How to sit when hit by part with a certain velocity?

I did some research about velocity parts or body but I really still don't understand, hopefully I do someday. This script I added into a part that makes the humanoid sit if they touch it, but I want it to make them sit the part is moving with a certain velocity or something?

script.Parent.Touched:Connect(function(hit) 
    if game.Players:GetPlayerFromCharacter(hit.Parent) then 
        hit.Parent.Humanoid.Sit = true
        script.Parent.Hit:Play()
    end
end)