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Nucleons consist of quarks which are charged particles. Proton has the quark content of uud and neutron of udd. So, it may be visualized that the down quark always remain between the up quarks inside proton and the up quark remains between the down quarks inside the neutron. Are these quarks stationary inside protons or neutrons? (if yes, why and how is it so?) Or, the up quarks rotate around the down quark in proton and the down quarks around the up quark in neutron? (if so, do they move along the same orbit?)

Subhra
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    possible duplicate of What's inside a proton? – Emilio Pisanty May 15 '15 at 15:58
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    For a comprehensive answer how quarks are "inside" nucleons, see DavidZ's answer to the question EmilioPisanty linked. On a less comprehensive note, asking for the "motion" of quarks inside nucleons is as meaningless as asking for the "motion" of electrons around the nucleus of an atom - neither electrons nor quarks "move" in the classical sense, we are at scales where quantum effects dominate and we shouldn't trust our classical visualizations. – ACuriousMind May 15 '15 at 16:06
  • @EmilioPisanty I have read it including the answer recommended by ACuriousMind, it seems that all sorts of particles reside inside a proton in a very chaotic manner. Therefore, we cannot have any rule (if I have understood correctly) to describe the insight of a proton. At various energy states various particles inside it get revealed. So, whenever, we need to find any new particle, we should look into it at various energy levels. – Subhra May 15 '15 at 16:56
  • That's essentially correct (though the matter is more subtle than that, as DavidZ explains in his answer). – Emilio Pisanty May 15 '15 at 17:38
  • Hi. As ACuriousMind said. May I ask you what's the motion of an electron in an atom-I mean how do you think it or imagine it? – Constantine Black May 15 '15 at 17:45
  • @ConstantineBlack You can consider nucleus to be at the center and the electrons are moving around it in certain allowed orbits. I expected the U quarks to move around the D quark in proton. – Subhra May 16 '15 at 04:10
  • I don't think we should use such description unless for communicating reasons. I don't think the ''movement'' down there can be described somehow with classical pictures. The electrons don't move around certain orbits- that's a simplification made for didactical(I think wrongly) and communicative reasons. For example in hydrogen- what does it mean to have the electron moving around the proton when the orbital angular momentum quantum number is 0(l=0)? – Constantine Black May 16 '15 at 10:25

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Supposedly quarks are in a well but experience minimal or no force at close range, called asymptotic freedom. If it is assumed that a quark model can be used where they are treated as "Point" particles, then they should be like three particles in a well. If QCD is believed then they are in different "color" states so can be in the same particle-in-a-well ground states. This could still be true if "bag models" are used instead of QCD.

Rabi
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