Eduqas A-Level Physics A420QS
Basic Physics
Kinematics
Dynamics
Energy Concepts
Circular Motion
Vibrations
Kinetic Theory
Thermal Physics
Conduction of Electricity
Resistance
D.C. Circuits
Capacitance
Solids Under Stress
Electrostatic and Gravitational Fields of Force
Using Radiation to Investigate Stars
Orbits and the Wider Universe
The Nature of Waves
Wave Properties
Refraction of Light
Photons
Lasers
Nuclear Decay
Particles and Nuclear Structure
Nuclear Energy
Magnetic Fields
Electromagnetic Induction
Option A: Alternating CurrentsOption A
Option B: Medical PhysicsOption B
Option C: The Physics of SportsOption C
Option D: Energy and the EnvironmentOption D
Mathematical Requirements (Appendix C)
Particles and Nuclear Structure
Quark composition of the proton, neutron and pions
- 3 things to know
- Component 3
Overview
Recall questions on the charges of the first-generation quarks, the compositions of the proton and the neutron and the charge arithmetic that confirms them, the compositions of the charged pions, antiparticle compositions, and why no quark is ever found alone.
What you need to know
Answer each one before you reveal it.
Give the quark composition of a neutron.
Give the quark composition of an antiproton.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Give the quark composition of a proton.
Model answer
A proton is two up quarks and a down quark, written uud. Its charge is +2/3 + 2/3 − 1/3 = +1e.
- 2
Give the quark composition of a neutron.
Model answer
A neutron is one up quark and two down quarks, written udd. Its charge is +2/3 − 1/3 − 1/3 = 0.
- 3
Show that the baryon number of a proton is +1.
Model answer
Each of the three quarks in uud carries a baryon number of +1/3. Adding +1/3 three times gives +1.
- 4
Give the quark composition of an antiproton.
Model answer
An antiproton is ūūd̄, two anti-up quarks with an anti-down quark. Its charge is −2/3 − 2/3 + 1/3 = −1e.
- 5
Give the quark composition of an antineutron.
Model answer
An antineutron is ūd̄d̄, one anti-up quark with two anti-down quarks. Its net charge is zero and its baryon number is −1.
- 6
Give the quark composition of the π⁺ meson.
Model answer
The π⁺ is ud̄, an up quark with an anti-down quark. Its charge is +2/3 + 1/3 = +1e.
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