llGetMass
LSLfloat llGetMass()
Returns the mass of object that the script is attached to.\ Returns the scripted object's mass. When called from a script in a link-set, the parent will return the sum of the link-set weights, while a child will return just its own mass. When called from a script inside an attachment, this function will return the mass of the avatar it's attached to, not its own.
Takes no parameters.
The Linden Scripting Library — what every SL-compatible grid provides.