this post was submitted on 18 Aug 2023
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[–] Declamatie@mander.xyz 5 points 1 year ago

C. A train flies out of the blue portal

[–] SecretPancake@feddit.de 5 points 1 year ago* (last edited 1 year ago) (2 children)

I don’t think portals carry the momentum with them. It’s as if the train is a moving tunnel. So A.

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A if the trolley is going slow

B if the trolley is going fast.

This comment section reminds me a bit of these cringe powerscalers, discussing Saitama vs Son Goku in the comments of a YouTube video.

[–] ABC123itsEASY@lemmy.world 4 points 1 year ago

If it's A, then it figures to me that the blue portal would enact some force on the structure on which it's placed when the tied up people plop out

[–] tiredofsametab@kbin.social 4 points 1 year ago

B, but only their bellies; the portal is above most of their bodies, and their heads and ankles will get cut off for being off even the track.

[–] UnhealthyPersona@beehaw.org 3 points 1 year ago (4 children)

I've seen this debate about the outcome of the moving portal. I'm pretty certain that because of inertia, and the people aren't moving, they will just plop out the other side. Think of it like moving a hoola hoop through the people. That's basically what the portal is.

The hoola hoop has inertia and is moving, but it doesn't actually come in contact with the people, so it passes right around them. There's no way for the people to have instant acceleration because the porta did, otherwise it'd be like them hitting a brick wall and they would probably explode

[–] towerful@programming.dev 5 points 1 year ago

Momentum is relative.
If you say the portal is stationary, and the person is moving then B makes sense. However, this is just changing the frame of reference from following the tram to following the person.
Changing the frame of reference (from tram to person, or from person to tram) doesn't change the velocity/momentum/energy (it's just the person is moving towards the tram or the tram is moving towards the person).

The acceleration the person would experience is likely similar to if the person just gets hit by the tram, however in Portals canon it is nonexistent.
Because, as you say, the person is accelerated. However, the acceleration when using the tram as the frame of reference is still 0 when you account for the rules of physics a portal would break. Even changing the direction of travel would be acceleration.
Like, if the in-portal and the out-portal were back-to-back where there was absolutely 0 distance between them, anything passing through the portal would experience 0 acceleration - no change in direction, it might as well be a standard hoola-hoop.
If the portals were side-by-side facing the same direction, anything passing through the portal would experience twice the acceleration of running into a wall - like bouncing a ball off a wall. Once going into the portal (forward motion) and once coming back (backwards motion), because the object has to completely reverse it's velocity.

And considering that things going into portals do not get damaged (and chel doesn't lose health) it's fair to consider that objects observe 0 acceleration.

But portals moving is outside of the Portals canon because it highlights that an object experiences acceleration when passing through a portal. And the acceleration is (or is near) instantaneous. And the object does not suffer from this.

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