The Standard Model and the Four Interactions · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

The particle catalogue and its rules

Science · Quantum & Modern Physics · ages 20-22
Name ______________________   Date ____________

  1. Why does the weak force reach almost no distance?

    • Its W and Z carriers are very massive
    • It has no carriers at all
    • Photons block its path

  2. Which exchange particle carries each quantum force?

    • Gravitons carry all three
    • Gluons strong, photons EM, W and Z weak
    • W and Z carry all three

  3. Leptons feel the strong force.

    Circle one:   True   False

  4. How do a proton and a pion differ in quark content?

    • Both hold three quarks
    • Proton is three quarks, pion is quark plus antiquark
    • Both are quark plus antiquark

  5. A neutron decaying into only an electron plus a positron breaks which rule?

    • Charge
    • Momentum
    • Baryon number

  6. A baryon holds how many quarks? Type the count.

    Answer: ______________

  7. Check baryon number for pion minus plus proton giving pion zero plus neutron plus pion minus plus pion plus. Allowed?

    • Allowed: baryon number stays 1
    • Forbidden: baryon number rises to 2
    • Forbidden: baryon number falls to 0

  8. A student calls the photon a strong-force carrier. What is wrong?

    • Photons do not exist
    • Carriers cannot be named
    • Photons carry electromagnetism; gluons carry the strong force
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Answer key

For grown-ups. Fold this page away before handing over the rest.

The particle catalogue and its rules W1-mt_GYB4UMS0D9-s1

  1. Its W and Z carriers are very massive · Massive carriers live briefly, so they travel almost nowhere.
  2. Gluons strong, photons EM, W and Z weak · Each force has its own carriers: gluons, photons, and W with Z.
  3. False · Only quarks carry color charge, so leptons skip the strong interaction.
  4. Proton is three quarks, pion is quark plus antiquark · Protons are baryons with three quarks; pions are mesons with a pair.
  5. Baryon number · Charge still balances, but baryon number falls from 1 to 0.
  6. 3 · Baryons team three quarks, as in protons and neutrons.
  7. Allowed: baryon number stays 1 · Reactants tally 0 plus 1, products tally 0 plus 1 plus 0 plus 0: still 1.
  8. Photons carry electromagnetism; gluons carry the strong force · Each carrier serves its own force, and the photon serves EM.
Worksheet · LightMySky