Q.In a hydraulic lift, the input piston had surface area 30 cm² and the output piston has surface area of 1500 cm². If a force of 25 N is applied to the input piston, calculate weight on output piston. [Ans. 1250 N]

Pascal's law states that the pressure applied at any point of an enclosed fluid at rest is transmitted equally and undiminished to every other point of the fluid, and to the walls of its container, provided the effect of gravity is neglected — demonstrated experimentally with a multi-armed vessel of frictionless pistons of different areas, where the pressure works out identical at every piston regardless of its individual area.

This principle underlies two major practical machines. A hydraulic lift applies a small force $F_1$ on a small piston of area $A_1$, generating a pressure that is transmitted undiminished to a much larger piston of area $A_2$, producing there a much larger output force $F_2 = F_1(A_2/A_1)$ — enough to lift a heavy load using only a modest input force. Hydraulic brakes work identically: pressing a brake pedal pushes a small master-cylinder piston forward, and the resulting pressure is tran …