Help- Physics Momentum Lab Sources of Error

[TaintedLove]

Hi Everyone! I'm a grade 12 physics student and we conducted a momentum lab. On a frictionless surface, we conducted a simple 2D collision and using the data gathered from that, we had to calculated the momemtums and indicate what type of collision had taken place... that was all fine and done but now I'm having difficulty thinking of possible sources of error? Could someone please help me out. Below I'll post a picture of the apparatus.

 

[Stonebridge]

It depends on what measurements you took, and the equipment you used to do it.
Could you give a little more information?
For a start: do you know the precision (scale sensitivity) of the instruments?

 

[TaintedLove]

Well, it was a glass tube, covered with a garbage can and the system was set up in such a way, that when it was turned on, it was supposed to be frictionless. We collided the two masses and used a stop watch to find out the time.