Which of the following is true about hydraulic cylinders?

Hydraulic cylinders are mechanical devices used to produce linear motion and force by using hydraulic fluid. The statement that they operate under pressure using liquid accurately captures the fundamental principle of how hydraulic systems work. When hydraulic fluid is pumped into the cylinder, it creates pressure that pushes the cylinder’s piston, resulting in movement. This capability is what allows hydraulic cylinders to perform various tasks in construction equipment, industrial machines, and automotive applications.

The other statements do not align with the characteristics of hydraulic cylinders. For example, they can be utilized in both static and dynamic applications, depending on design and configuration. They do not provide continuous torque; instead, they generate linear force. Additionally, while hydraulic systems generally require maintenance to ensure proper function and to prevent leaks or mechanical failures, they cannot be considered maintenance-free.