Translation:Wat is een eenheid van snelheid?
Would you say that "spoed" is different enough from "snelheid" that you don't normally speak of an "eenheid van spoed"?
Would you say that "spoed" and "snelheid" are synonyms except in a scientific context?
"Spoed" is pretty archaic and not often used, definitely not in a scientific context. It also implies, at least to my mind, there being somewhat of a hurry involved, which is not the case for "snelheid". Perhaps that is just because of the proverb: "Haastige spoed is zelden goed" (Hurrying is rarely good).
I think it might be overstating the case to say that it's archaic. Just in the last week, there have been hundreds of news articles with the word "spoed" in them. I notice that it occurs in the vast majority of cases with the sense of urgency or absence of delay, like you said:
"De brandweer kwam met spoed ter plaatse" "Omdat er spoed achter zit vindt het debat mogelijk maandag plaats." "Het bellen van 112 is bedoeld voor spoed."
In Afrikaans the words appear to me to be more closely related than in Dutch. Maybe I could improve what you said by saying that "spoed" in the sense of "snelheid" is uncommon, or not standard Dutch, or dialectal?
Fair enough, I was exaggerating. "Spoed" definitely is used. And as you say, I would rather translate it with "haste" or "urgency" than "speed". In the Dutch as I know it, it is not synonymous with "snelheid".
Sorry for the confusion, I hope that was at least slightly helpful.
I'm sorry that I forgot to thank you! Thanks!
The problem with the internet as a source for usage examples is that there's really no way to be confident that what you're reading is a standard, a trend, or a deviation (unless that's what you're reading about).
Even native speakers don't always use their language "correctly". And the users of some languages far out-number the native-speakers. So, it takes patience and some help to clear the fog before I can see clearly what is clear and what is foggy.
You were very helfpul. Here are some Lingots to make up for my rude ingratitude, earlier.