How would I go about changing this from linear gravity?

--Particle--
wait(1)
grav_force = 5
terminal_velocity = 10
function coroy()
while wait(1) do
grav_hori = math.random(-6, 3)
end
end

local coro = coroutine.create(coroy)
coroutine.resume(coro)

local mouse = game.Players.LocalPlayer:GetMouse()
local button = script.Parent.TextButton
local l = Instance.new("Frame")
l.Size = UDim2.new(0.001, 3,0.001,3)
l.Name = "Particle"
l.BackgroundColor3 = Color3.new(242, 213, 77/255)
down = false
    m = l:clone()
button.MouseButton1Down:connect(function()
m:clone().Parent = script.Parent
m.Position = UDim2.new(0, mouse.X, 0, mouse.Y)
end)



function update()
for _,v in pairs(script.Parent:GetChildren()) do
if v.Name == "Particle" then -- Something like that
v.Position = v.Position + UDim2.new(0, 0, 0, grav_force + 1)

end
end
end

while wait(0.05) do
    update()
end

I want it so, the particle speeds up as it falls