Pascal's Law:

According to this law, "while pressure is applied anywhere on the surface of an enclosed liquid at rest, an equal and uniform pressure is transmitted over the whole liquid; the pressure is transmitted throughout the liquid and acts in a direction at right angles to the surface of the liquid everywhere".

Pascal's law can be demonstrated by taking a spherical flask filled with water and fitted with a piston (Figur7). As shown in the figure, the flask has a number of small holes all around its circular surface. While the piston is gradually pushed-in, the water spreads out by different holes at almost the same speed.

Figure: Demonstration of Pascal's Law

Pascal's law has been put to a variety of uses in our everyday life. Some of the machines which operate on Pascal's law are the hydraulic press used to compress metal steels, wool and etc., a hydraulic brakes used in cars, aircrafts etc., and the hydraulic jack used to lift vehicles in workshops. These machines are collectively referred to as hydraulic machines. Let us discuss the working of one of these hydraulic machines.