Pascal’s Law states that the pressure applied to a fluid in a closed container is transmitted equally to all points in the fluid and act in all directions of the container. Pascal’s Law is applicable to both solids and liquids.
The law was proposed by Blaise Pascal, a French Physicist and Mathematician. He observed that when a fluid is at rest, the same amount of pressure is applied at all the points which are at the same height. Now, we get to know that pressure is not a vector quantity; and, therefore, it can not be assigned any direction. If we begin to consider that fluid is a horizontal bar with a uniform cross-section and it is in a state of equilibrium, then there will be an equal and balanced force which will be exerted at the two ends. However, if we consider that an unequal force is acting on the horizontal bar, in that case, the liquid will have some net force acting on it and it will flow. Therefore, it can rightly be said that since the liquid does not flow, it definitely has equal pressure acting on it at all the points.
The mathematical representation of the law is as follows:
F = PA; where F=applied force, P=pressure transmitted, and A=cross-sectional area.
Let us have a look at some of the examples of Pascal’s Law:
1. Hydraulic Lift
A hydraulic lift is versatile in its utility. It has a hydraulic apparatus which is used to lift heavy objects. In the case of hydraulic lifts, force applied creates “lift” and “work.”
It is based on the principle of equal pressure transmission throughout the fluid. A narrow cylinder (A) is connected to a wider cylinder (B) fitted with airtight pistons filled with an incompressible fluid. The mathematical representation of the Pascal’s Law helps in the determination of pressure which can be exerted on the fluid in the piston so as to create enough force for lifting and moving an object.
When pressure from piston A is transmitted to piston B, piston B lifts the heavy object like big machines, vehicles. The hydraulic lift technology has widespread applications in the industrial, construction, transport sector, etc.
2. Hydraulic Jack
Hydraulic jacks, which come under the category of a closed container, follow the principle of Pascal’s Law. They are used to lift heavy bodies.
The hydraulic jack consists of two cylinders, a larger and a smaller one; and these two cylinders are connected. When its handle is pressed down, a valve closes and the small piston forces the fluid through another valve to a larger cylinder which, then, produces a large force to be transmitted to the load. Therefore, we can say that when force is applied, the pressure is exerted throughout the volume and surface of the cylinder.
The handle is moved up and down repeatedly until the load is sufficiently lifted up by the hydraulic fluid flowing buffer tank to the small cylinder. Hydraulic jacks are highly advantageous in the automotive industry and are often used to lift cars above the ground level for repair and maintenance.
3. Hydraulic Brakes
One of the most common examples of Pascal’s Law is the hydraulic braking system present in the automobiles. Every time you see a car come to a halt, the principle of Pascal’s Law comes into action.
A number of components form the braking system in cars. When force is applied on the brake pedal, there is a movement of the piston and rod in the master cylinder. A liquid which is known as brake or hydraulic fluid, enclosed in the container, is used to transmit the pressure from the brake pedal to the wheels of the vehicle against the brake discs or brake drums. The frictional force between these force components causes the vehicle to stop. Hydraulic brakes are used in cars, motorcycles and lorries.
4. Hydraulic Pumps
Hydraulic pumps, which convert mechanical energy into hydraulic energy, facilitate the movement of a fluid, and here, yet again, Pascal’s Law comes into play.
Hydraulic pumps help in the discharge of fluid. It is equipped with a small cylinder connected to a large cylinder and both the cylinders are filled with oil. Compressed air introduced to the small cylinder exerts a pressure on the surface of the oil. This pressure is transmitted by the oil to the large cylinder where the pressure acts on a large piston to produce a force large enough to lift a car.
Hydraulic pumps are used widely in the automobile industry.
5. Aircraft Hydraulic System
Hydraulic power system not only helps in slowing down of aeroplanes on runways but also help in the management of the flaps, landing gear, and flight control surfaces.
An aircraft hydraulic system consists of three critical mechanical components and hydraulic fluid. Even a small amount of hydraulic fluid helps in transmitting a large amount of force. The hydraulic fluid in contact with the cylinders/pistons is at different pressure. The oil which is at a relatively higher pressure can be pumped to either side of the piston head. The selector valve helps in controlling the direction of the fluid.