## Applications:Pascal’s law for transmission of fluid pressure

Hydraulic lift:-

• Hydraulic lift is a lift which makes use of a fluid.
• For example: Hydraulic lifts that are used in car service stations to lift the cars.
• Principle: –
• Inside a hydraulic lift there are 2 platforms,one has a smaller area and the other one has a larger area.
• It is a tube like structure which is filled with uniform fluid.
• There are 2 pistons (P1 and P2)which are attached at both the ends of the tube.
• Cross-sectional area of piston P1 is A1 and of piston P2 is A2.
• If we apply force F1 on P1, pressure gets exerted and according to Pascal’s law the pressure gets transmitted in all the directions and same pressure gets exerted on the other end.As a result the Piston P2 moves upwards.
• Advantage of using hydraulic lift is that by applying small force on the small area we are able to generate a larger force.
• Mathematically:- F2=PA2
• where F2 = Resultant Force,A2 = area of cross-section
• F2= (F1/A1)A2 where P=F1/A1 (Pressure P is due to force Fon the area A1)
• F2 =(A2/A1)F1. This shows that the applied force has increased by A2/A1.
• Because of Pascal’s law the input gets magnified.  The above figure shows the internal structure of the hydraulic lift.

### Hydraulic Brakes

• Hydraulic brakes work on the principle of Pascal’s law.
• According to this law whenever pressure is applied on a fluid it travels uniformly in all the directions.
• Therefore when we apply force on a small piston, pressure gets created which is transmitted through the fluid to a larger piston. As a result of this larger force,uniformbrakingis applied on all four wheels.
• As braking force is generateddue to hydraulic pressure,theyare known as hydraulic brakes.
• Liquids are used instead of gas as liquids are incompressible.

Construction

• The fluid in the hydraulic brake is known as brake fluid.
• It consists of a master cylinder, four wheel cylinders and pipes carrying brake fluid from master cylinder to wheel cylinders.
• Master cylinder consists of a piston which is connected to pedal through connecting rod.
• The wheel cylinders consist of two pistons between which fluid is filled.
• Each wheel brake consists of a cylinder brake drum. This drum is mounted on the inner side of wheel. The drum revolves with the wheel.
• Two brake shoes whichare mounted inside the drum remain stationary.

Working

• When we press the brake pedal, piston in the master cylinder forces the brake fluid through a linkage.
• As a result pressure increases and gets transmitted to all the pipes and to all the wheel cylinders according to Pascal’s law.
• Because of this pressure,both the pistons move outand transmit the braking force on all the wheels. 