Which statement about hydraulic systems is true?

• A. Output force is proportional to pressure only
• B. Output force is inversely proportional to pressure
• C. Output force is proportional to piston area only
• D. Output force is proportional to both pressure and piston area

Answer: (D)

In hydraulic systems, the force you get from a piston comes from pressure acting over the piston’s area. The relationship is F = P × A, where F is the output force, P is the fluid pressure, and A is the piston area. Because the same fluid pressure is transmitted to all parts of the system (Pascal’s law), the output force on a given piston depends on both how high the pressure is and how large the piston is. If you increase the pressure, the force increases proportionally; if you use a larger piston, the force also increases proportionally. So the statement that output force is proportional to both pressure and piston area is the correct description. It isn’t just about pressure alone, nor about area alone—the force is the product of the two.