• I think it would have to be B due to the laws of relative motion. It was easier for me to think about when I considered the opposite case. Imagine someone is on a vehicle, for example a boat, with one portal on the boat and the other on the shore. You wouldn’t expect someone casually walking through the portal on the boat while it’s moving to suddenly experience the momentum of the boat after exiting. This is because the person and the portal are both experiencing the same motion.

      Going back to the original scenario, the relative motion of the people entering the portal is as fast as the trolly is moving. If there was no portal, they would experience the same force if the trolly ran into them as they would if they ran into a stationary trolly at the same speed.

      You have to do funny things with the conservation of momentum when dealing with hypothetical portals because the portals allow you to abruptly change the frame of reference.

    • Well in the portal games I don’t think portals have ever moved

      But the way I see it the “distance” you travel through the portal is the same. You don’t go through a tunnel it’s instantaneous. But one portal is moving so I think just and endpoint is moving

      I’m thinking of it like a normal door

      If a run through a door I will inherit my momentum like in the portal games

      But if a door is quickly coming at me and I’m standing still the frame just goes around me I’m still

    • Momentum is transferred from the trolley to the victims. In order for energy to be conserved, when they accelerate, the trolley will slow down. Now that you think about it it’s not that different from being hit by a trolley that has no portal on it

    • Yeah, I’d be a bit more careful about making statements on physics education. The setup in itself is breaking physics itself. Arguing about what would happen is like saying “if we ignore the rules, what would happen according to the rules?”. It’s theoretical either way and there’s no correct answer.

    • Whoopsie. Maybe take another look at how portals are handled in the game. Then extrapolate that to this "conundrum "

      The answer is neither. They wouldn’t be ejected at all theyd just fall right back into the portal. Which would make them fall back through the orange back and forth forever. Until someone grabs the blue portal wall and pulls them out.

        • You’re saying that there should be such a thing as a “proper scientific conclusion” to this meme about a video game physics engine? The only definition of these portals that we have to work with is the definition in the Portal physics engine. There is no definition of anything that behaves like these portals in the scientific study of physics. It is meaningless to try to draw a scientific conclusion about something that does not have a scientific definition.

  • I was team A, but after thinking all morning I’m team B

    Imagine the exit portal is on the back of the trolley, it doesn’t even have to be a portal, even just imagine it’s an open hole in the front and back of the trolley. As it approaches you jump up, enter the front and exit the back without landing, you then land where you started. See how in this case your momentum doesn’t change because both portals are moving at the same speed. If the exit portal isn’t moving, you’ll gain that momentum.