A Level Physics Practice Exam

What is the quark configuration of a proton?

1. Up, Down, Down

2. Up, Up, Up

3. Up, Up, Down

4. Down, Down, Up

The correct answer is: Up, Up, Down

The quark configuration of a proton is composed of two up quarks and one down quark, represented as "Up, Up, Down." This configuration is fundamental to the definition of a proton, which is a baryon, a type of subatomic particle found in the nucleus of an atom. Protons carry a positive charge, which can be understood in terms of their quark composition: each up quark has a charge of +2/3, and each down quark has a charge of -1/3. Therefore, the total charge of a proton can be calculated as follows: - Charge from the two up quarks: 2/3 + 2/3 = +4/3 - Charge from the one down quark: -1/3 Adding these contributions together gives: +4/3 - 1/3 = +3/3 = +1 This matches the observed positive charge of a proton. The other configurations listed include variations of up and down quark counts that do not correspond to the charge or known properties of a proton. The presence of two up quarks and one down quark is crucial to defining not just the charge, but also the stability and interactions that characterize protons