Physics 9702 · AS & A Level · Fundamental particles
Fundamental particles — practice question
A caesium-137 nucleus ($^{137}_{55}\text{Cs}$) decays by sending out a $\beta^-$ particle, creating a nucleus of element X and an antineutrino. The decay is written as $^{137}_{55}\text{Cs} \rightarrow \; ^Q_S\text{X} + R\,\beta^- + ^0_0\bar{\nu}$.
(a(i))[2]
State the value shown by each of the letters P, Q, R and S.
(a(ii))[1]
State the name of the particle category to which the $\beta^-$ particle and the antineutrino belong.
(b)
Particle Y has the quark composition $ddd$, where $d$ stands for a down quark. Particle Z has the quark composition $\bar{u}d$, where $\bar{u}$ stands for an up antiquark.
(b(i))[2]
Show that particles Y and Z have equal charges.
(b(ii))[2]
State and explain which particle is a meson and which particle is a baryon.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Correct answers $P=0$, $Q=137$” …