On earth we know that if we rotate a motor electrical energy is produced but dues to friction and absense of force the motor do not rotate continuously. But if we are in Space where friction is zero cant we rotate the motor blades initially with the help of batteries and then the motor goes on moving and generating its own powers for the satellite?

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    $\begingroup$ Friction is not zero in space. There’s no atmospheric friction, and there’s no drag on the ground for vehicles, but neither of those is the kind of friction you’re talking about here. And even if there were no friction, your motor would still slow down if you used it to generate power. $\endgroup$ – Mike Scott Oct 14 '18 at 7:13
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    $\begingroup$ I'm voting to close this question as off-topic because this is a straight physics question best suited to Physics SE. $\endgroup$ – StephenG Oct 14 '18 at 11:10
  • $\begingroup$ The three immutable laws of thermodynamics for people who don't like physics. First law: you cannot win. Second law: you cannot come even. Third law: you cannot quit the game. $\endgroup$ – AlexP Oct 14 '18 at 13:16
  • $\begingroup$ Could you state your level of education? You will get a lot of clever replies from people that know very much, but I don't know of you learn anything from them. I believe part if your issue might be that we are dealing with things that are invisible like magnetic fields, electric currents and so on. The idea of a force generated by friction is something you experience every day, electromagnetic stuff not so much. But in order to explain it well, it's important to know whether you are e.g. a 14 year old student or a 50 year old writer with a degree in psychology. $\endgroup$ – Raditz_35 Oct 14 '18 at 13:33
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    $\begingroup$ @JBH Just because practically everything is on topic here does not mean a question would not stand a better chance of good answers on a more appropriate SE. It would be great if people took the attitude that other SEs are friends, not enemies we need to prevent getting questions from us. $\endgroup$ – StephenG Oct 14 '18 at 16:41

As in Physics.SE, I'll give you the rule of thumb for questions like these.

If you think you've found a way to produce unlimited energy for free, you almost certainly have not.

There ain't no such thing as a free lunch.

Perpetual motion, energy for free, or faster-than-light travel - if you think you've worked it out, and you haven't been studying physics for 30 years, it's a safe bet that you have not.

To sum up: No. The motor (which, if you're running it 'backwards' to generate power, has become a generator) will slow down and stop once the energy used to set it spinning is consumed by the items drawing power.

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  • $\begingroup$ ... not to mention the friction and other losses internal to the mechanism of the generator (bearings, magnetic interactions, etc), $\endgroup$ – pojo-guy Oct 14 '18 at 7:42
  • $\begingroup$ Well, allowing the OP the benefit of the doubt, let's assume a near-perfect generator/flywheel setup. 90%+ recovery of input energy. But yes, lots of other little losses. $\endgroup$ – jdunlop Oct 14 '18 at 7:44

Removing Energy From a System Will Stop It

Something about generators that people generally don't understand is that once you begin actually drawing power from it the electrical resistance and electromagnetic effects begin to slow down the generator. This means the motor must work harder to input more energy into turning the generator to maintain the voltage. So yes, assuming you created a friction-less generator it would continue to spin for as long as you left it alone, but the moment you began drawing current from it you would rapidly slow and then stall it unless you input more energy to keep it spinning.

The amount of electrical energy that can be produced by a generator can never be more than the amount of energy used to make it spin. In fact, in even the most efficient design possible it will always be slightly less because no system is 100% efficient. Due to electrical resistance some of the electricity will be converted into thermal energy and you will end up with slightly less electricity than the amount of kinetic energy you input into the system to get it spinning. Trying to draw power from a free-spinning generator floating in space and expecting infinite energy is like pouring milk from a gallon container and expecting to get 2 gallons out of it. It is not physically possible to get more energy out of a mechanical system than what you have put into it.

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  • $\begingroup$ I am not a techie like all. I was just curious when I read about voyager 1. I read that in 2020 or the next yearit will close down all its funtions as the batteries are providing 4 watt less power each year. That is why I aske out of curiosity that if we had any chance to improve the battery with additional power. Ma be I was not aware of the thing that even if motors rotators move freely, there still is some resistance due go its own magnetic field. $\endgroup$ – user261772 Oct 17 '18 at 18:29

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