Momentum applies only to the interception or recovery of an opponent's forward pass, fumble or backward pass. Has nothing to do with kicks, free or scrimmage.
Hm. That's not what my book says, AB.
8-5-2a: It is a safety when...
A runner carries the ball from the field of play to or across his own goal
line, and it becomes dead there in his team’s possession.
EXCEPTION: When a defensive player intercepts an opponent’s forward pass; intercepts
or recovers an opponent’s fumble or backward pass;
or an R player catches or
recovers a scrimmage kick or free kick between his 5-yard line and the goal line, and
his original momentum carries him into the end zone where the ball is declared dead
in his team’s possession or it goes out of bounds in the end zone, the ball belongs
to the team in possession at the spot where the pass or fumble was inter cepted or
recovered or the kick was caught or recovered.
