Except in that scenario both portals are moving if they act like a moving hole. Imagine a hula hoop, except it's 2 portals connected back to back. If I passed a hula hoop over you, you'd be going into the bottom at the same velocity that you are coming out the top, therefore momentum is preserved. You're moving at the exact same velocity in reference to both of the portals
a portal is supposed to be like a hole that you go thru except you end up somewhere else, if i pass a hole over you, would you feel anything? A
Except in that scenario both portals are moving if they act like a moving hole. Imagine a hula hoop, except it's 2 portals connected back to back. If I passed a hula hoop over you, you'd be going into the bottom at the same velocity that you are coming out the top, therefore momentum is preserved. You're moving at the exact same velocity in reference to both of the portals