Short and sweet of what I’m thinking. Imagine you jump out of an air plane and reach terminal velocity. Now imagine you were flying down and hit a portal that reversed the direction you were falling just before you hit the ground. *see diagaram*

portal example

What would happen to you? would you fly straight up at the same speed (almost like jumping) and return to the ground moments after? or would the reversal of gravity smash you like a pancake?! like hitting a wall of gravity.Almost like when 2 cars hit head on, one is going 30 miles an hour and the other is going 35. the combination is similar to hitting a parked car at 65 miles an hour.