Why, according to the laws of physics, is it impossible to build a perpetual motion machine?

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A perpetual motion machine is a machine that could theoretically do work forever, without any energy input. Although spectacular in theory, this type of machine is not possible due to the Laws of Thermodynamics.

According to the First Law of Thermodynamics, energy cannot be created or destroyed, it can only...

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A perpetual motion machine is a machine that could theoretically do work forever, without any energy input. Although spectacular in theory, this type of machine is not possible due to the Laws of Thermodynamics.

According to the First Law of Thermodynamics, energy cannot be created or destroyed, it can only be changed to a different form or transferred. Stores of energy for machines are finite, and are used over time and lost due to work done as well as dissipated by phenomena such as friction, air resistance, electrical resistance, etc. The energy store would then need to be filled with more energy, which would need to be transferred. For a perpetual motion machine, this energy would have to be re-created, and it cannot be created because of the First Law of Thermodynamics.

Perpetual motion machines would only be possible if a substance could be found that generated more energy than it used. And what we know right now is that no such substance exists. Some sort of energy input is needed in all machines, and no machine can do work indefinitely without an energy source.

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