>>9063362

Or would it?

If you enter an orange portal and exit a blue portal, your motion relative to the orange portal is transformed (upon exit from the blue portal) into motion relative to the blue portal.

For stationary portals, this means that you conserve the magnitude of momentum, while changing its direction. For moving portals, the movement relative to the orange portal becomes movement relative to the blue, so the answer is B.

Depends on the amount of force applied to the panel with the portal.

What about if you invent those portals first and then you come back to ask us what would happen.

portals are destroyed on moving surfaces (the neurotoxin puzzle doesn't count, since that was the one time they were programmed not to)

That's because the upper part of the cardboard (the exit hole) is also moving down relative to the wall, retard.

A. The block itself has no momentum.

Objectively the dumbest responses these threads get (including "muh hoola hoop") and yet some retard always feels the need to remind us that portals don't exist anyway.

>every hole has two holes. An exit hole and a entrance hole.
Sounds like your mom

Fucking brainlets that never played the game, I swear to god

>Knowing it's a videogame

>forgetting the moon or, on that point, the earth and the objects on it moving

of course it doesn't, you stopped the cardboard's movement relative to the cube. if you continued to move the cardboard, the cube would indeed "shoot out" of the hole in it. the problem with portals, though, is that you can move one portal without moving the other.

Portals can not be placed on moving surfaces.
>MUH MUH PORTAL 2
at that point they were pulling shit out o thin air to make the game enjoyable to the masses you dumb shits.

Motion is relative, so a portal moving quickly to the cube is the same as the cube moving quickly to the portal. It's B.

But the portal wouldn't stop when it hits the surface holding the cube. It would be as though it kept on going, the cube moving further away from the hole, which is show in B.

Exactly. The portal is moving at some velocity, but the portal has 0 mass (its a hole). Unless the block is also massless, it will just plop out of the other side.

Momentum is conserved.

actually, to the orange portal, the cube has momentum, since it's moving.

You can test that. Drop a hoola hoop around a block and if the block flies up, its B.

okay, find me a hoola hoop that has sides that can move independently from each other like portals.

Lets say a photon is travelling towards the portal and the portal is travelling towards the photon at 0.99c. What happens to the photon exiting the blue portal if B is correct?

the photon will move at c, since that's how fast photons move.

I'm so sick of this misunderstanding. The blue portal is moving the same speed relative to the orange as it is relative to the cube. The block and the orange portal are in the same frame. Therefore, the block is not moving relative to the orange.

The rebound effect will be locked in a 360* portal hole.
This will cause the material below to vibrate and if sufficient pressure is available as the press smashes down it will cause the block to "Hop" a little. However because the block is not moving the block will slide down the rest of the way.
However

What? If the block is not moving then how the hell is it going through the portal?

If you slammed said portal onto your girlfriend's penis would it become a real woman?

Depends how hard I can smack it without breaking my hand...

that game is cancer

portals must:
1) be stationary relative to one another
2) be oriented spatially in the same direction

if these two rules are violated then they don't work.

A, the block has no momentum. Actually, it would probably look like it's halfway in the portal, if we're going by game logic, since all the portals are like an inch thick.

I meant blue, not orange. Sorry.

To be honest, that doesn't really change anything - the cube still has to move through it.

My argument is the only thing that matters is the cube velocity relative to the exit. In this case it is 0, so a is the answer.

but it's not 0, it's moving out of it

This

Not one (1) reply stating the correct answer of B.
Instead:
-Autistic faggots arguing that 'It's just a game the answer is meaningless GOTCHA'
-Portals are the same as holes in a piece of cardboard (???)
-some retarded shit about how block A 'has no momentum and therefore A for some reason'. Honestly whoever is arguing this garbage just needs to neck themselves

A.
The cube has no momentum or velocity.
Imagine it like a door fired towards you, it stops as you pass through the doorway but you weren't moving so you dont go anywhere.

>The cube [has no velocity]
Almost had it there, brainlet.

The cube has velocity relative to the portal moving towards it
>B-but that doesn't count
Learn some basic fucking relativity.
Stay underage Veeky Forums

>favoring one frame of reference over another equally valid frame of reference instead of becoming aware of the fact that neither answer is correct because the entrance portal, if portals existed, cant move relative to the exit portal.

>physically impossible
>tfw ywn have a portal to the inside of user's onaho to suck and fuck

okay listen up brainlets

there are two frames of reference here.
[1] the frame of the cube at rest
[2] the frame of the cube exiting the blue portal

If we examine the cube appearing in [2], then the cube's matter will be exiting on a straight path at the same rate as it enters the orange portal. That's literally just the definition of velocity.

>ignoring the other equally valid frame of reference for literally no good reason.

Fine. Information can flow from [2] to [1] and vice-versa. The particles in frame [2] tug across the portal boundary and the cube in frame [1] picks up momentum. Now the cube in frame [2] receives information from the cube in frame[1] and speeds up accordingly. This feedback effect occurs continuously and at the speed of light until the internal friction from the momentum exchange heats the cube up to temperatures sufficient for it to melt and no longer be bound to itself in the other reference frame. It deforms into a ten-foot long cylinder of molten steel before cooling from the sudden expansion. With an earth-shattering explosion the rod is launched through the roof of quirky underground science base #5 at hundreds of m/s to sail across the globe and penetrate your awaiting asshole. no lub.

...

...

Does this make a difference to anyone but me?

It is A but if the orange portal didn't stop moving then it would be B

It doesn't change the answer, you just hope it helps the brainlets see.

At the end of portal 2, you end up placing a portal on the moon (with an orbital velocity of about a kilometre a second) and a couple of personality cores get ejected into space. Seeing as, when they leave the portal, the debris, whilst fast moving, does not have any real sideways velocity to speak of relative to the lunar portal (which would be necessary to conserve momentum in any normal frame) and, even ignoring the components, is not moving anywhere near a kilometre a second, I believe that the interpretation that momentum is the same going into the entrance as leaving the exit (in their respective frames) is the correct one. So B.

Consider when there is only 1 cm of cube not through the portal yet. That means the rest of the cube is coming out of the other portal at 10 m/s in order to make room for the rest of the cube. It requires strange additional assumptions to make it just spontaneously lose this velocity and simply drop.

So if the answer B, does that mean if i slammed a portal onto my dick it would get ripped off?

youtube.com/watch?v=S85nudR6D-Y

Definitive answer. The cube glitches into the floor.

Posting anime girls online even though you're a 23 year old man.

That depends on how hard you can slam.

If you imagine the cube floating in a vacuum and the orange portal continuing after passing the cube, then you will see that it is actually B which allows the cube to remain motionless from the perspective in which it is motionless, whereas in A it would be dragged along by nothing.

A.In order to conserve the momentum, it can be seen as a stationary cube and the universe moving in opposite direction so for observers look like is coming out but with no momentum.

It can simultaneously be seen as a stationary universe with the cube moving into it.

Portals appear to conserve momentum in reference to the portal in the game.

B is the only possible answer. The portal has no way of knowing whether it is 'stationary' and the block is moving, or vice versa. And by all accounts, it conserves the magnitude of the incoming object's momentum, while changing the direction and position in space. So it has to conserve it with respect to itself, and not some arbitrary external observer.

The block has a momentum of its mass times its velocity relative to the portal. Or do you suppose that the walls it gets projected on in the game are somehow totally immobile in some absolute frame of reference?

And why would the portal conserve the block's velocity relative to you, the external observer, rather than itself?

Both to itself and to an external observer the block has two relative velocities.

And why does the observer's matter? There can be an arbitrary number of observers moving at arbitrary velocities. Which does the portal prefer? The only answer that makes any consistent reasoning possible is that it does its own. If the block was going 20m/s into the portal, it's gonna fly out at 20m/s on the other side. Regardless if you, the observer, are also moving 20m/s relative to the portal and thus perceive the object to be stationary. As someone said before, when the block is still coming out the other side, it's moving, right? So why should it instantly stop after it's done? The very act of moving through the portal requires the portal to conserve the object's momentum in the reference frame of the portal.

if you don't want to cause paradoxes then the only way portals work is if they are stationary relative to each other. That way all possible observers agree on the observed events.

But paradoxes are fun.

That's not actually necessary for the observed conditions in the game to be true, which is that shit can go through portals. I mean, having portals already violates every law of conservation there is. We're just discussing the mechanics of the portals we're given.

You can have one observer observe everything, though. He can see the cube both stationary and moving through the portal. The only way he can agree with himself is if both are true.

>lighten up its just a video game
then this isn't really a good topic for /sci
maybe try /v

a portal entrance and exit moving relative to one another creates a paradoxical change in momentum and violates conservation of energy.

the whole question is a brainlet tester to see who can realize its a trick question.

No reason that both needing to be stationary needs to be a problem. If they're both stationary, then it'll be B. Imagine that the orange portal is in a fixed position in space the same way a pullup bar is. You try to pull it down, but instead pull yourself up. The lever in the picture tries to push the portal down, but ends up pushing the universe up. Problem solved, as long as the portals are into alternate universes.

Not all paradoxes are false, you know.

In reality (or I suppose "reality"), there is no change in momentum. B works precisely because the cube maintains its momentum.

>B works precisely because the cube maintains its momentum

the cube has no momentum before the portal hits it, and afterwards (in B) the cube has momentum. momentum is not conserved under case B. And under case A the cube emerges at a velocity, i.e. has momentum, but then stops, again violating conservation of momentum because momentum is inexplicably lost.

both A and B are invalid and that's why the question is a brainlet detector because the only correct answer is to realize neither answer is possible.

>the cube has no momentum before the portal hits it
False. It is moving into the universe at great speed.

There is no reason the cube would gain momentum since it never interacts with anything other than the portal

Portals impart momentum. Imagine the opposite. You're stepping through a stationary portal out of a portal moving at the speed of a train. It would be as if you actually stepped out of a train.

what if the train was reversing then? Would you fly back into the portal?

Could be because of wind resistance. I think you'd just get run over.

...

Bottom situation would be V1-V2, as you and the train are going in opposite directions.

im defining the trains first movement as positive, so v2 is actually a negative number

Reasons for A:
Conservation of momentum and energy in the given reference of frame

Reasons for B:
v - V = v’ argument:
The cube has the velocity we ascribe to the portal if we look at the model from the portal’s frame of reference.
This suggests that the cube has kinetic energy, which means it must conserve that according to the portal.
As the cube’s mass doesn’t change in - or exiting - the portal (I hope) its relativistic speed must be similar to the relativistic speed before entering the portal, thus it appears to be flying away from the portal.

Collapsible corridor argument:
If you chuck a collapsible corridor at a floating kid (so that the kid goes through the collapsible corridor) it will appear as though the kid is flying away from the corridor, despite the opposite being true.

Any other arguments?

>Reasons for A:
>Conservation of momentum and energy in the given reference of frame
There are two reference frames. You can't just pick one you like. You have to account for both. In fact, B accounts for the conservation of the cube's momentum whereas A has it completely disappear immediately upon completely exiting the portal.

>relativistic speed
That's approaching light speed innit? I think you mean relative speed.

I think it helps if you imagine that each portal is a doorway into another reality with its own separate physics. We know it's the same reality, but portals don't behave that way. Just like you can have completely different gravity on the other side of a portal which doesn't affect anything outside the portal, so you can also move something relative to the person outside the portal without moving it within the system inside the portal. As long as the cube remains in the same system, it's going to behave according to those physics. But when it crosses over, it becomes subject to the rules of the other system, in which it was moving. Everything on the other side of the portal is forgotten. It might as well be a cube disappearing into a portal forever and another identical cube simultaneously shooting out of another portal. They are the same event, but they behave as if they are separate events.

>B accounts for the conservation of the cube's momentum
So, does A, because to an inertial observer the cube has no speed, and as such it has no momentum.

>You can't just pick one you like
You're right, in this scenario you should be picking the inertial frame of reference, as opposed to the non-inertial frame of reference, as it's more true to what's actually happening.

>I think you mean relative speed.
Yeah, sorry.

If scenario X and scenario Y are correct then the answer is obviously B.

If scenario X and scenario Y are not correct then please explain to me how they are not correct because I don't understand how the answer could be A.

I think you just answered your own question there. The whole idea of portals is bullshit and can't be applied to real world physics, because its not real world physics. It's made up to make the game more fun.

But what would happen if they were real?

Here's an idea, aside from the moon there was one part of the game where you could put a portal on a moving object - where you're cutting the pipes of the neurotoxin tank, but it's in a part where you don't have access to any movable props.
someone should go into that map in gmod or something and throw something through the moving portal to see what happens.
by the logic of A the object maintains its momentum relative to the entry portal (its original frame of reference), while B is relative to the exit portal (the exit portal's frame of reference). If you shoot a cube straight through the portal while it's moving (at a flat angle, you'll have to time it right) if A is right it will come out going straight forward and if B is right it will come out at an angle based on the relative speed of the entrance portal, if I remember right the portals are moving downward so that means the cube should go slightly upward when it exits

The portal is inactive while it moves in that bit.

Additionally, people have tried it with mods and the results differ based on the physics simulation. The game does not provide an answer because it wasn't designed to accommodate this scenario.

>If you shoot a cube straight through the portal while it's moving (at a flat angle, you'll have to time it right) if A is right it will come out going straight forward and if B is right it will come out at an angle based on the relative speed of the entrance portal, if I remember right the portals are moving downward so that means the cube should go slightly upward when it exits
I'm afraid I don't follow.

hm, yeah I should've guessed

how I think of the scenario in my head is if you're looking through a stationary portal at the exit of a moving portal, you'd see the whole world as if it was moving, although in reality the portal is what's moving. If you shoot something through the portal at a flat angle, and for sake of simplicity let's say the object is moving at the same speed as the portal, which is descending, from the perspective of someone looking through the portal the object is approaching at an upward 45 degree angle, and when it passes through it would continue in the same direction

Portals may be in every direction relatively to each other.
I think that the cube gets out of the blue portal with some speed because of the relative movement of the cube relatively of the yellow portal. In-game Portal don't conserve momentum since it can change your speed orientation. They don't conserve potential energy either, consider gravitational energy in some setups

Oh, yeah, that makes sense.