What type of machines consist of only one or two parts?

The correct answer is found in the classification of machines based on their complexity and functionality. Simple machines are basic mechanical devices that typically consist of one or two parts designed to alter the direction or magnitude of a force. Common examples of simple machines include levers, pulleys, inclined planes, wheels and axles, screws, and wedges. They serve to make work easier by allowing forces to be applied in a more convenient manner.

The focus on simplicity highlights their fundamental role in mechanics, where they perform work with minimal components, making them foundational to mechanical engineering and physics. In contrast, terms like complex machines and advanced machines refer to systems that incorporate multiple components and sophisticated mechanisms, while hybrid machines may combine elements of different types of machines, including both simple and more intricate designs. Understanding this hierarchy helps clarify why simple machines are characterized by their fundamental simplicity and ability to perform tasks efficiently using limited parts.