Hydraulic brakes used in automobiles work on which principle?

The correct answer is B, Pascal's law. Pascal's law states that pressure applied to an enclosed fluid is transmitted undiminished in every direction to all parts of the fluid and to the walls of the container. In a hydraulic brake a small force on the narrow master piston creates a pressure that reaches the wider pistons at the wheels, where the same pressure over a larger area gives a much larger force, and all wheels are braked equally at the same moment.

Option A, Archimedes' principle, deals with the upward buoyant force on a body immersed in a fluid and explains ships, submarines and the lactometer. Option C, Bernoulli's principle, relates the speed of a flowing fluid to its pressure and explains the lift of an aerofoil and the working of an atomiser. Option D, Newton's law of gravitation, concerns the attraction between masses. The hydraulic lift and the hydraulic press are the other two standard applications of Pascal's law.