In the quark model of fundamental particles, a proton is composed of three quarks: two “up” quarks, each having charge , and one “down” quark, having charge . Suppose that the three quarks are equidistant from each other. We can take the distance this distance to be . We will calculate (a) the potential energy of the interaction between the two “up” quarks and (b) the total potential energy of the system.

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(a)

Distance between the two “up” quarks, a, is .

Charge of each “up” quark, q, is .

Therefore, the potential energy of the two “up” quarks will be

(b)

The total electric potential energy of the 2 “up” and 1 “d” quark system will be