Overeride / limit velocity of a sprite/node

Hello, I want to make objects fall only vertically. I do not want any sideways impacting/velocity/movement at all.
Currently i am using the physics thats build into cocos2dx 3.3.

I would like to limit the velocity to only up and down/ vertical ?

Any ideas?

  1. Hack the engine and overwrite velocity? I so far cannot find where velocity is even applied.
  2. Stop using chipmunk and write a very basic physics as i only want things to fall. However i hoped to use chipmunk for collisions and bounding.

similar to this: http://chipmunk-physics.net/forum/viewtopic.php?t=1607