Magnets to create Perpetual Motions Machines, Why is it Impossible?

[zfactor]

Will it gladden you to know that it does?

Yes.

But you would fall straight though the water and die. Sorry!

Really? You wouldn't float like in a normal pool? I mean, I can see how you could swim out of the bottom, but still. Speaking of, might it be possible to stick your head out of the bottom for air?

I suppose you could constantly tread water, but that's not something I would do...

And sticking your head out would break the surface tension of the water (which keeps the water from falling, helped along by the suction) causing you to fall and die...

 

[Dana22]

I only have a 12th grade level of physics education so keep that in mind. I was thinking about how energy cannot be created, and how magnets seem to break this rule.

If a bigger magnet pulls a metal object, it has done work on the object. But did the big magnet "lose" some of its magnetic power? No, right? So doesn't that mean magnets can do work forever (or until they wear out, if they do)?

Anyone who's a physics nut care to explain why we haven't gotten something like this invented yet? Using magnets to spin something would create friction in some way or another, but if the only loss of energy is through friction would it mean tis pretty damn efficient? And for all intents and and purposes is a very good machine for making energy?

I guess the problem is keeping the metal object from reaching the magnet, since then the "energy" will stop?

http://knowyourmeme.com/memes/troll-sciencetroll-physics

I think that about sums it up. IT'S TOO DAMN SIMPLE. And awesome.

OT: friction can be a *****.

Lol. This troll science stuff is pretty funny.

but...

Why doesn't this work?

Because surface tension doesnt work in macro scale.

 

[DigitalSushi]

I've always wondered this, I reckon we can get a giant dynamo going that goes along the earth using the North and South pole to power itself, so we'd have a giant magnet spanning the length of the Atlantic.

Two problems with this,
Firstly, while its a totally viable project because I thought of it while drunk the heat output would be shockingly difficult to manage, even with coolermaster on the project or Dr Freeze as the head technician.

Secondly, by virtue of being a giant fucking magnet kids with braces would fly towards the Atlantic, and the parent's wouldn't be able to retrieve them until they had perfect teeth.

edit: not to mention my cutlery, I need that for eating, no way I'm eating with plastic forks.

 

[zfactor]

Because surface tension doesnt work in macro scale.

Uh, yes it does.

How do you explain those bugs that crawl on the top of lakes (by using sirface tension)? I'd say that's macro scale.

The problem is the weight (force from gravity) of the water overcomes surface tension. So if you used suction to oppose that force and cause the net down force to be less than the maximum sufrace tension force, BAM floating water.

 

[psivamp]

Perpetual motion is possible in the form of objects in orbit due to gravitational pull in a frictionless environment (i.e. planets orbiting the sun), or objects spinning in a frictionless environment (i.e. planets rotating in space). The problem is that as soon as you lose any energy, to anything, you are doomed to failure.

Apparently, the moon is actually going to escape our orbit eventually.

 

[znix]

Nothing is impossible in a Universe that supposedly started from a speck of nothing and expanded into something that is incomprehensibly large and full of things we have barely started to imagine.

The Earth moves through the Universe at very high speed. This can be harnessed, somehow. Gravity can be harnessed, somehow. Coriolis effect can be harnessed, somehow. The properties of various materials can be exploited as can the very structure of reality on a quantum level.

The problem with a perpetual motion machine, I think, is not to make one. It's possible, somehow. The question is more that it'll be impossible to verify that it truly is a perpetual motion machine, without letting it run for an eternity.

Perhaps a quantum state could be excited to spontaneously swing back and forth forever. That would be a perpetual motion machine, but verifying that it will stay that way is tricky.

The Universe is constantly evolving and so the most we can hope for is to create something which is valid for a brief moment in its evolution. Eventually the nature of the Universe will have changed and so will the "rules" that govern it. It changed as it grew out of nothing and it may change in ways we cannot forsee at this point. After all, we have very limited experience with the Universe, despite liking to think we know it all

Physics is a respected field, but people often put on their "THERE ARE LIMITS!" glasses and refuse to think outside the box. Most forget to dream and think big, relegating that kind of thing to folks who "should get an education."

If you can dream it, there is SOME way of doing it. It may not be an obvious way, it may not be possible in your life time, but anything, any arrangement of atoms and their core elements, can be made. Even the properties governing these things will eventually be brought fully under control, as long as people press on.

We, as a race, may end up killing each other through war or irresponsibility with our planet, but that's beside the point

 

[psivamp]

Because surface tension doesnt work in macro scale.

Uh, yes it does.

How do you explain those bugs that crawl on the top of lakes (by using sirface tension)? I'd say that's macro scale.

The problem is the weight (force from gravity) of the water overcomes surface tension. So if you used suction to oppose that force and cause the net down force to be less than the maximum sufrace tension force, BAM floating water.

The magnitude of surface tension is such that it will not scale up to applications of this magnitude. Bugs walking on the surface of water due to surface tension is of the same scale as the straw example.
You can fill a Mason jar with water, then cover the lid with a mesh and it will not flow out when upended as long as it is not disturbed. If the surface tension is broken anywhere, the water all flows out. If you tip the Mason jar, the balance of forces is upset and the water all runs out. That is with a vacuum. If you can't keep water in a handheld jar with a vacuum, there's no way you can keep it in a pool against the force of gravity.

 

[DiMono]

Though not perpetual motion, here's a really cool magnet motor. I've read that its usefulness breaks down rapidly when you try to do something with the energy it generates [http://www.nuscam.com/perendev.htm], but I think it would be awesome to build one of these just to have:


It's called a Perendev Motor. And I want one.

 

[Folio]

Tie a cat to a piece of buttered toast.

Butter always fals butter side down. Cat's always land on their feet.

Drop bound cat from a high place. Perpetual motion, zero gravity.

 

[Ryhzuo]

If a bigger magnet pulls a metal object, it has done work on the object. But did the big magnet "lose" some of its magnetic power? No, right? So doesn't that mean magnets can do work forever (or until they wear out, if they do)?

The solution to this is actually very simple. A object has potential energy based on it's position in a field of any kind. Just like say a ball would have gravitational potential energy if you lift it above the ground, a metal object will have magnetic potential energy if you position it within in a magnetic field. Conservation of energy still exists because the potential for any object experiencing an attractive force is 0 at distance infinity, and NEGATIVE for any distance closer than that. Yes, a ball 5 meters above the ground actually has negative potential energy.

So basically, any kinetic energy an object gains in a magnetic field has negative potential energy based on that field, equal to the modulus of the kinetic, or any other form of energy created as result of the movement of that metal in the field, and hence there is a conservation of energy, no energy is actually 'made'.

Hope that helps.

 

[Unesh52]

Because surface tension doesnt work in macro scale.

Oh yeah, there's that whole "strength rises by the cube of size" or whatever it is...

Sad

 

[Withall]

And, the -ultimate- problem with any perpetual motion machine is the fact that -everything- suffers from molecular decay. -That- is what makes the "perpetual" part just a tad impossible.

Any and all other physical laws that has already been presented are correct, true. Still. Everything decays. Halt entropy, and you prevent molecular degeneration.

While dealing with abstract physical issues.... is "Heat Death" really possible?

 

[Eclectic Dreck]

There is a common perception that perpetual motion is impossible. This is not true. The actual problem is that there is no such thing as a perpetual motion device that does work.

If there were no forces acting against an object in motion, it will stay in motion perpetually. If you apply a force against this object (and thus do work (expend energy)), the object's motion will change. If you apply this force directly against the motion of the object, the only way to resist slowing down is to oppose this object with a second force (and thus expend energy).

Basically, the problem is that if you want a machine to interact with anything in any meaningful way the energy in the system will change. The real life application here is that there is no perfectly efficient thermal exchange engine. The closer you get to a perfect exchange, the more energy efficient the engine becomes. Like many rules in physics, you can approach perfection but it appears that reaching it is impossible.

 

[Quaxar]

There is a common perception that perpetual motion is impossible. This is not true. The actual problem is that there is no such thing as a perpetual motion device that does work.

Excuse me, but I last time I checked the second law of Thermodynamics still stated that perpetual motion machines are impossible.
You want to argue with Sir Isaac Newton?

 

[Mr.Mattress]

While we're on the subject of "Why can't this work in Science", I simply have to ask:

How the heck does this not work?! Is the magnet too small? Someone has to explain this too me, cause I suck at science.

 

[Eclectic Dreck]

There is a common perception that perpetual motion is impossible. This is not true. The actual problem is that there is no such thing as a perpetual motion device that does work.

Excuse me, but I last time I checked the second law of Thermodynamics still stated that perpetual motion machines are impossible.
You want to argue with Sir Isaac Newton?

The law explicitly states: "In any process in an isolated system, the total energy remains the same.".

This means exactly what it says - if the system is isolated from outside interference of any sort, the total energy in the system remains the same.

Take for example a simple pendulum system consisting of an ideal (massless) rod and an ideal mass (a mass point) attached to the rod some length away. The rod is attached to an ideal (frictionless) pivot. This system will include a second ideal mass point some distance away from the pendulum. If you do nothing at all, the pendulum will simply remain at rest. If you introduce energy into the system by moving the pendulum such that it moves away from the other mass point (and thereafter never interact with it again), the pendulum will oscillate back and forth indefinitely across the same arc.

This (common) simple physics problem has been impossible to replicate in reality. So, what's the problem? Well, it turns out that isolating the system itself is the problem. You see, the pivot point will never be frictionless, and as such the simple action of motion will be resisted by friction and energy will be lost in the form of heat (entropy). If you conduct this experiment without the benefit of a perfect vacuum, you will also find that moving an object through a fluid (the air) will also result in friction and again the system loses kinetic energy/potential energy to heat.

The problem is one of isolation. The better statement is that it is impossible to produce a perpetual motion device that does work (of any sort) indefinitely because some energy is always going to be lost to entropy. This is what I mean by thermal efficiency. Creating something that moves perpetually is not impossible - you'll find the second law of motion tells us about inertia and points out that an object in motion will stay in motion in the same direction and at the same velocity unless acted upon by an outside force. Here again, the problem is isolation.

To put that another way, the second law simply states that a system in isolation will only have a change in energy if acted upon by an outside force. Thus, if a perpetual motion system is doing work outside of the system, energy is lost. If no energy replaces it, it would eventually stop moving. What the law says is impossible is simple: that any change in energy in a system must come from outside interference. Thus it is better known as the law of conservation of energy.

 

[Eclectic Dreck]

While we're on the subject of "Why can't this work in Science", I simply have to ask:

How the heck does this not work?! Is the magnet too small? Someone has to explain this too me, cause I suck at science.

There is a force that is exerted between the magnet and the anvil yes, but they are in perfect opposition. The force the magnet applies to the anvil is opposed (the magnet is trying to move closer to the anvil) by the apparatus holding the magnet to the cart. The anvil also wants to move closer to the magnet but is opposed by the cart itself.

Basically, if you just draw the logical force directions, you'll find that eventually the forces meet in perfect opposition and thus you do not move. This same basic fact is also why you cannot pick yourself up by simply grabbing your boots and pulling. For that to happen, you have to apply a force outside the system to the system, otherwise the total kinetic energy of the system will remain the same.

Were you to secure that same magnet at the same distance to an object that was not attached to the cart, then it might move if the force was sufficient to overcome the static friction and whatnot. This is because the force acting upon the cart (the system) is coming from outside the cart (i.e. it is coming from outside the system).

 

[Quaxar]

snip

Damn, I didn't expect such a wall of text... err, I'll return to you tomorrow evening with appropriate arguments since I've got to get up early for work and really need to catch some sleep beforehand.

 

[Mr.Mattress]

While we're on the subject of "Why can't this work in Science", I simply have to ask:

How the heck does this not work?! Is the magnet too small? Someone has to explain this too me, cause I suck at science.

There is a force that is exerted between the magnet and the anvil yes, but they are in perfect opposition. The force the magnet applies to the anvil is opposed (the magnet is trying to move closer to the anvil) by the apparatus holding the magnet to the cart. The anvil also wants to move closer to the magnet but is opposed by the cart itself.

Basically, if you just draw the logical force directions, you'll find that eventually the forces meet in perfect opposition and thus you do not move. This same basic fact is also why you cannot pick yourself up by simply grabbing your boots and pulling. For that to happen, you have to apply a force outside the system to the system, otherwise the total kinetic energy of the system will remain the same.

Were you to secure that same magnet at the same distance to an object that was not attached to the cart, then it might move if the force was sufficient to overcome the static friction and whatnot. This is because the force acting upon the cart (the system) is coming from outside the cart (i.e. it is coming from outside the system).

Oh okay, thanks for clearing that up for me. What I basically read is this: The fact that both of them are stuck keeps them from moving the cart. That actually makes sense. However, does that mean if I were to make a car basically like that but where I could make the anvil move back and fourth repeatedly, would that make it move?