Dynamics: Collision with inclined plane

[MechEngrStdnt]

Homework Statement

I have two conceptual questions that I have written in read in my solution. The solution, and all the work, is correct. However there are two things that I am unsure as to why I am doing it. Thanks!

Homework Equations

Included in solution, although none should be needed as questions are conceptual.

The Attempt at a Solution

The attachment is well under the limit, I don't know why the quality is be lowered so drastically...

 

[BvU]

Can read the momentum question. With difficulty.
Momentum isn't conserved because the plane exercises a force. Since it is smooth, it can only exercise a force perpendicular to its surface. Along the incline no force, so momentum conservation. Can't distinguish what your x, y, directions are. Make a better picture or type it out.