Imperatives

[aysaa]

Hello,

-Study your homework or not (don't) , it is your problem.
-Send me a post card or not (don't).
-Go or not (don't).

I can't figure out which one is grammatically OK in these sentences, is it with not or don't?

Thanks.

[Grumpy]

In the case of these imperatives, "not" is not appropriate, but "don't" is insufficient on its own. I would express these as:

Study your homework, or don't study your homework [or don't bother]; it is your problem.
Send me a post card, or don't bother.
Go, or don't go.