Question

Why perpetual motion machines don't work?

Answer 1

Perpetual motion machines — devices that can do work indefinitely without any external energy source .
A consequence of the law of conservation of energy is that a perpetual motion machine of the first kind cannot exist. That is to say, no system without an external energy supply can deliver an unlimited amount of energy to its surroundings.
This kind of machine is impossible, as it would violate the first or second law of thermodynamics.

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