Well the federal gas tax is 18.4 cents per gallon, and the state gas tax where I am is 28.5 cents per gallon, for a total of 46.9 cents per gallon, that’s where the $0.009 comes from.

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