Contractions in odd Places [duplicate]

I understand contractions as just a means of merging two words into one, with some added punctuation, but there's some cases where I feel I'm grammatically correct, but using them incorrectly.

For example, "Have you ever been to the market downtown? I know I've."

Or, "Will you guys be coming with us?" ... "Yes we'll."

And, "If that won't work, what'll?"

Is there some grammar rule against doing this? Is there a reason why this isn't common? What makes doing this feel awkward?

Solution 1:

You cannot end a sentence with a pronoun-verb contraction.

From LiveMocha:

...you CANNOT end a sentence with contraction if it is a Type 1 (Pronoun-Verb). Not in formal English, not in informal English – never! In this case, you must write out the entire verb that follows the pronoun. So take a look at the contraction at the end of your sentence. Does it contain a pronoun? If it does, then break it up into its two original words.

From English expert Eugene Mohr:

[In written English,] No contraction takes place if the form of be, will, or have occupies the final position.

You may also be interested in the following discussions/posts:

Is there some rule against ending a sentence with the contraction “it's”?

Ending a sentence with a contraction

Yes, I'm.

Why does it sound so weird to end a sentence with a contraction?