As always, context is the key to knowing what you should say.
In general, it is better and more natural to use the present perfect tense if you are asking somebody whether they have (recently) completed a piece of work.
For example, if you are the boss of a company and have hired somebody to do a particular piece of work, you would ring them up and say:
"Have you finished the work, yet?"
You could say "Did you finish the work yet?" but that's less natural.
You could also ring him up and say "Is the work finished now?"
In this situation you shouldn't use the simple past tense of the verb "to be," unless you are going to put in a word that specifically refers to the past: So you should not say "Was the work finished?" without referring to a period of time that is in the past - for example "yesterday, last week etc"
So you could say "Was the work finished yesterday?" but it would be more natural to say "Did you finish the work yesterday?"
Note: in all of the uses above, it would be far more common to say "the work," rather than "your work."