how come you guys don't have problems 62 thru 81 ?

Hi bydand,

Thank you very much for getting in touch. The questions 62 to 81 are in the "General Problems" section, and I cover just the questions in the "Problems" section. Making 1675 videos was very time consuming, so we had to make this decision to keep the time commitment manageable, and I'm hoping that this meets most of the needs of most students.

All the best with you studies, and please don't hesitate to get in touch further,
Shaun Dychko

Wouldn't the direction be dependent on how you assigned the directions of the electron and neutrino?

Hello thesouthportschool, you're quite right. The choice of direction is up to the problem solver, with the only thing we know for sure being that the neutrino and electron are at right angles. This is mentioned briefly at 0:27 in the video.

All the best,
Mr. Dychko