Hydraulic systems (like a car's brakes) work based on the principle that:

HYDRAULIC SYSTEMS work on PASCAL'S PRINCIPLE: pressure applied to a confined (enclosed) liquid is transmitted EQUALLY throughout the liquid in all directions. ASVAB Mechanical Comprehension tests hydraulics. Because liquids are nearly INCOMPRESSIBLE, force applied at one point (a small piston) is transmitted through the fluid to another point (a larger piston), and can be multiplied — a small force on a small piston creates a large force on a large piston (hydraulic advantage). Car brakes and hydraulic jacks use this. Pascal's principle of equal pressure transmission is commonly tested.