tackling rules?
 

when is a player down by contact, for example, if the ball carrier is touched and maintains his balance and then a few steps later falls is he down? obviously if he is touched by a defender and then falls he is down but after what amount of time is he not down. say he goes through the line and is touched by 3 players then 20 yards down the field he falls, obviously he is not down

hopefully someone can understand what i mean

This is obvioulsy an NFL rules question, judgement must be used in this case. If the contact caused the player to go to the ground then he is down. If he is touched by 3 players, then 20 yards later he falls down, it is unlikely that it was caused by the players, therefore he could get up and continue downfield.`