After setting foot on the Moon, the next destination for humankind is Mars, which presents a whole new set of challenges in speedy, long-distance space travel.
After setting foot on the Moon, the next destination for humankind is Mars, which presents a whole new set of challenges in speedy, long-distance space travel.
Hey, no need to be sorry. I appreciate the search for correctness and especially the reference document.
Here’s what I’ve found.
There is no mention of
km/h
in section 4, “Non-SI units that are accepted for use with the SI”. It does mentionh
, making it a “non-SI unit that’s accepted for use with the SI.”km/h
is its own unit separate fromh
. It’s a unit of speed, derived fromkm
andh
.My gut feel at this point is that
km/h
could be an SI unit since it’s a unit of speed derived from an SI unit for distance and a non-SI unit accepted for use with the SI for time.Furthermore, searching the document for mentions of
km/h
, there’s this bit on page 127, section 2.1, “Defining the unit of a quantity”:This paragraph suggests (even though it doesn’t outright say it) that
km/h
is indeed an SI unit.I haven’t found anything clearly saying whether
km/h
is an SI unit or not. Not on that document, not by searching the web. The research above makes me lean towards the idea that it is one.If you found otherwise, I’d love to compare notes and learn further.