

Is Perpetual Motion in a Vacuum Possible? - ankeshk

I'm no scientist.  But I have an amateurish interest in reading about perpetual motion machines.<p>Here is a thought I had.  I am sure it won't work.  But can you tell me why?<p>1. In a vacuum - if you push something, it'll keep on moving because of lack of friction / law of inertia - correct?<p>2. So can you push a rotor in a vacuum so that it always keeps on moving on its hinges and keeps on generating electrical power - which can be stored in batteries?
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ThomPete
The problem is not actually the motion but the generation of energy. I.e. you
need to create more than you consume. And you can't create unless you consume.

So even if you could make it go around perpetually you wouldn't generate
energy just from that.

It's kind of like lighting a match.

You can sway it around in the air, but it is not until you actually put it
down on the match box that you start creating energy.

Now the trick is to create energy to both keep dragging your match along the
box and at the same time generation som energy surplus.

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bdfh42
Entropy will always get you baby...

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ankeshk
Thanks for the comment.

Pardon my ignorance.

I read about entropy on wikipedia. But didn't get a clear picture about it.

Does it mean that because of entropy - the rotor in a vacuum will stop
movement?

(What I'm curious about is: "A thing in motion keeps on moving at the same
speed in a vacuum" - is that an incorrect statement?)

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bdfh42
A thing in motion will continue at the same speed and in the same direction
until another force acts upon it.

OK - you have spotted that drag from air can quickly slow down an object here
on earth and that thus an object in a vacuum will spin (or whatever) for a lot
longer without air slowing it down.

But drag from air is not the only force likely to affect the motion of your
theoretical object.

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nopassrecover
The problem as I understand it is this. Let's imagine that the rotor spins
forever. At some stage that rotor has to be attached to something else to
actually harness the energy and here some friction will occur.

