Kicking question

[SamG]

OK, I'm only a fan, but I've got a rule question I'm hoping you guys can explain (sorry I don't know all the correct abbreviations)...

Situation 1: Team A punting from their 20 yardline. Punt comes down at the 50, hits A88, and continues on to the B40. Where is the ball spotted?

Situation 2: Team A punting from the 50. Punt comes down at B2, hits A88, and continues into the EZ. Where is the ball spotted?

My untrained (aside from watching as a fan) brain says #1 is @ the 50 for B. #2 is at the B20 (touchback).

IF I am correct (absolutely no guarantee of that), why? Both involve touching the ball by the kicking team with the only difference being the location on the field. If I am incorrect (probable), please set me straight.

Thank you in advance.