(a) In a quark model of elementary particles,


(a) In a quark model of elementary particles, a neutron is made of one up quarks and two down quarks. Assume that they have a triangle configuration with side length of the order of 10-15 m. Calculate the electrostatic potential energy of neutron and compare it with its mass 939 MeV.

(b) Repeat above exercise for a proton which is made of two up and one down quark.


There are three charges in the system. The potential energy of the system is equal to the sum of the PE of each pair.

U = 1/4 π ε0 {qdqd/r – quqd/r – quqd/r}

Substituting the values we get,

U = 5.11 10-4

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