HOW DO I REMOVE THE BOUNCE WHEN AN UNACHORED PART FALLS AND HITS A SURFECE?

You need to add a script into the part then put this into it.

local part = script.Parent

local friction = -10000
local elasticity = -1000000
local frictionWeight = -1000


-- Construct new PhysicalProperties and set
local physProperties = PhysicalProperties.new(friction, elasticity, frictionWeight)
part.CustomPhysicalProperties = physProperties

Hopes this help

This is the dev fourm link. https://developer.roblox.com/en-us/api-reference/property/BasePart/CustomPhysicalProperties