snaps and the force goes to zero. (the difference though is that in the case of quarks, when the equivalent of the rubber band snaps, the energy stored in the rubber band is converted into mass (thik of E=mc^2) and it creates two new quarks at the extremities of the rubber bands that snapped, ''repairing'' the rubber band there. So when the rubber bands snaps, you end up with *two* rubber bands each with two quarks attached (so for a total of 4 quarks). The end result is that the energy you put in in stretching the rubber band has been converted into mass of the new quarks. This is why also one never sees an isolated quark, a quark alone.

    Hope this makes sense

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