Physics 9702 · AS & A Level · Atoms, nuclei and radiation
Atoms, nuclei and radiation — practice question
A nucleus P, initially at rest and of mass $243\,\text{u}$, undergoes decay by releasing an $\alpha$-particle of mass $4\,\text{u}$, producing a different nucleus Q, as shown in Fig. 7.1. The $\alpha$-particle leaves with an initial speed of $1.6 \times 10^{7}\,\text{m s}^{-1}$.
(a)[2]
Use the principle of conservation of momentum to explain why nucleus Q and the $\alpha$-particle initially move in opposite directions.
(b)[2]
Determine the initial speed $v$ for nucleus Q.
(c)[3]
Calculate the initial kinetic energy of the $\alpha$-particle, in MeV.
(d(i))[2]
On Fig. 7.2, mark nucleus R with a cross and label that cross R, then mark nucleus S with a cross and label that cross S.
(d(ii))[1]
State the name of the other lepton, besides the $\beta^-$ particle, that is emitted when nucleus R decays.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “total momentum before decay is zero / P is at rest” …