Cframe to velocity?

Well, if you did this:

p.CFrame = p.CFrame * CFrame.new(Vector3.new(0, -4, 0))

it would immediately move it down 4 studs, but if you used velocity, it would gradually move down. I'm assuming you would prefer the latter; in that case, you would use a for loop:

for i = 1, 10 do -- Change the 10 to how much you want the part to move down.  10 will move it down 1 stud.
    p.CFrame = p.CFrame * CFrame.new(Vector3.new(0, -0.1, 0))
    wait(0.1) -- Change the 0.1 to how fast you want it to go down.
end

That way, you don't need velocity. And yes, you can check for Touched events.

p.CFrame = p.CFrame * CFrame.new(Vector3.new(0, -4, 0))

Was taken from a for loop here's the full code

for i = 1 , 150 do
        d.Transparency = d.Transparency + 0
        d.CFrame = d.CFrame * CFrame.new(Vector3.new(0, -2, 0))
        p.CFrame = p.CFrame * CFrame.new(Vector3.new(0, -4, 0))
        m.Scale = m.Scale - Vector3.new(0, 0.02, 0)
        wait()
end 

Also this script is cloned into p and it doesn't work so that's why I thought I need to change it to velocity, why won't this script work?

arrow = script.Parent
damage = 4

function onTouched(hit)


    humanoid = hit.Parent:findFirstChild("Humanoid")
    if humanoid~=nil then
        humanoid.Health = humanoid.Health - damage
        wait()
    end
    if hit.Name == "Blast" or hit.Name == "BasePlate" then
        Effect = Instance.new("Part")
        Effect.Parent = game.Workspace
        Effect.Anchored = true
        Effect.CanCollide = false
        Effect.Size = Vector3.new(1, 1, 1)
        Effect.formFactor = "Symmetric"
        Effect.Transparency = 0
        Effect.BrickColor = BrickColor.new("Institutional white")
        Effect.TopSurface = "Smooth"
        Effect.BottomSurface = "Smooth"
        EffectMesh = Instance.new("SpecialMesh")
        EffectMesh.Parent = Effect
        EffectMesh.MeshType = "Sphere"
        EffectMesh.Scale = Vector3.new(1, 1, 1)
        for i = 1 , 20 do
        Effect.CFrame = CFrame.new(hit.Position)
        EffectMesh.Scale = EffectMesh.Scale + Vector3.new(1, 1, 1)
        wait()
        end
        wait()
    end
end

arrow.Touched:connect(onTouched)