The sum of the charges of the quarks in a particles gives the overall charge of the particles. Two up quarks and a down quark make a proton, which has a charge 1. On the other hand, two down quarks and an up quark make a neutron, which has a charge 0. What is the charge of an up quark?

Question

I have no idea how to solve this. I'm assuming that I would make a system of equations, since that is what we're learning about. And what is a quark? Thank you so much!

Answer 1

2 u + d = 1
u + 2 d = 0
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2 u + d = 1
2 u + 4 d = 0
---------------- subtract
0 u - 3 d = 1
d = -1/3

u -2/3 = 0
u = 2/3

and a quark is something two ups and a down of which make a proton :)