I am having a problem coming up with an empirical formula for multiple objects moving with the same speed relative to each one up. I.e. there is a cart moving with speed u relative to me, and inside it is a cart moving speed u relative to the cart is inside it. and inside that cart is a cart moving speed u relative to the second cart. and so on... what i can't seem to come up with is an empirical formula that gives me the speed of the nth cart relative to me. so far i understand that if i used the tanh(λ) formula to derive an empirical formula because it just seems to get bigger for each additional cart.