Elastic Collisions (Oblique Impact)

1. Feb 11, 2012

FeDeX_LaTeX

http://desmond.imageshack.us/Himg843/scaled.php?server=843&filename=23518417.jpg&res=medium [Broken]

The crucial thing I'm not understanding here is how they know that after the collision (shown at the bottom of the picture), the horizontal velocities of each particle are reversed. Surely we don't know that, though? However, the direction after is important because I'm getting a different answer if I just try to get v or w by itself. When I draw my diagram for what happens post-impact, I'm not giving v and w a direction, I'm just labelling them as horizontal components. However, to solve this question I think you need to know which direction they're in.

Any help?

EDIT: Sorry about image quality. Co-eff of restitution is 3/4.

Last edited by a moderator: May 5, 2017
2. Feb 11, 2012

FeDeX_LaTeX

Eh, never mind, sorry. I was being an idiot, of course it shouldn't matter. I was doing Newton's Law of Restitution the wrong way round...