"Velocity is relative" doesn't really apply here. The question is momentum, the pedestrians have none, the portal will pass right around them. Imagine the exit portal is on the back of the train, it would be as if a large hollow tube was passing around the pedestrians, they would still be laying there stationary.
"Velocity is relative" doesn't really apply here. The question is momentum, the pedestrians have none, the portal will pass right around them. Imagine the exit portal is on the back of the train, it would be as if a large hollow tube was passing around the pedestrians, they would still be laying there stationary.
Momentum is relative too, since it's equal to mass times velocity (in classical mechanics, of course)