From SRD
Whip: The whip deals sub dual damage. It deals no damage to any creature with even a +1 armor bonus or at least a +3 natural armor bonus. Although the whip is kept in hand, treat it as a projectile weapon with a maximum range of 15 feet and no range penalties.
Because the whip can wrap around an enemy's leg or other limb, trip attacks can be made with it. If a character is tripped during the trip attempt, the whip can be dropped to avoid being tripped.
When using a whip, add a +2 bonus on the opposed attack roll when attempting to disarm an opponent (including the roll to keep from being disarmed if the character fails to disarm the opponent).
Disarm(4) [Varies][AoO: Yes]
Description: The combatant and an adjacent target make opposed attack rolls with the their respective weapons. If the weapons are different sizes, the opponent with the larger weapon gets a bonus on the attack roll of +4 per difference in size category. If the target is using a weapon in two hands, he gets an additional +4 bonus. If the combatant beats the target, the target is disarmed. If a combatant attempted the disarm action unarmed, the combatant now has the weapon. Otherwise, it drops to the ground at the target's feet. If the combatant fails, then the target may make an attempt to disarm the combatant as an immediate, free action.
Note: A target wearing spiked gauntlets can't be relieved of the gauntlets by a disarm action. A target using a weapon attached to a locked gauntlet gets a +10 bonus to any disarm attempt made by an opponent.
This action substitutes for a melee attack, not an action. As melee attacks, it can be used once in an attack or charge action, one or more times in a full attack action, or even as an attack of opportunity.
Trip an opponent [Varies][AoO: No]
A combatant can try to trip an opponent as a melee attack. A combatant can only trip an opponent who is one size category larger than a combatant, the same size, or smaller.
Making a Trip Attack: Make a melee attack as a melee touch attack. If the attack succeeds, make a Strength check opposed by the defender's Dexterity or Strength check (whichever ability score has the higher modifier). A combatant gets a +4 bonus for every size category he is larger than Medium-size or a -4 penalty for every size category he is smaller. The defender gets a +4 stability bonus on his check if he has more than two legs or is otherwise more stable than a normal humanoid. If a combatant win, a combatant trip the defender. If a combatant lose, the defender may immediately react and make a Strength check opposed by a combatant's Dexterity or Strength check to try to trip a combatant.
A tripped combatant is prone. Standing up from prone is a move-equivalent action.
A combatant may make a trip attack against a mounted opponent. The defender may use his Ride skill in place of his Dexterity or Strength check. If a combatant succeed, a combatant pull the rider from his mount.
This attack form substitutes for a melee attack, not an action. As a melee attack, it can be used once in an attack or charge action, one or more times in a full attack action, or even as an attack of opportunity.
