Conservation of momentum in perfect elastic collisions

[anachin6000]

I learned that momentum conservation is vectorial, and now, when i read about perfect elastic collisions, I can't understand why they use a scalar conservation. I tryed to use vectorial coervation to see the diference and it's true: it's needed a scalar conservation. But why?

 

[olivermsun]

Momentum is a vector and is always conserved, whether the collision is elastic, inelastic, somewhere in-between.
Energy is a scalar and is conserved only in an elastic collision.