I suggest you use BodyVelocity instead, but if you still want to just use BodyForce then here,
function calculateForce(Direction,Speed,Mass)
local Force = (Mass*workspace.Gravity)+Speed
return Direction*Force
end
this function will give you the force needed to move an object using BodyForce or VectorForce
you can use it like this
local Ball = script.Parent
local BodyForce = Ball.Force
local Speed = 50
local Force = calculateForce(Ball.CFrame.LookVector,50,Ball:GetMass())
BodyForce.Force = Force