promisary notes

I live in utah

my wife signed without my knowledge a hand writen
document unnoterized to pay her mother a certain
amount of money that she thinks I owe her, and stated
that if she(my wife) did not pay this amount every month
she(my mother in law) would have her lawyer get/serve
or whatever a promisary note to force us to pay her
does this(hand writen document) have any teeth to it or is she just trying to scare us into getting her money back

what is a promisary note?
can I be forced to sign a promisary note

If your wife signed a 'promissory note' (written promise to pay), it is a contract. And if she breaches that contract, the creditor can pursue this through the courts and very probably obtain a judgment. With a judgment, the creditor can enforce it through seizure, etc. as provided by your state laws.

And, no, you cannot be forced to sign a promissory note (unless under court order with the threat of contempt for failure to sign).