What is the primary reason for using hydraulics in machinery?

Hydraulics are primarily used in machinery to increase strength. This is due to the principle of Pascal's law, which states that when pressure is applied to a confined fluid, the pressure change occurs throughout the fluid in all directions. As a result, hydraulic systems can harness a relatively small amount of force applied to a small piston to generate a much larger force on a larger piston. This amplification of force makes hydraulic systems particularly useful in applications requiring heavy lifting or significant force, such as in construction equipment, industrial machinery, and automotive lifts.

The other options, while they may have relevance in specific contexts, do not capture the primary application of hydraulics. For instance, while hydraulics can contribute to efficiency in some situations, their main feature is not efficiency but rather the ability to multiply force. Similarly, speed is not a primary benefit of hydraulics; in fact, hydraulic systems can sometimes operate more slowly than mechanical systems. The use of hydraulics does not inherently increase weight, as the systems are designed to be as lightweight as possible while still achieving their strength advantages.