You should also show you code to know what you have done.
Otherwise I have to assume you do not know how to account this additional vector force within the ball.
For that you should decrease the gravity according to the acceleration caused by the vector force like so:
--F = ma, Newton second law
-- F/m = a, F = vector force N, m = mass, a = acceleration
local g = Vector3.new(0, game.Workspace.Gravity - 270/ball.AssemblyMass, 0)
local function x(t, v0, x0)
return 0.5*g*t*t + v0*t + x0
end