One of my textbooks explains it this way:
ZNÁT -- to know, be acquainted with, be familiar with
VĚDĚT -- to know about, be aware of, be informed about
Helpful hints on when to use which verb (from the author of the textbook):
ZNÁT -- always takes a direct object
VĚDĚT -- usually followed by a clause
My own additional thinking on this:
"Vědět" also SEEMS to be used in the sense of "knowing" in general, that is, when there is neither a direct object nor a clause that follows it... just as in the sentence in this exercise.
No, you would need to use "znát" in such case. "Koho zná?" See BHB's post above.
This might sound like a dumb question, but, why is "ví" being used as "knows" rather than "znát" or "vědět"? Thanks
Because we have no object or subordinate clause I can only say because that is how we say it.
It may be helpful to consider the difference between these verbs in other languages as Czech is the typical language here and English is the exception with mixing both. German: wissen/kennen, French: savoir/connaître, Italian: sapere/conoscere. I do not know French or Italian, but in German it is "Wer wisst?" similar to Czech.
Why does the following conjugation of vědět, not contain ví? http://www.verbix.com/webverbix/go.php?D1=205=vědět. Is it a mistake or something more sinister? ;)