Grenades and rockets, like other projectiles, have entries in the physics model under
shots. The physics model assigns a base damage and random damage for each type of shot. The damage done by a given shot is a random number between [base damage] and [base damage + random damage]. This damage is applied so long as a monster is within the shot's area of effect, which is another stat in the physics model. That means Aleph One doesn't calculate a falloff - the damage is all or nothing.
Monsters, including players, have an external velocity scale which affects how their velocity is affected by shots. Here's a quote about the external velocity setting from Mark Levin's physics model reference.
This is the factor by which damage from a projectile is transferred into the monster's motion. A factor of 1 means full transfer, .5 means half transfer, 0 means immovable, etc. Note that projectile damage is on the same scale as monster speed, so a monster that takes 50 damage with an EVS of 1 will start moving at 50. Also note that the player's EVS is kept in his Monster record and not Physics. also note that not all damage types have the same "punch factor", which seems to have the same behavior as EVS but is stored in the MI app and are apparently uneditable [HAS] One final note: Marathon seems to add damage seperately as magnitude and direction, not as true vector math. Also monsters don't decelerate (significantly) until they hit the ground. This means that a monster that gets blasted into the air and then takes several hits in a row from different directions will end up being flung in the direction of the last hit at a truly incredible speed. I've thrown monsters several dozen yards at least, and once when I tore up a Mother of All Cyborgs with rapid rockets I had him jammed in a corner, against the cieling, for at least a minute.