# Conservation of Linear Momentum with respect to a given direction

Is linear momentum conserved in any direction? More specifically, if you project all momentum vectors in a system onto another vector, will momentum be conserved?

I know that momentum is conserved along the $x$ and $y$ axes, so I'm expecting this to be true, but I have yet to see a rigorous proof.

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Comment to the question(v1): Are you considering an isolated system? – Qmechanic Oct 31 '12 at 21:53
yes, it is an isolated system – Ben Oct 31 '12 at 23:04