Relative to the train, and by extension the portal, the people are moving towards it at the same speed as the train relative to the ground, since the people are tied to the ground. I’m gonna work with the definition of momentum that equals it to the velocity of an object times its mass, and with the assumption that the portals conserve mass and momentum of the objects during teleportation, or with negligible losses. Having found that the momentum stays constant, and given the mass before and after teleportation is constant, the velocities relative to the portal are gonna be constant too. (p1=p2 <=> mv1=mv2 <=> v1=v2). And since the velocity of the people relative to the portal is the velocity is the train relative to the ground, and the velocity of the train relative to the ground is far bigger than the velocity of the people relative to the ground, the answer is gonna be B, where the people shoot out of the portal with great speed.
If the people actually go into the portal and not under it that is.
If that is so, the train or portal would have to lose its momentum for the transfer to happen otherwise you’d be generating more relative velocity after the portal. I can’t imagine portals transfering monentum, only maintain it.
Think of it as a pole entering the portal, the end will have to exit at high speeds and so it will need to drag the rest of it out at that speed
That might be the crux of it.
If you replaced the people with a pole on a roller, you wouldn’t expect the pole to get sucked into the portal or to roll towards the tram as it advanced, right?
That is what would happen if people were launched out of the other side of portal. The part of the pole that has been launched would drag the remainder of the pole with it.
But that wouldn’t happen.
The pole would just lay there until the tram passed it by, so the answer must be A. There’s no momentum added to the pole as the tram passes it by. The only thing that changed is the location of the pole.
