Neutrino

Neutrinos are required content in the rewritten AP Physics 2 course, which surprises anyone working from an older book. Essential knowledge 15.8.A.1.ii: neutrinos and antineutrinos are subatomic particles that have no electrical charge, have negligible mass, and are symbolised by $\nu$ and $\bar{\nu}$ respectively.

Statement 15.8.A.1.iii adds the reason nobody notices them. They interact with matter only via the weak force and the gravitational force, which results in very little interaction with normal matter.

In a decay equation they carry 0 in the mass-number column and 0 in the charge column, so they change no daughter nucleus. They are written anyway because 15.8.A.2.i makes lepton number conserved along with nucleon number and charge. Which one goes where is fixed by 15.8.A.2.iii and 15.8.A.2.iv: an antineutrino leaves with the electron in beta-minus decay, a neutrino leaves with the positron in beta-plus.

Now read the boundary statement, because it is unusually generous. Topic 15.8 says types of neutrinos, the characteristics that distinguish neutrinos and antineutrinos, and an explanation or application of the weak force are not within the scope of this course. So the exam can ask you to place $\bar{\nu}$ correctly in an equation, and cannot ask you what makes it an antineutrino. Flavours, oscillation and mass limits are all off the table.

One handwriting warning. The Greek $\nu$ looks like a $v$, and a $v$ in the same problem is a speed. Write them differently before you need to.