Your question:
Is impeding an opponent treated differently if physical contact is made?
My answer (July 1, 1998):
The only difference is in the way the game is restarted. Here are some examples: If a defending player physically obstructs a player of the attacking team by interposing his body between the ball and the attacker without remaining within playing distance of the ball, that is impeding an opponent, which is punished by the award of an indirect free kick to the attacker's team. If there is physical contact resulting solely from the momentum of the attacker who was obstructed, that is still impeding on the part of the defender, and an indirect free kick is awarded to the attackers. On the other hand, if the physical contact is initiated or caused solely by the action of the defending player, then the infringement has been raised to the level of holding and the correct restart is a direct free kick from the spot of the foul (or a penalty kick, if the foul occurred in the penalty area).
If the physical contact was a willful act by the attacker, rather than by the defender, the referee must deal with both infringements appropriately.
If any act of physical impediment denies a player an obvious goalscoring opportunity, then the player who committed the infringement must be sent off for denying the opposing team an obvious goalscoring opportunity and the game will be restarted according to the nature of the foul.