Which device converts hydraulic pressure into rotary mechanical motion?

The correct choice is a hydraulic motor, as it is specifically designed to convert hydraulic pressure into rotary mechanical motion. When hydraulic fluid is directed into the motor, it activates the internal mechanism, creating rotational movement. This process allows hydraulic motors to power various machinery and equipment that require rotational force, making them integral in many applications, such as in aircraft systems or industrial machinery.

In contrast, a hydraulic pump is responsible for generating hydraulic pressure by moving the fluid, rather than converting pressure into motion. A hydraulic cylinder transforms hydraulic pressure into linear motion rather than rotary motion, while a hydraulic accumulator serves to store hydraulic energy by holding pressurized fluid, which can be released as needed but does not generate motion on its own. Each of these components plays a crucial role in hydraulic systems, but the hydraulic motor uniquely fulfills the function of translating hydraulic pressure into rotary movement.