Protons are stable, but free neutrons decay because:

  1. neutrons have no quarks
  2. neutrons are leptons
  3. protons have more quarks
  4. a d quark can change into a u quark, and the proton has lower mass
Answer

D) a d quark can change into a u quark, and the proton has lower mass

Weak decay. SLO P-11-F-20 · Understanding

Physics MCQ · More Nuclear and Particle Physics MCQs · Practise