What is the primary function of gears in machinery?

Gears are essential components in machinery primarily because they are designed to change the speed and direction of motion. When gears are interlocked, the rotation of one gear drives the next, allowing for a precise control of mechanical advantage. By altering the size of gears in relation to each other, various speed outputs can be achieved; smaller gears rotate faster than larger ones, effectively increasing speed, while larger gears can provide more torque at slower speeds.

Additionally, gears can change the direction of motion. For example, in a simple gear train, the rotation of an input gear can result in an output gear that rotates in a different direction. This property is crucial in various applications, such as in automobiles where the gear system allows the wheels to rotate while the engine operates in a different rotational plane.

The other options, while they have their functions in different contexts, do not capture the primary role of gears. Storing energy is characteristic of springs or flywheels, cooling moving parts pertains to lubrication systems, and providing a foundation relates more to the structural integrity of machinery rather than the function of gears themselves.