5 points

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.

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21 points

Gotta be B, right? But then if the victims had no momentum… ah this hurts my brain

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12 points

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

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7 points

Yeah but I don’t think the portals can distinguish relative speed, and so it would just see you moving through the portal at 60 mph or whatever and shoot you out at 60 mph at the same angle relative to the portal.

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11 points

But if the door is coming at you fast, isn’t the ‘room’ too?

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6 points

Yes but

AAAAAAAAAAAAA

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6 points

There is ONE case of portals moving and it was specially coded because you’re right that they usually don’t.

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5 points

Momentum is relative. Whether the victims move to the trolley or the trolley to the victims doesn’t make any difference.

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19 points
*

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.

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5 points

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

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11 points

It’s A. Object momentum is the only part that matters to portals, so they would just plop down.

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1 point

Think about how fast the people will be moving through the portal, their matter will be shoved through extremely quickly so it wouldn’t be right for them to suddenly lose that momentum when they’re all the way through.

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7 points

Motion is relative, there is no sationary reference frame. From the reference frame of the portals, they do have momentum going towards the portal

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3 points

Since their heads and feet would be outside of the portal, neither of the choices are correct, because in both choices they are uninjured at the pictured time.

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5 points

B, final answer. Who tests this?

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