Which statement best describes the difference between a hydraulic cylinder and a hydraulic motor?

Which statement best describes the difference between a hydraulic cylinder and a hydraulic motor?

• A. A cylinder provides linear motion and consumes oil only while moving; a motor provides rotary motion and consumes oil continuously
• B. A cylinder provides rotary motion and consumes oil continuously; a motor provides linear motion and consumes oil only while moving
• C. A cylinder and a motor both provide linear motion
• D. A cylinder and a motor both provide rotary motion

Answer: (A)

The key idea is how each actuator converts fluid power into motion and how that power is used.

A hydraulic cylinder turns hydraulic energy into linear, back-and-forth motion along the piston rod. It uses pressurized fluid to move, and once the piston reaches its position and the flow is stopped by the control valve, there’s little or no flow needed to hold it in place (aside from leakage). So energy is consumed mainly while the cylinder is moving.

A hydraulic motor, on the other hand, converts fluid power into rotational motion. To keep turning, the motor requires a continuous supply of pressurized fluid, overcoming load and friction, so the flow is ongoing during operation.

Thus, the description that a cylinder provides linear motion and uses oil only while moving, while a motor provides rotary motion and uses oil continuously, best captures the fundamental difference. The other statements misstate the type of motion or imply both actuators behave the same way.