Two pistons in a hydraulic system have areas 1 cm² and 50 cm². For a load of 500 N on the large piston, the required force on the small piston is 10 N. If the small piston moves down by 50 cm, the large piston moves up by:

Since the same volume of fluid must pass every cross-section per second (continuity), the fluid speeds up where the pipe narrows; Bernoulli's equation then says this faster-moving fluid has lower pressure - the principle behind a venturi meter and an aircraft wing's lift.