"Yes, mom is there."
Translation:Так, мама там.
Disclaimer, have only been learning Ukrainian for almost a fortnight :-o so take what I say with a pinch of salt (though I already spoke Russian which is closely related), BUT Ukrainian, like Russian (and Turkish and Hebrew and probably other languages!), usually omits "to be" in the present tense, when it's the copula (the sky is blue, mum is here, I am English). In this phrase, when you say "мама там", the "is" is understood.
(Ukrainian actually uses є more than Russian uses the equivalent as far as I can tell, but anyway, the simple answer is that you don't need to use it.)
ETA: This is about Russian and the rules (as far as I can tell) are not exactly the same, but they are similar enough to give you an overview of how East Slavic languages deal with the copula in the present tense http://en.wikipedia.org/wiki/Zero_copula#Russian