If you wanted to learn about perpetual motion and alternative energy what category is that?

[Marshalscienceguy]

Perpetual motion machines are devices which keep going on their own that never stop. They have several different kind. I was thinking it might fall under mechanics but is this correct? People have been looking into these alternative means of energy for a lot time. However no one has ever created a perfect machine. So exactly what category of science would this fall under?

Edited January 22, 2014 by Marshalscienceguy

[Endercreeper01]

Speculations. Perpetual motion is impossible in a closed system.

[studiot]

 

Perpetual motion is impossible in a closed system.

 

 

Careful,

 

Perpetual motion machines are impossible.........

 

But see Newton's First Law

 

Perpetual motion is possible in an appropriate system.

Edited January 22, 2014 by studiot

[Greg H.]

 

People have been looking into these alternative means of energy for a lot time. However no one has ever created a perfect machine.

 

Mostly because it's impossible to do.

[ACG52]

 

Perpetual motion machines are devices which keep going on their own that never stop. They have several different kind. I was thinking it might fall under mechanics but is this correct? People have been looking into these alternative means of energy for a lot time. However no one has ever created a perfect machine. So exactly what category of science would this fall under?

 

Fantasy.

[Acme]

Pseudoscience is the appropriate category for learning about perpetual motion machines. Alternative energy is the appropriate category for learning about alternative energy machines and systems.

[Didymus]

Indeedy. No machine can be perpetual... Even without thermodynamics, the machine will rust and degrade eventually.

 

Perpetual motion is all around us... For an example, see any object moving through space. Without a resistance, it will travel forever, without slowing.

 

On to the more theoretical stuff: while perpetual machines are impossible, there are great sources of energy not currently in use that have fabulous potential. Stick a 10 pound magnet on the bottom of a table and you can observe it actively applying at least 10 pounds of pressure for as long as it remains magnetized. The challenge is finding a way to generate electricity using the energy already stored in that magnet.

 

For truly perpetual energy: see gravity.

[swansont]

On to the more theoretical stuff: while perpetual machines are impossible, there are great sources of energy not currently in use that have fabulous potential. Stick a 10 pound magnet on the bottom of a table and you can observe it actively applying at least 10 pounds of pressure for as long as it remains magnetized. The challenge is finding a way to generate electricity using the energy already stored in that magnet.

Mistaking force for energy is what creates the windmills that the perpetual motion crowd tilts after. Something that is not moving isn't using up an energy to remain there. That it is, and could be tapped into, is an illusion created by this misunderstanding.

[Didymus]

It's a matter of definition. A helicopter sitting on the ground without moving experiences the constant force of gravity and isn't moving because it's already at rest on the ground. That same helicopter hovering in one spot above the ground has a velocity of zero. The rotors and engine is doing quite a lot, but there is no net motion (relative to the ground), yet there is quite a bit of energy needed to overcome the constant force of gravity.

 

Likewise, magnetic and radioactive materials have quite a bit of energy stored within them. Not perpetual, but quite a lot. A bit of uranium sitting on a shelf still has harvestable energy, even if the uranium is stationary.

 

No one suggested that gravitational or magnetic energy is "used up" when it's utilized.

[swansont]

It's a matter of definition. A helicopter sitting on the ground without moving experiences the constant force of gravity and isn't moving because it's already at rest on the ground. That same helicopter hovering in one spot above the ground has a velocity of zero. The rotors and engine is doing quite a lot, but there is no net motion (relative to the ground), yet there is quite a bit of energy needed to overcome the constant force of gravity.

 

Likewise, magnetic and radioactive materials have quite a bit of energy stored within them. Not perpetual, but quite a lot. A bit of uranium sitting on a shelf still has harvestable energy, even if the uranium is stationary.

 

No one suggested that gravitational or magnetic energy is "used up" when it's utilized.

 

As I was responding to a specific example, it's not hard to take what I said out of context, move the goalposts, and come up with some counterexamples.

 

If the challenge is to tap into magnetic energy with no motion, and yet not use it up, that truly would be creating energy. Not going to happen.

[Didymus]

My point exactly. One can observe a minimum of 10 pounds of force being constantly applied if a 10 pound magnet sticks to the underside of a table. Obviously to do any work either the magnet has to move across wires or wires have to move across a magnetic field. Just like uranium doesn't just generate electricity sitting on a table. You have to harness it by putting it close enough to water to boil, pushing turbines, rotating wires around a magnetic field and pushing those electrons.

Likewise, with magnets. Create a magnetic pressure differential so that an array of magnets on a shaft constantly goes toward poles it can never reach to yield rotation. Then convert axial kinetic energy to electricity and win.

Edited January 28, 2014 by Didymus

[swansont]

Obviously to do any work either the magnet has to move across wires or wires have to move across a magnetic field.

 

And requires external work for that to happen, or the system come to rest. Any energy output comes from that external work, not from the magnet.

[studiot]

 

The rotors and engine is doing quite a lot, but there is no net motion (relative to the ground), yet there is quite a bit of energy needed to overcome the constant force of gravity.

 

 

 

 

Gravity is not the source of the energy, that is external to the helicopter-gravity system.

 

The only energy you can get out of the helicopter-gravity system is the potential energy available when the helicopter descends.

 

You can only do this once, unless you input further energy from an external source.

 

Gravity is not an inexaustible source of energy.

[swansont]

A hovering helicopter isn't a stationary system, anyway. The rotors are moving, as is the air. Plenty of identifiable work being done to account for the energy being used.