Which term would describe a device that would run forever without energy input, violating a fundamental law?

• A. Thermonuclear Energy
• B. Perpetual Motion Machines
• C. Mechanical Energy
• D. Open System

Answer: (B)

A perpetual motion machine describes a device that would run forever without any energy input. That idea clashes with the laws of thermodynamics, because energy cannot be created from nothing and must come from somewhere. In reality, every real machine loses energy to friction, heat, and other inefficiencies, so it cannot keep going indefinitely without some energy entering the system.

The other terms don’t fit this concept: thermonuclear energy refers to energy released by nuclear fusion, not a machine that runs on its own; mechanical energy is just a form of energy an object has, not a description of a self-sustaining device; an open system is one that exchanges energy or matter with its surroundings, which doesn’t inherently imply eternal motion without input.