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The Community => Open Discussion => Topic started by: zman9000 on 30, May, 2012, 02:37:36 AM

Title: Immovable object [vs] unstoppable object
Post by: zman9000 on 30, May, 2012, 02:37:36 AM
It has been thought of by many people over time. two objects collide one cannot be stopped the other cannot be moved. what would this epicly impossible showdown be like in the real world.

Well my thoughts on this is I believe they would both win, and this is why:
[spoiler]for both objects do act the same in the real world they would have to have infinite mass.

so stop an object with infinite mass you have to have the same amount of energy and force. the same goes for moving a stationary object with infinite mass.
both have the same mass and energy. though it is infinite they are both the type of object, one is just moving the other is not.

when the collide the energy of motion transfers from the moving object to the unmovable one. being infinitally dense means that the energy transfers perfectly and completely. In the end you would still have an Immovable object and an unstoppable object, they would have just switched roles.[/spoiler]

So lastly if you are wondering why i made this topic when i think i have all the answers, well i don't, this is just my theory on how it would work.
I'd like to get some activity back to the site so, post what your take is on this impossible scenario.
Title: Re: Immovable object [vs] unstoppable object
Post by: Misery on 30, May, 2012, 03:24:00 AM
(http://i1185.photobucket.com/albums/z345/NightEyeDie/impossiburu.jpg)

If both objects have infinite mass, wouldn't they have to be the same object?
Logically, one or both objects would have to cease to exist. It's the only thing I can think of that doesn't contradict their unstoppable/immovable states.
Title: Re: Immovable object [vs] unstoppable object
Post by: Atrius on 30, May, 2012, 04:02:22 AM
For such objects to exist there would have to be zero transfer of energy when they collide with other objects.  Based on this fact there are two possible scenarios:

1)  After the collision both objects retain the same momentum, but it's direction is changed.  The unstoppable object bounces off the unmovable object without slowing down at all.

2) They are intangible, and do not interact with each other.  The unstoppable object passes through the unmovable object as though it does not exist.
Title: Re: Immovable object [vs] unstoppable object
Post by: Rockisftw on 30, May, 2012, 04:37:52 AM
Quote from: Atrius on 30, May, 2012, 04:02:22 AM
For such objects to exist there would have to be zero transfer of energy when they collide with other objects.  Based on this fact there are two possible scenarios:

1)  After the collision both objects retain the same momentum, but it's direction is changed.  The unstoppable object bounces off the unmovable object without slowing down at all.


I think he means that the first object cannot be stopped period, and a change in direction requires some give in the object. So the point is, between something that will knock everything away in its path vs something that cannot be moved no matter what.. whats going on.
Title: Re: Immovable object [vs] unstoppable object
Post by: Aile~♥ on 30, May, 2012, 11:51:38 AM
Yeah, they'd just go through each other, I think. Or the universe would cease to exist. DIVIDE BY ZERO ERROR.
Title: Re: Immovable object [vs] unstoppable object
Post by: zman9000 on 30, May, 2012, 12:59:57 PM
QuoteYeah, they'd just go through each other, I think. Or the universe would cease to exist. DIVIDE BY ZERO ERROR.
And you see there is where the problem comes when people think about this. when you run a computer program on this, it comes up with an error.
And i wasn't talking about the question in general. I was saying: OK say these objects, like the size of... a bowling ball, were to collide in the real world how would they react.
since for an object to be unmovable or unstoppable in the real world, it would need infinite mass, and be infinitely dense.

technically this would make them act the same as the question. as for colliding the = the same mass/density as each other. And speaking about transfer of energy, something infinite hitting some infinite would have instant transfer of energy as there is no space for energy to move other then the other target.

And another thing i realized when reading back over your comments. say we take infinite density out of it, and just have infinite mass. there is a way for this to still be possible due to the very description of this event.
[spoiler]
Infinite means goes on forever.
now something we should have all learned in math using graffing and/or number lines as an example.
say you have two lines, the first starts at one point and goes in one direction forever. The second also starts at one point but goes in opposite directions forever.

it would look like this written visually
L1:                       |--------------->
L2: <--------------|-------------->

They are both the same length. because (infinite * infinite) = infinite.

so think two objects with infinite mass like this
<=====|       |=====>

they just go on forever in one direction. this proves you can have more then one object with with infinite mass interact with each other.
[/spoiler]
[spoiler]
QuoteIf both objects have infinite mass, wouldn't they have to be the same object?
no they wouldn't, there are ways that it still works with out it taking up all space in this given event area. since half of infinite is still infinite. you can have an infinite number of infinite mass objects in an infinite space.

QuoteLogically, one or both objects would have to cease to exist. It's the only thing I can think of that doesn't contradict their unstoppable/immovable states.
this is half true, as it is, the most logical thing would be to say one goes away. but what would happen if you also said not only can they not move/be stopped but they were also indestructible?

the weird thing would be this, no the universe wouldn't go away. yes the objects could collide, the moving one would keep moving, the one that doesn't move wouldn't move, they wouldn't be destroyed, pass through each other, or anything else.
if you take it out of a real world setting and go for the literal "Immovable object", unstoppable object", this creates a paradox, yet just because of the paradox doesn't mean said universe goes away. you can't even comprehend this.[/spoiler]

finally there are three types of settings for this that people tend to lean to as their example.
universal shutdown since something happens that can't happen, the universe goes away. (this is in line if you think about it like a computer would)
real world example using what we know about how matter interacts. (this is in line if you think about how things that aren't real would work with our rules)
Cop-out example by ignoring the rules of how things work completely. (this is in line if you understand its impossible but feel there must be a right answer)
Title: Re: Immovable object [vs] unstoppable object
Post by: leaf on 30, May, 2012, 01:41:41 PM
Hey zed, you actually made an interesting thread. Congrats.

Now, for a serious reply:
You're taking several assumptions that are not stated in the problem outline that renders the problem as overdefined. Who said the objects were the same size, for example? What if you had a very tiny particle, capable of fitting between the gaps in a much larger solid? The very tiny particle passes through the solid without stopping or slowing down, while the solid remains stationary. This satisfies the initial conditions, does it not? While not technically a "collision," one object has intersected with the surface plane of the other object.

If you must take the term "collision" literally, then atrius's solutions are the only possible ones. As it is now, the event of a strictly defined unmovable object and a strictly defined unstoppable object colliding is only a theoretical construct. It is not that the world would collapse if they existed in the real world, or that the objects themselves would cease to exist; they simply could not exist in the first place. If such objects ever did exist and entered such a collision, they would be redefined on the spot to fit within the bounds of the real world (which would result in one of the solutions atrius proposed).
Title: Re: Immovable object [vs] unstoppable object
Post by: zman9000 on 30, May, 2012, 02:05:36 PM
Ah yes, now you have explained it like that i see what you mean.
I was taking it as colliding and I suppose I was more talking about how it would work if i said. hey i have two objects here with infinite mass and density, one isn't moving, one is going to hit the other, what would happen?

technically the way i explained it is a little backwards. since it is technically using a stoppable, and movable object.
Wait... does mean we were kinda sorta almost on the same page?
Title: Re: Immovable object [vs] unstoppable object
Post by: leaf on 30, May, 2012, 05:02:03 PM
Sorta. Your answer (using two objects of infinite mass) is probably fairly close to a real world equivalent. If you assume a perfectly elastic collision of equal masses (a highly erroneous assumption, but we'll go with it for now), their velocities will switch places and the "immovable" object will become "moving and unstoppable" while the "unstoppable" object will become "unmoving and immovable." The problem with this assumption is that "infinite" is not a defined quantity; both (infinity - infinity) and (infinity/infinity) are undefined. Furthermore, while some collisions in real life can approach perfect elasticity, afaik, there is no way to create a true perfectly elastic collision. The problem ultimately reduces to which object is "more infinite," which we have no way to measure, and as such, the problem is unsolvable.

The other problem is that this model neglects gravity. Two objects of infinite mass will create a very large gravitational force. F = G*m1*m2/r^2. If we assume the objects are an infinite distance apart, the equation reduces to infinity^2/infinity^2, which is undefined. If we make the assumption that the objects are infinitely large, it is possible to force a collision in this state. If this problem reduces to any finite non-zero answer (for example, if F = G), the "immovable" object will lose immediately, as it will be pulled by the "unstoppable" object. The "unstoppable" object would then lose on collision. In this case, the immovable object loses first, but in the end, they both lose.

Since the assumption of two objects of equal, infinite mass obviously creates unsolvable contradictions, let's explore some different models. These are the conditions that need to be fulfilled, both before and after the collision:
Immovable object: X = 0, v = 0, a = 0
Unstoppable object: X = v0*t, v = v0, a = 0

If you're using traditional Newtonian physics of two simple spherical objects of some given mass colliding, a solution using these boundary conditions is impossible. The only solution is the trivial solution where no collision takes place, which could be represented by one or both objects being intangible (and therefore passing through each other).

But, what if we expand the problem statement to encompass non-spherical objects in collision? The problem never specified what these objects looked like or how they collided. Non-homogeneous objects should be perfectly acceptable within the bounds of the problem statement.

The biggest problem is in how to model the "immovable" object. How literally should this be taken? If you take "unmoving" literally down to a micro scale, it would imply the object is held at absolute zero. This would imply that not even the atoms are moving. While this could be a legitimate model of an "immovable object," you would have the problem of how to prevent energy transfer to the system (neglecting the fact that true absolute zero is impossible to achieve, and that if it ever were, it may exhibit properties we have yet to see in systems that merely approach absolute zero). Therefore, I propose that the molecular motion be neglected. The "immovable object" can thus be modeled simply as a mass that does not exhibit any change in center of gravity during a collision.

By modeling the "immovable object" as an infinite spring of zero stiffness and zero mass attached to a small cube of some small finite mass, this condition is fulfilled. The spring can be compressed infinitely without ever exhibiting a change in the center of gravity of the object, since the spring itself contributes no mass; the center of gravity is always located at the center of the cube. However, since the spring has zero stiffness, any object that collides with the spring will transfer no force to the cube, causing the cube to remain immobile even from extremely high energy collisions.

The next problem is modeling the "unstoppable object." For this, we will use a sphere of infinite velocity and some small finite mass. Since a finite number times infinity is still infinity, the momentum of this object is infinite. Thus, by definition, an object with infinite momentum cannot be stopped by an object with finite momentum. Furthermore, since the mass is small and finite, gravity can be neglected.

Finally, we move on to the collision. The sphere collides with the spring which is compressed infinitely. The cube remains stationary throughout the process and the sphere never ceases movement. Both conditions of "immovable" and "unstoppable" are fulfilled simultaneously, leading to a possible solution to the problem.

Q.E.D.
Title: Re: Immovable object [vs] unstoppable object
Post by: Misery on 30, May, 2012, 05:44:56 PM
I think I've found a conclusive answer to the question of "what happens when an unstoppable object collides with an immovable object"
and it's not the more realistic "they don't"

The unstoppable object keeps moving in the same direction, and the immovable object retains its exact same position and form.

Though technically, that only describes what happens after they collide... so what happens when they collide? That's still open for discussion.
This has gotten me thinking about some other things though.

Saying that an object is "immovable" assumes a static universe of finite space where everything has an exact position. What constitutes an immovable object? What is it immovable in relation to? Can such an object even exist?[spoiler]I believe the answer to the last question is "yes, if the object occupies an infinite space"[/spoiler]Can an object of infinite mass exist within a finite space?[spoiler]Again, I believe the answer is yes, but the space it occupies cannot be defined. I'd explain why I think that, but
1: I'd like to see if anyone else reaches the same conclusion in the same way, and
2: I'm lazy[/spoiler]
The other things I thought of mostly relate to infinity and these two questions...

In response to leaf's post: Is infinite velocity actually possible?
Title: Re: Immovable object [vs] unstoppable object
Post by: leaf on 30, May, 2012, 06:03:16 PM
Probably not. I realized a bit after posting it was impossible and I was wondering if anyone would actually catch me on that before I got to fix it =p

Anyway, for an accurate solution, that can be fixed by making the sphere of mass = m1 and the cube of mass = m2 = m1^2, where m1 = infinity. The new boundary conditions become m1 always has v > 0 in the positive x direction and m2 always has v = 0, a = 0, and x = 0 with respect to an inertial reference frame.

Or at least, that's one possible fix to the gravity problem. Another fix would be to have a third mass of mass of m3 = m1 approaching the cube from the opposite direction. There is also an infinite spring of zero mass and zero stiffness extended in this direction. Then, the two unstoppable objects and the one immovable object will remain unstopping and unmoving, respectively.

So, to summarize, the unstoppable object is defined as a sphere of arbitrary size, arbitrary (and finite) velocity in the positive x-direction, and mass m1 = infinity. The immovable object is defined as a massless infinite spring with zero stiffness that extends in the negative x-direction from the origin, which is attached to a cube of arbitrary size with mass m2 = m1^2 and a = 0, v = 0, x = 0 with respect to an inertial reference frame. The sphere collides with the spring and compresses the spring infinitely, never slowing down or changing direction. The cube does not move from its inertial reference position.

Q.E.D.

---

To answer your questions: An object of infinite mass could occupy a finite space if it also had infinite density. You are also correct that the space it occupies cannot be defined, since infinity divided by some finite value is still infinity, and infinity divided by infinity is undefined.
Title: Re: Immovable object [vs] unstoppable object
Post by: zman9000 on 30, May, 2012, 06:19:59 PM
Quotemore infinite
eh well... ok

I always thought of it like this, before i put more thought into it.
[spoiler]two objects that are exactly the same.
they are 100% solid in the true meaning of the word, and they them self's are solid and none moving with in them self's
one is fixed to a plain and can not move nor transfer energy. a perfect unmovable object.
the other is sent toward the other on a straight linear path that it can not deviate from and the path directly intersects the center of the non moving object.
the speed doesn't matter.
the rules are:

Object 1 must stay where it is no matter what.
Object 2 must stay on the path and must never slow or stop.
lastly matter may not intersect other matter.

to bad this its self is truly something impossible to think about or even replicate since the collision of the two objects following these rules brake the rules.[/spoiler]

This is the same thing as a few other variations I've heard.
[spoiler]A sword that can cut through anything meets a shield that can not be cut.
A force that can destroy anything meets an object that can't be destroyed.
Glue that sticks to everything and an object that doesn't let anything stick to it.

The only thing we know is we can never know what would happen.[/spoiler]

QuoteSaying that an object is "immovable" assumes a static universe of finite space where everything has an exact position. What constitutes an immovable object?
I think the bigger question is what constitutes a point within said universe for said object to reside?

QuoteCan an object of infinite mass exist within a finite space?
I've already said, an infinite number of infinite objects can fit in an infinite space EDIT::(and density doesn't have anything to do with it). but it is also possible for only 8 to do so, or 4, or 2, or 1, or a certain number. as long as you are talking about 3d space this holds. cause i don't want to get into 4D talk again... that was a nightmare.
Title: Re: Immovable object [vs] unstoppable object
Post by: leaf on 30, May, 2012, 06:30:27 PM
Yeah, you're overconstraining the problem, which is why you get a paradox. It's the same as if you were to say y = 2x and you decided you wanted to make y = 1 and x = 2 instead of the other way around. If there were a z term in there, say, y + z = 2x, then you could do this and the equation would still hold (in that case, z = 3). But, if there is no z, the problem is overconstrained and no solution can be found; the result is just nonsense. 1 does not equal 4.

Since you assume both objects to be rigid bodies, a solution is impossible. One of the objects has to be a spring.

Alternatively, the "unstoppable object" isn't an object in the truest sense of the word, but is instead a wave. The problem is waves experience interference and such, so I'm not sure if it would be entirely accurate to call waves "unstoppable." Especially since they require something to propagate through.

edit: And zed, you misread the question. He was asking if it could fit in a FINITE space, not an infinite one.

QuoteA sword that can cut through anything meets a shield that can not be cut.
A force that can destroy anything meets an object that can't be destroyed.
Glue that sticks to everything and an object that doesn't let anything stick to it.
These are less scientific, but... okay.

The sword will cut anything that it strikes. The shield will not be cut by anything that strikes it. The solution is trivial. The sword will miss at any attempts to strike the shield.

The force is infinite. The object can withstand infinite stresses. According to your theory of infinity (which is wrong, btw), the object that cannot be destroyed wins, since the stresses in the object did not surpass their limit (which is infinity). The actual winner depends once again on which is "more infinite": The force or how much force the object can withstand. This is basically the problem statement you made before but with rigid bodies (which is, as stated, unsolvable).

Glue that sticks to everything would stick to the object that nothing sticks to, but it would easily wipe off. =p
Title: Re: Immovable object [vs] unstoppable object
Post by: zman9000 on 30, May, 2012, 06:55:20 PM
QuoteYeah, you're overconstraining the problem, which is why you get a paradox. It's the same as if you were to say y = 2x and you decided you wanted to make y = 1 and x = 2 instead of the other way around. If there were a z term in there, say, y + z = 2x, then you could do this and the equation would still hold (in that case, z = 3). But, if there is no z, the problem is overconstrained and no solution can be found; the result is just nonsense. 1 does not equal 4.
well i get what you mean, but just because the result is nonsense doesn't mean its not a result. but i think i get what you...

QuoteSince you assume both objects to be rigid bodies, a solution is impossible.
what i mean about th...
QuoteOne of the objects has to be a spring.
or...
Quotethe "unstoppable object" isn't an object in the truest sense of the word, but is instead a wave.
maybe you don't...

i feel like your solution is kinda is off but... idk... but reading it gave me another idea.
what if one of the objects was "dark matter" and the other normal. (and maybe i'm just going end up with the same answer you got just slightly different.)
If you don't know, dark matter now refers to something we have actually found and studied. dark matter only interacts with normal matter through gravity, but it has the same amount of gravity as normal matter.

with one object dark matter and the other one normal matter, both can have the same mass and size, and follow all three rules i said in my other post. but they don't collide.
but also with this, gravity would still be a factor... and since i really haven't been doing to well with the math... eh i'll leave it up to leaf.

Despite how this post started, he might be on to something...
Title: Re: Immovable object [vs] unstoppable object
Post by: Misery on 30, May, 2012, 07:05:51 PM
Quote from: zman9000 on 30, May, 2012, 06:19:59 PM
QuoteSaying that an object is "immovable" assumes a static universe of finite space where everything has an exact position. What constitutes an immovable object?
I think the bigger question is what constitutes a point within said universe for said object to reside?
That's the point exactly, since the universe (presumably) expands infinitely in all directions, we have no way of knowing wether the "immovable" object actually remains at the same position. I already mentioned the only possibility I can think of, an object occupying an infinite space, but that would mean the other (unstoppable) object cannot exist unless it's inside the immovable one.

Quote from: leaf on 30, May, 2012, 06:30:27 PMSince you assume both objects to be rigid bodies, a solution is impossible. One of the objects has to be a spring.
By disregarding molecular motion, the immovable object could be just about anything. And of course a solution is impossible, the initial question doesn't describe anything that could actually happen in reality to begin with, not even theoretically. We're not here for an answer, we're here for discussion ;)

Quote from: leaf on 30, May, 2012, 06:30:27 PMedit: And zed, you misread the question. He was asking if it could fit in a FINITE space, not an infinite one.
Adding to that, I think infinite density would be a result rather than a condition. It probably doesn't matter though.

Quote from: zman9000but they don't collide.
The question implies that the two objects must collide.
Edit: No wait, the question clearly states that they must collide.
Title: Re: Immovable object [vs] unstoppable object
Post by: zman9000 on 30, May, 2012, 07:15:27 PM
QuoteThat's the point exactly, since the universe (presumably) expands infinitely in all directions
nononononono stop there... that isn't the reason... like you said "presumably". My point is, even with two objects the only way to know location is to reference something else. but i pointed it out more or less as a joke as since there are only two objects being in play, you would only need relative location for said experiment to work.

QuoteBy disregarding molecular motion, the immovable object could be just about anything. And of course a solution is impossible, the initial question doesn't describe anything that could actually happen in reality to begin with, not even theoretically. We're not here for an answer, we're here for discussion ;)
you don't mind if i thumbs you up and give you a coin do you?

QuoteAdding to that, I think infinite density would be a result rather than a condition. It probably doesn't matter though.
it only depends if you are trying to place this in the real world physics, or if you are taking the exact meaning of the words Immovable and unstoppable.

QuoteThe question implies that the two objects must collide.
this brings up another good point. since when does matter collide?
Title: Re: Immovable object [vs] unstoppable object
Post by: leaf on 30, May, 2012, 07:24:15 PM
Quote from: zmani feel like your solution is kinda is off but... idk...
How so? Unless you can find something I forgot to account for, it accommodates all conditions of the problem.

Quote from: zmanthis brings up another good point. since when does matter collide?
Son, you just went full retard.

Quote from: Misery on 30, May, 2012, 07:05:51 PM
Quote from: leaf on 30, May, 2012, 06:30:27 PMSince you assume both objects to be rigid bodies, a solution is impossible. One of the objects has to be a spring.
By disregarding molecular motion, the immovable object could be just about anything. And of course a solution is impossible, the initial question doesn't describe anything that could actually happen in reality to begin with, not even theoretically. We're not here for an answer, we're here for discussion ;)
Not true. While certainly, if you only needed an immovable object, you could make do with a rigid body. But the the point was to come up with a way for an immovable object and an unstoppable object to collide, while still keeping true to the conditions of being immovable and unstoppable. One or both objects could not exist in the same world if they did not properly interact with each other, after all. There may be other solutions that don't involve a spring, but that doesn't change the fact that using a very specifically defined spring (massless, infinite, and zero stiffness) will give a working solution.
Title: Re: Immovable object [vs] unstoppable object
Post by: Misery on 30, May, 2012, 07:33:44 PM
Quote
QuoteThat's the point exactly, since the universe (presumably) expands infinitely in all directions
nononononono stop there... that isn't the reason... like you said "presumably". My point is, even with two objects the only way to know location is to reference something else. but i pointed it out more or less as a joke as since there are only two objects being in play, you would only need relative location for said experiment to work.
The question of wether an immovable object can actually exist was unrelated to the unstoppable vs immovable question...

Quote
QuoteAdding to that, I think infinite density would be a result rather than a condition. It probably doesn't matter though.
it only depends if you are trying to place this in the real world physics, or if you are taking the exact meaning of the words Immovable and unstoppable.
Another one of my unrelated questions...

Quote
QuoteThe question implies that the two objects must collide.
this brings up another good point. since when does matter collide?
Quotetwo objects collide one cannot be stopped the other cannot be moved.
I assume these objects consist of matter, and the objects collide
But I'm not great with physics -.-

Quote
Quote from: Misery on 30, May, 2012, 07:05:51 PM
Quote from: leaf on 30, May, 2012, 06:30:27 PMSince you assume both objects to be rigid bodies, a solution is impossible. One of the objects has to be a spring.
By disregarding molecular motion, the immovable object could be just about anything. And of course a solution is impossible, the initial question doesn't describe anything that could actually happen in reality to begin with, not even theoretically. We're not here for an answer, we're here for discussion ;)
Not true. While certainly, if you only needed an immovable object, you could make do with a rigid body. But the the point was to come up with a way for an immovable object and an unstoppable object to collide, while still keeping true to the conditions of being immovable and unstoppable. One or both objects could not exist in the same world if they did not properly interact with each other, after all. There may be other solutions that don't involve a spring, but that doesn't change the fact that using a very specifically defined spring (massless, infinite, and zero stiffness) will give a working solution.
Assuming you don't count molecular motion as motion, then sure, it's a working solution. And if you count collision with no mass as an actual collision, but then you could simply say the object itself has no mass.
Title: Re: Immovable object [vs] unstoppable object
Post by: zman9000 on 30, May, 2012, 07:50:36 PM
Quote
QuoteQuote from: zman
this brings up another good point. since when does matter collide?
Quote from: leaf
Son, you just went full retard.

maybe i should make another topic... but not until i figure out how that topic could last longer then one post of be talking about the facts...


Quote
QuoteQuote from: zman
i feel like your solution is kinda is off but... idk...
Quote from leaf
How so? Unless you can find something I forgot to account for, it accommodates all conditions of the problem.

well I just don't like your answer, while it is correct with the way it was set up... I just can't except your... spring... idea...
You don't know, but i once had a real life discussion on this, for about 12+ hours over a few day on a road trip... i had pulled the spring idea then...  and i was shot down like a fly with a nuke...

my take on it is, both have to be a solid zero energy object. one moves never stopping, the other never moves. I'm not sure if you are going for real world example or not... a spring like this... its just... the spring changes direction and speed... i don't know anymore
Title: Re: Immovable object [vs] unstoppable object
Post by: leaf on 30, May, 2012, 08:10:15 PM
Quote from: Misery on 30, May, 2012, 07:33:44 PM
Assuming you don't count molecular motion as motion, then sure, it's a working solution. And if you count collision with no mass as an actual collision, but then you could simply say the object itself has no mass.
Well, saying the object has no mass is actually a problem in this case, since I wouldn't be able to pull the center of gravity voodoo. If both the mass of the cube and the spring were negligible, the center of mass would be wherever the center of the spring-mass construct is, rather than at the center of the cube.

And you kind of have to disregard molecular motion. The problem statement referred to an "immovable" object. Not an "unmoving" one. On a macro scale, at the very least, it is both immovable and unmoving, which is what is relevant to the problem. Perhaps a more accurate way to put it would be to say that it's unmovable through the application of outside force. No matter how much force you apply to that spring, the object's center of mass will always remain at the same coordinate position.

Quote from: zman
well I just don't like your answer, while it is correct with the way it was set up... I just can't except your... spring... idea...
You don't know, but i once had a real life discussion on this, for about 12+ hours over a few day on a road trip... i had pulled the spring idea then...  and i was shot down like a fly with a nuke...

my take on it is, both have to be a solid zero energy object. one moves never stopping, the other never moves. I'm not sure if you are going for real world example or not... a spring like this... its just... the spring changes direction and speed... i don't know anymore
But was your spring massless with zero stiffness? :awe:

And by definition, it's impossible for an object to be moving and have zero energy. In fact, it's impossible for an object to have mass and have zero energy, too.

The only way to solve this problem is to remove implied constraints. You have to define the objects independently. And if you're not going to try to work toward a theoretical solution, there's no point in even discussing it to begin with.
Title: Re: Immovable object [vs] unstoppable object
Post by: zman9000 on 30, May, 2012, 08:37:28 PM
QuoteBut was your spring massless with zero stiffness? :awe:
no, i was ten... but my brother said that part... and he was 8 :awe:/*cry*

QuoteAnd if you're not going to try to work toward a theoretical solution, there's no point in even discussing it to begin with.
we can, just not that one. springs.. just use a rubber Ball or rock... it will have almost the same effect... and besides, an unstoppable object does not slow down, change direction or form.
Title: Re: Immovable object [vs] unstoppable object
Post by: Rockisftw on 30, May, 2012, 09:03:47 PM
I suppose a few things can be said..
Leaf, whats with all de formulas O-o!
Back onto the spring/rigid discussion, if it were between two rigid objects <assuming they are rigid, not springs or waves>; from the point of contact energy would just be exerted in some form or the other, sound, light, heat, etc, unless the "unstoppable" "object" is coming from all sides. In which case, we have to make up something imaginary here..

If it were based on a spring, the energy from an "unstoppable" force/object hitting the "immovable" object that acts like a spring, then the model would roughly equate
=====>|<=====
Yet, due to the very nature of being a "spring" means that it isn't immovable, it merely redirects the force back.
The other idea of it being an object at Absolute Zero <0K> is plausible, because we have absolutely no idea how Absolute Zero works. Mostly everything that we know and can formulate theories on are based on the idea that 0K is impossible. If 0K is possible, then nothing is interacting with it.. <Is that the right word? Maybe I should say influencing instead.> and the object itself is only capable of interacting with others <E.G. Gravity and so forth>. At least, my thoughts anyway.
Whoever said something about
            |======> <Infinity 1>
<====|======> <Infinity 2>
Minus the typing error, assuming the line is of the same origin; Where is the point of collision between the two forces? Don't they technically coexist? Based on the fact that this is also a mathematical equivilent, this graphed is either up or down the Y/X or a function, and if Inf. 1 is red and Inf. 2 is blue, its blue on the -infinity and purple on the +infinity. While coexistance is the word I used, there are probably more precise words, but you should catch my drift.
Title: Re: Immovable object [vs] unstoppable object
Post by: Jiten on 30, May, 2012, 09:16:39 PM
As complex as it has gotten I'll give my influx:  If they collided and possessed infinite energy, the energy would just push away from each other due to the collision and disperse all over the lands. (Implicating that this is on earth) and they'd still collide with each other all day every day.  I think that sometimes, some people push far too deep into the void of thought when the think about things like this.
Title: Re: Immovable object [vs] unstoppable object
Post by: zman9000 on 30, May, 2012, 11:40:13 PM
Quotefrom the point of contact energy would just be exerted in some form or the other, sound, light, heat, etc, unless the "unstoppable" "object" is coming from all sides. In which case, we have to make up something imaginary here..
wow... not to put you down... but i couldn't read/understand half of what you were talking about. but more importently, this quote from you...

energy being released... >_> o boy, and what really got me was this
Quoteunless the "unstoppable" "object" is coming from all sides.
where do i start... first off there is no energy being released as said objects are not breaking down...

and coming from all sides... explain to me how a solid object can hit something from all sides... and please leave the portal physics out of this.
Title: Re: Immovable object [vs] unstoppable object
Post by: leaf on 31, May, 2012, 12:28:44 AM
If it's a gas exerting pressure on a solid, perhaps? That said, rock's post greatly confused me, too.

QuoteLeaf, whats with all de formulas O-o!
Uh... I haven't really been using many formulas here. I've been applying principles that have formulas associated with them, but it's not like I've been throwing a wall of formulas at you.

QuoteBack onto the spring/rigid discussion, if it were between two rigid objects <assuming they are rigid, not springs or waves>; from the point of contact energy would just be exerted in some form or the other, sound, light, heat, etc, unless the "unstoppable" "object" is coming from all sides. In which case, we have to make up something imaginary here..
You can make the assumption of a perfectly elastic collision. No energy is lost. No sound, no heat, no light, etc, are released. The total kinetic energy is the same before and after the collision.

QuoteIf it were based on a spring, the energy from an "unstoppable" force/object hitting the "immovable" object that acts like a spring, then the model would roughly equate
=====>|<=====
Yet, due to the very nature of being a "spring" means that it isn't immovable, it merely redirects the force back.
I don't think you quite understand what a massless infinite spring of zero stiffness really means. While I'm sure you understand massless (m = 0) and infinite (its unstretched length is infinite), you may not understand what the physical meaning of zero stiffness really is.

A spring with infinite stiffness acts like a rigid body. It will perfectly resist deformation and directly transfer force from one side of the infinite stiffness spring to the other. A spring with zero stiffness, however, transfers no force. It is perfectly deformed, absorbing no energy in the process. Remember that formula you learned in physics for the spring force? F = kx? Or the potential energy of a spring? E = 1/2*k*x^2? Set k = 0 and see what happens to those. By setting the spring's stiffness to zero, it allows the sphere to collide with the spring and infinitely compress it, without transmitting any of the force to the cube. The sphere remains in constant motion the whole time, and never loses any energy or momentum. Then, since the spring is massless, even though it is being infinitely compressed, the center of mass of the object never changes, and is always located at the center of the cube.

QuoteThe other idea of it being an object at Absolute Zero <0K> is plausible, because we have absolutely no idea how Absolute Zero works. Mostly everything that we know and can formulate theories on are based on the idea that 0K is impossible. If 0K is possible, then nothing is interacting with it.. <Is that the right word? Maybe I should say influencing instead.> and the object itself is only capable of interacting with others <E.G. Gravity and so forth>. At least, my thoughts anyway.
Whoever said something about
            |======> <Infinity 1>
<====|======> <Infinity 2>
Minus the typing error, assuming the line is of the same origin; Where is the point of collision between the two forces? Don't they technically coexist? Based on the fact that this is also a mathematical equivilent, this graphed is either up or down the Y/X or a function, and if Inf. 1 is red and Inf. 2 is blue, its blue on the -infinity and purple on the +infinity. While coexistance is the word I used, there are probably more precise words, but you should catch my drift.
The rest of this is all gibberish. I'm not even gonna try to make sense of it.

---

...however, I will admit, the "unstoppable object" exerting a pressure on the "immovable object" is an interesting idea. Congrats on coming up with that one, rock. If we assume the immovable object to be a particle of infinite mass in an inertial reference frame, we can define the "unstoppable object" as a hollow sphere of dynamic radius. The sphere is always a sphere (it cannot be deformed into a shape that is not a sphere), but it is possible to increase or decrease its diameter with infinite force. Since this is a pressure force, we can choose to have the sphere be compressed. Anything that is larger than the new diameter of the sphere will be crushed to fit within it. This sphere then crushes the immovable object. However, because the immovable object was already a point in space, it is impossible to compress it further than that. The sphere infinitely reduces its size to approach zero radius at the same point in space as the immovable object, but, because it is impossible to reach zero from a finite value, the unstoppable object never actually reaches zero radius. This process continues for eternity. The end result is that the immovable object never moves, and the unstoppable object never stops.
Title: Re: Immovable object [vs] unstoppable object
Post by: Rockisftw on 31, May, 2012, 03:12:47 AM
Quote from: leaf on 31, May, 2012, 12:28:44 AM
If it's a gas exerting pressure on a solid, perhaps? That said, rock's post greatly confused me, too.

QuoteLeaf, whats with all de formulas O-o!
Uh... I haven't really been using many formulas here. I've been applying principles that have formulas associated with them, but it's not like I've been throwing a wall of formulas at you.

QuoteBack onto the spring/rigid discussion, if it were between two rigid objects <assuming they are rigid, not springs or waves>; from the point of contact energy would just be exerted in some form or the other, sound, light, heat, etc, unless the "unstoppable" "object" is coming from all sides. In which case, we have to make up something imaginary here..
You can make the assumption of a perfectly elastic collision. No energy is lost. No sound, no heat, no light, etc, are released. The total kinetic energy is the same before and after the collision.

QuoteIf it were based on a spring, the energy from an "unstoppable" force/object hitting the "immovable" object that acts like a spring, then the model would roughly equate
=====>|<=====
Yet, due to the very nature of being a "spring" means that it isn't immovable, it merely redirects the force back.
I don't think you quite understand what a massless infinite spring of zero stiffness really means. While I'm sure you understand massless (m = 0) and infinite (its unstretched length is infinite), you may not understand what the physical meaning of zero stiffness really is.

A spring with infinite stiffness acts like a rigid body. It will perfectly resist deformation and directly transfer force from one side of the infinite stiffness spring to the other. A spring with zero stiffness, however, transfers no force. It is perfectly deformed, absorbing no energy in the process. Remember that formula you learned in physics for the spring force? F = kx? Or the potential energy of a spring? E = 1/2*k*x^2? Set k = 0 and see what happens to those. By setting the spring's stiffness to zero, it allows the sphere to collide with the spring and infinitely compress it, without transmitting any of the force to the cube. The sphere remains in constant motion the whole time, and never loses any energy or momentum. Then, since the spring is massless, even though it is being infinitely compressed, the center of mass of the object never changes, and is always located at the center of the cube.

QuoteThe other idea of it being an object at Absolute Zero <0K> is plausible, because we have absolutely no idea how Absolute Zero works. Mostly everything that we know and can formulate theories on are based on the idea that 0K is impossible. If 0K is possible, then nothing is interacting with it.. <Is that the right word? Maybe I should say influencing instead.> and the object itself is only capable of interacting with others <E.G. Gravity and so forth>. At least, my thoughts anyway.
Whoever said something about
            |======> <Infinity 1>
<====|======> <Infinity 2>
Minus the typing error, assuming the line is of the same origin; Where is the point of collision between the two forces? Don't they technically coexist? Based on the fact that this is also a mathematical equivilent, this graphed is either up or down the Y/X or a function, and if Inf. 1 is red and Inf. 2 is blue, its blue on the -infinity and purple on the +infinity. While coexistance is the word I used, there are probably more precise words, but you should catch my drift.
The rest of this is all gibberish. I'm not even gonna try to make sense of it.

---

...however, I will admit, the "unstoppable object" exerting a pressure on the "immovable object" is an interesting idea. Congrats on coming up with that one, rock. If we assume the immovable object to be a particle of infinite mass in an inertial reference frame, we can define the "unstoppable object" as a hollow sphere of dynamic radius. The sphere is always a sphere (it cannot be deformed into a shape that is not a sphere), but it is possible to increase or decrease its diameter with infinite force. Since this is a pressure force, we can choose to have the sphere be compressed. Anything that is larger than the new diameter of the sphere will be crushed to fit within it. This sphere then crushes the immovable object. However, because the immovable object was already a point in space, it is impossible to compress it further than that. The sphere infinitely reduces its size to approach zero radius at the same point in space as the immovable object, but, because it is impossible to reach zero from a finite value, the unstoppable object never actually reaches zero radius. This process continues for eternity. The end result is that the immovable object never moves, and the unstoppable object never stops.

I just got out of Chemistry. And when a formula is used, meh. Fact of the matter is I've been up just over 40 hours and it looked like alot to me O-o.
And its called a perfectly elastic collision.. Thanks. I didn't know.
^Hence my level of education error, and the fact that I've always intended a spring to return force.. Like, with a pen.

And the gibberish.. Uhh.. How do I put it;
Someone said something about Absolute Zero which is 0K, and because noone knows how that acts except its particles do not move, nothing has outside influence on it.
So my assumption is it is able to affect other objects, while not being affected by other things.
And by the wierd lines, imagine your standard X/Y graph. One object goes from 0,0 to +infinity, +infinity. Let that line be colored red on the graph.
The second object goes from -inf, -inf to +inf, +inf, and set its territory covered to blue. You end up with purple as the "overlap" which.. do I really have to go over that?
Title: Re: Immovable object [vs] unstoppable object
Post by: leaf on 31, May, 2012, 03:30:19 AM
...I understand that red+blue = purple. I also understand how that graph would look. What I don't understand is what that had to do with anything.

As for the absolute zero stuff, that was actually just supposed to be a way to restrict the immovable object's molecular motion, if that would be a necessary constraint. I don't think it would actually do much for the rest of the problem. In fact, using that condition probably just makes it harder to solve.
Title: Re: Immovable object [vs] unstoppable object
Post by: Rockisftw on 31, May, 2012, 03:42:39 AM
I thought that would've disproven the fact that they are the "same" object as many people have stated, because if they were the same, then the universe is finite and it merely loops upon itself.

Meaning that in the end, they are two different objects which can technically coexist in the same space, at the very least on charts.
Title: Re: Immovable object [vs] unstoppable object
Post by: Aile~♥ on 31, May, 2012, 11:40:42 AM
Umm... what?

Rock, I can't even tell what you're trying to say with that.
Title: Re: Immovable object [vs] unstoppable object
Post by: zman9000 on 31, May, 2012, 10:22:33 PM
QuoteUmm... what?

Rock, I can't even tell what you're trying to say with that.
I think we can all agree that Rockisftw doesn't get this topic at all.
In fact i'm so confused that I almost feel like starting over.......

But at least I think each person should try to sum up their own answer for the problem, as short as possible, but not to short as to confuse people.
I'll then take those and put them in spoilers at the top of the first post with their name. Then we can go through them and discus them.
Title: Re: Immovable object [vs] unstoppable object
Post by: leaf on 01, June, 2012, 01:23:52 AM
I'll just quote myself. Two possible solutions:

QuoteThe unstoppable object is defined as a sphere of arbitrary size, arbitrary (and finite) velocity in the positive x-direction, and mass m1 = infinity. The immovable object is defined as a massless infinite spring with zero stiffness that extends in the negative x-direction from the origin, which is attached to a cube of arbitrary size with mass m2 = m1^2 and a = 0, v = 0, x = 0 with respect to an inertial reference frame. The sphere collides with the spring and compresses the spring infinitely, never slowing down or changing direction. The cube does not move from its inertial reference position.

QuoteIf we assume the immovable object to be a particle of infinite mass in an inertial reference frame, we can define the "unstoppable object" as a hollow sphere of dynamic radius. The sphere is always a sphere (it cannot be deformed into a shape that is not a sphere), but it is possible to increase or decrease its diameter with infinite force. Since this is a pressure force, we can choose to have the sphere be compressed. Anything that is larger than the new diameter of the sphere will be crushed to fit within it. This sphere then crushes the immovable object. However, because the immovable object was already a point in space, it is impossible to compress it further than that. The sphere infinitely reduces its size to approach zero radius at the same point in space as the immovable object, but, because it is impossible to reach zero from a finite value, the unstoppable object never actually reaches zero radius. This process continues for eternity. The end result is that the immovable object never moves, and the unstoppable object never stops.

Both of these meet the conditions that the immovable object's center of mass does not have a change in position, velocity, or acceleration, and the unstoppable object always maintains a positive velocity.
Title: Re: Immovable object [vs] unstoppable object
Post by: Jiten on 01, June, 2012, 11:14:51 PM
It would depend on what kind of energy is is driving the 2 against each other.  Personally,  if it was kinetic energy, I believe it would cause earhtquake.  Massive Tsunamis' would erupt do the vicious seismic activity from the 2 colliding together, ripping apart the earth bit by bit, causing mountains to develop at unrealistic speeds and eventually rip the earth into shards.  However, before that occured, there would be Climate changes with wind patterns and many more omnious things occuring

If it was electric energy, the oceans would be a instant death-trap, followed by vicious lightning surging through the skies, frying innocent people cooking them instantly.  Those who has more metal around them that day might get a bigger dose of lightning while acting as conductors (on a slight margin..) and pass it to other objects and people.  The power would indefinitely go out for the entire earth and it would be a pitch black death with rapid flashes of lightning.

If it was fire, I'm sure the energy scattered would burn the earth with hellish firestorms, ravaging the lands, causing destruction on a wide-edge scale that's so intense, that it would burn up the oceans waters and it would be like a oversized volcano.  Corpses would be charred within a few brief moments, ash in a few more, than ash in lava for the final moments.  Firestorms would be all over the planet like a sprinting inferno until the earth was engulfed in fire.

If the 2 Objects had water....Well this whole world would be blue.  People would drown, heavy rains, tsunamis' of greater capacity would drown everyone despite how high they were and eventually the world would be wiped out.  However it would still stand for each passing day.

If energy clashes with one another, they're bound to disperse offset energy somewhere else due to angles, collision of force,velocity, etc.  too many factors would come into play.  However,  if the main base foundation is purely the energy itself, then quite possibly, velocity & force would have very little to do with the situation of clashing, albeit nothing at all.  The objects would stay in the action that were intended for while they unknowningly ravage the lands to death that the Immovable Obect  & Unstoppable Object are taking place on.  I was under the assumption it was earth.

It's just a 2-hour development of a theory that would seem possible. 

All I can say in the Mist of all of this is this: 
Limitless Possiblities...
There's many other ideas out there in this world that we haven't discovered yet,  so it's unknown for now....

Title: Re: Immovable object [vs] unstoppable object
Post by: Rockisftw on 02, June, 2012, 01:06:14 AM
Quote from: zman9000 on 31, May, 2012, 10:22:33 PM
QuoteUmm... what?

Rock, I can't even tell what you're trying to say with that.
I think we can all agree that Rockisftw doesn't get this topic at all.
In fact i'm so confused that I almost feel like starting over.......

More or less, I was just trying to look at other people's solutions and put out my thoughts on them. Not that I don't get the topic at all, and you really shouldn't have said that.
Title: Re: Immovable object [vs] unstoppable object
Post by: Jiten on 02, June, 2012, 01:21:23 AM

you really shouldn't have said that.
[/quote]

Hm..?  War in the Midst ? Well what are you thoughts on mine Mr. Rock ?
Title: Re: Immovable object [vs] unstoppable object
Post by: leaf on 02, June, 2012, 02:04:15 AM
Ixion... your posts... make no sense... whatsoever.

Earthquakes? Tsunamis? Lightning? Infernos? What? Why? Why would any of that even matter? Who said that this was taking place on earth? And WHY would it be using anything except kinetic and potential energy?
Title: Re: Immovable object [vs] unstoppable object
Post by: Jiten on 02, June, 2012, 02:11:54 AM
Quote from: leaf on 02, June, 2012, 02:04:15 AM
Ixion... your posts... make no sense... whatsoever.

Earthquakes? Tsunamis? Lightning? Infernos? What? Why? Why would any of that even matter? Who said that this was taking place on earth? And WHY would it be using anything except kinetic and potential energy?

I guess I built too much around the Idea ???

Oops.

On a side note, would the Kinetic Energy be even remotely close ?
Title: Re: Immovable object [vs] unstoppable object
Post by: Misery on 02, June, 2012, 07:35:25 AM
hmm, and here I though this topic would die in peace...

Ixion: your post made me lol heartily. Hope you're not going to take that personally, I just thought it was funny.

leaf: regarding your cube with spring solution, there would be no need for the unstoppable object to be an infinite distance away from the immovable one's center of mass - it could just have hit the spring from any direction, and the same conditions would have been fulfilled. But anyway, we don't really have the problem statement of "how would it be possible for [these two objects] to collide?", there's only the simple question of "what would happen?".

It should be noted (although leaf kind of pointed it out already) that it's physically impossible for these two objects to exist in the same universe, unless we go with what Atrius said - they can't interact with each other (which would also mean they can't collide, which gets pretty funny if you think of the spear/shield version of it). There's a very simple reason for this - an unstoppable object is called unstoppable because there exists nothing that can stop it. Vice versa for the immovable one, if there existed unstoppable objects, it wouldn't be immovable.
Title: Re: Immovable object [vs] unstoppable object
Post by: Jiten on 02, June, 2012, 10:05:00 AM
Huh,  well I can where that's going in some way.