What mechanical principle does a hydraulic motor rely on?

A hydraulic motor operates based on the principle of fluid pressure. When pressurized fluid enters the motor, it creates a force on the vanes or pistons, causing them to move. This movement is then translated into rotary motion, allowing the hydraulic motor to perform work. The efficiency and power of a hydraulic motor depend significantly on the pressure of the fluid used; the higher the pressure, the more force is generated.

The other options do not apply to hydraulic motors. Molecular friction refers to resistance encountered at a molecular level and does not directly contribute to the operation of hydraulic systems. Electromagnetic induction is related to the generation of electric currents in conductors and is not relevant to the fluid-driven mechanics of a hydraulic motor. Air density changes pertain to processes involving gases and are not applicable to how hydraulic motors function with liquids. Therefore, fluid pressure is the fundamental mechanical principle that governs the operation of hydraulic motors.