could you describe your prac?
sources of errors could include inaccurate timing, not enough decimal places in calculations, parallax error, inconsistent method, the list goes on.....
the conclusion is where you've analysed your results, and you write how these results correlate to prove something. Or the conclusion could even be that you could not detect a relationship.
But tell us some details about your prac and youll be able to get some specific answers from people