Propulsion that does not involve driving wheels

[EricH]

Comphappy, I see where we really differ, now that you have explained where you and I differ. What you call "u" (the coefficient of friction) is normally hand-written as "μ", which is the Greek letter "mu". I used "mu" to designate this letter, while you use "u". I then used a "*" to designate multiplication.

I have edited my last post to reflect hand-written usage. Please go through again and tell me if I am still wrong.

As for why metric matters, I am simply much more familiar with the mass/weight units in metric. I couldn't even tell you what the units for slugs (the English system version of kilograms) are.