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Tolismir

A or B?

Valisa

A

Sandrika · Post edited by Sandrika at 2012-02-02 16:59:45

A

Edit:

Actually could be "B" if there is a magnet that we cant see out of the pic, or if "B" opens to a universe that gravity is reversed.... just saying.

Varo

A

Hoff

A. Momentum is transferred through the portal, not velocity. The cube has no momentum, therefore once it is through the portal, it will simply obey the laws of gravity. At least, this is my understanding.

swirly

Not having actually played that game, I'll go with A.

jasminie

C

Arzozah

A

Zurena

Swirly - I highly recommend playing it! (It runs on Macs under Steam.)
A for the reasons Hoff said. '''' and here are my spare apostrophes that I keep trying to put in plural words. Please take them and put them to proper use.

Tolismir · Post edited by Tolismir at 2012-02-03 09:25:51

Does this change anyone's answer?

Hoff · Post edited by Hoff at 2012-02-03 09:38:21

Not mine, no.

Well...maybe.

Hoff

After some thought, no.

Picture the blue platform lying flat, instead of at an angle. It then essentially becomes like the orange "cylinder" crashing down on the cube. The area "inside" the "cylinder" would be the area above the blue portal. Ergo, it's really no different than, say, a hula hoop being slammed down around you from some distance up.

The diagram is that, but with the blue portal at a diagonal.

I'd love it if someone who has actually studied physics could confirm/deny.

' ' celebratory apostrophes ' '

hronk

I'd say A too, as a person who has studied physics and with the caveat that this is not really physics. It's just 'how one would typically expect things to behave, were there magical things such as portals'. What the engine does, in its current implementation, doesn't really change that.

One physics-nerdy thing might be that a 'moving portal' doesn't really make sense if a portal is a thing that connects one region of space to another. You can't move a region of space (usually).

Jexii

Does the portal actually have resistance? Or would it if it were a real thing? If so, then we'd need to know more like how fast was the moving portal moving, is the amount of resistance upon entering different from that on exiting? For example if there is a lot of resistance before entering than maybe it would be enough to get the cube moving. Or maybe it would never actually emerge out of the other side if there was too much resistance to exit the portal. Is there more resistance going in than going out? Or is a portal totally resistance free?

In summary: if the portal had more resistance exiting than the amount of force applied, than maybe the cube gets stuck in the portal and never exits. If the portal has no resistance, then I'd say A. If the portal has more resistance going in than could B be true or at least a bit true?

Valisa · Post edited by Valisa at 2012-02-03 19:54:37

It's like trying to hit the cube with an open door.

Jexii

So what prevents the cube from falling back through the other way?

hronk

Sure, if the portal acted as a sort of membrane that required force to break through, you could get the cube to bounce out the other side. But the portals in portal don't.

Valisa

Jexii said:
So what prevents the cube from falling back through the other way?

In this case, the press is (I assume?) still pressed down, blocking the other way. Also, the cube is plopped on the ground. I don't think B can be true in any way unless it sucks it in.

I don't think the portal has resistance at all in this case, though. If I remember correctly, two portals side by side on the ground keep a cube bouncing until it falls away.

hronk

What's keeping it from falling back through is the platform that's holding it in place in the first place.

swirly

The platform that is on the other side of the portal would be at the same slope as the wedge, and then gravity would take over. You're basically hitting something with a hole, and a hole does not move; the thing with the hole in it moves.

Take the two examples above: the hula hoop and the open door frame. If you drop a hula hoop over your head, the hole has absolutely no effect on you; it's a hole. The speed at which the hula hoop drops has no effect on you because you never interacted with the hula hoop. If you work on a movie set and you stand there while someone moves a wall with a door in it such that you go through the open doorway, the speed at which the wall moved has no effect on you because you never interacted with the wall. The open doorway has no effect on you; it's a hole.

From what I've seen of the game, the portal acts as a hole. If you shoot a cube through it, going through the portal does not change the speed at which the cube exits. If you step through a portal, your speed does not change-- you do not encounter any change in resistance; it's effectively an open doorway.

To add a third example, let's assume that the hole is a manhole on the hill that Lombard St is on (or for locals, Vermont St), but the twisty section of the street has been straightened; we have magic now that lets us go up and down that block in a straight line. The platform behind the manhole cover is at the same angle as the hill; you are standing on this platform at a 90 degree angle to that platform. Assuming that you are facing downhill and you have no arms with which to break your fall, you will fall on your face and then slide down the hill in the scratchiest way possible.

Having watched only the first half of that video, there is one thing that is clear: the physics engine isn't coded to handle this case. You have to change settings to enable portals on moving objects and even then, you encounter MAJOR bugs. So the question isn't really "what DOES the physics engine do?", but "what SHOULD the physics engine do?" Well, the physics engine usually treats the portal as a hole and should continue to treat the portal as a hole.

/me demonstrates the sound of one hand clapping and then points out that the definition of sound requires interaction with an ear.

Jexii · Post edited by Jexii at 2012-02-04 00:15:45

How do you know the platform is at the same angle as the other portal? What law dictates that you must portal to a world with similar gravity and similar alignment to the center of gravity? Also, why assume that the platform stays in place? Maybe it moves up and down? From the picture you can't tell that.

We did not study portal physics in my physics major....

swirly

If the platform were not at the same angle as the hole, the cube would not be shooting perpendicular to the hole on exit. If one platform in a scientific illustration has motion lines and the other does not, it is reasonable to assume that the one without does not move.

But yes, the other side of the portal could be in the Hollow Earth.

Jexii

I know nothing about the game and assuming I'm not considering the video, my point is that the picture tells you very little info, not nearly enough to conclude A or B without making a lot of assumptions. For example, I assumed the second illustration was stationary to swirly's point about lack of motion lines on the right seems reasonable. But I was wondering how we knew the platform on the left wasn't immediately going to go back up. I don't think the trajectory in B is any indication that they are on the same angle relative to the center of gravity as the moving platform. I assumed B was the option if the portal/moving pair had any kind of force behind it to push the cube through the portal, that's where the questions on portsl resistence came from.

So either you assume the two pieces are in the same space like as shown in the picture, then they wouldn't be on the same angle and my question of why the box doesnt't just fall back down is still one I'm curious sbout, or If you can't assume its the same space then it could really be any combination, the AB pair could be in space or on another planet for all we know.

All very interesting for sure.

hronk

Good grief, Mexico, did they replace you with some Puzzle Conspiracy Theorist while you were in China? Yes, you some assumptions have to be made but for anyone who's played the game (and looked at a diagram, or lived on planet Earth) they are pretty straightforward. Also they are very much in the same space. The same room, even, as in 99% of the game.

All very interesting for sure

I was hoping it might be interesting and that there's going to be some sort of clever or funny surprise but as a 'puzzle' or whatever this is, it's pretty dumb. It's unclear to people who haven't played the game and it's pretty much a non-question to anyone who has (weird digression of some dude into the game engine editing tool notwithstanding). It certainly doesn't deserve the "plane on a conveyor belt" treatment we're giving it!

Jexii

Well you know, I did say that I know nothing about the game... I didn't realize that only people that had played the game or even knew this was associated with the game were allowed to comment.

hronk

Everyone's allowed to comment! The plunger on the right goes down and then goes back and to the left (and back and to the left) and to the grassy knoll!

Hoff

It's a discussion of a theory, nothing more, and some of us are enjoying it. There's also zero reason to assume the two portals are in the same room if you have never played the game, other than "well they're right next to each other in the diagram," which isn't much of a reason at all. I enjoyed reading the thread and also found it very interesting. I'm very irritated by being told that something I'm enjoying and interested in is "dumb" or doesn't deserve the attention it's receiving.

hronk

I think the 'puzzle' is dumb, without quotes. Yes, there is zero reason to assume X or Y and as I said, it's pretty confusing if you haven't played the game and entirely straightforward if you have. I can think a puzzle is dumb, that it's generating more heat than light and still enjoy reading and posting to the thread! Perhaps so can you!

Valisa

Leonid · Post edited by Leonid at 2012-02-04 21:23:06

Why would the cube move at all...seems like at that angle of slope it would just stay there...until the plunger went back up...

yroa

When the plunger "pushes" the cube through the portal by completely covering the platform that the cube is resting on, I have to assume that surface of that platform becomes the surface of the angled platform that we're looking at for A and B. Basically it's at rest on the same piece of matter as it was before, it's just located somewhere else in space.

B is unpossible, I think we can all agree on that. There's no force being applied that could fling the cube anywhere. The only argument that's valid, I think, is between A and C (where C is the cube just sitting there doing nothing). It's a toss up, at this point, because I don't know what the level of static friction between the cube and the top of the platform that it's resting on is. If it's stronger than whatever gravity is applying (looks like a 45 degree angle, so sin(45) * x * (9.8) where x is the unknown weight of the box) then C happens, else A happens. The coefficient of friction between steel on steel is .74, I guess, and those parts look pretty smooth - so that's cos(45) * x * (9.8) * .74.

I think we can take out the weight, because it's all multiplication, so 6.9 is what gravity is applying and in order to start moving we need 5.1. I'm going to say that A is true. It looks like anything over 37 degrees with a mu of .74 will slide due to gravity alone.

Keep in mind that physics was a long time ago and this is back pain induced napkin math. I'm sure Hronk will stomp my logic, that dude is wicked smrt.

Bellaluna

and then I ate a sandwich

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