Why can't you bid on a perpetual-motion machine?

Why can't you bid on a perpetual-motion machine?

• A. The First Law of Thermodynamics prohibits creating energy.
• B. The Second Law says energy loss due to entropy prevents perpetual motion.
• C. The Zeroth Law prohibits perpetual motion.
• D. The Third Law prohibits perpetual motion.

Answer: (B)

The main idea here is the Second Law of Thermodynamics: in any real process, some energy becomes unavailable as disorder, and you can’t convert all heat into work. Real devices have irreversibilities like friction and air resistance, so they lose energy as heat and can’t run forever without input. To keep a machine going, you’d have to supply that lost energy back, which defeats the idea of perpetual motion. So perpetual motion isn’t possible because you can’t achieve 100% efficient energy conversion in practice. The First Law says energy isn’t created or destroyed, but that doesn’t by itself forbid a machine from running indefinitely; it just means you’d have to supply energy for losses anyway. The Zeroth and Third Laws aren’t the reasons here—thermal equilibrium and absolute-zero considerations don’t directly prevent perpetual motion.

The main idea here is the Second Law of Thermodynamics: in any real process, some energy becomes unavailable as disorder, and you can’t convert all heat into work. Real devices have irreversibilities like friction and air resistance, so they lose energy as heat and can’t run forever without input. To keep a machine going, you’d have to supply that lost energy back, which defeats the idea of perpetual motion. So perpetual motion isn’t possible because you can’t achieve 100% efficient energy conversion in practice.

The First Law says energy isn’t created or destroyed, but that doesn’t by itself forbid a machine from running indefinitely; it just means you’d have to supply energy for losses anyway. The Zeroth and Third Laws aren’t the reasons here—thermal equilibrium and absolute-zero considerations don’t directly prevent perpetual motion.