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Formulas, Sounds, Sample Questions + Discussion [LENGKAP]

In a subject of Natural Sciences or SCIENCE, especially in physics, you must often hear the term from Bernoulli's Law. Bernoulli's Law is often also used as a measuring tool to calculate pressure and mass in a flow in a water pipe.

Maybe some of you know about the usefulness and benefits of this one physical law but you also need to know how to calculate it. [19659003] And in this article will explain the Bernaulli law namely the Bernaulli law formula, the application of Bernoulli's law, and examples of questions and discussion of Bernoulli's law. Following is an explanation of Bernoulli's law.

Studying Bernoulli's Law

Bernoulli's Law states that an increase in fluid flow velocity will result in a decrease in fluid pressure simultaneously or a decrease in the potential energy of the fluid. Therefore, it can be concluded that pressure can decrease if the speed of fluid flow continues to increase.

Bernoulli's Law was created by a mathematician named Daniel Bernoulli and he came from Switzerland or the Netherlands. Where he first published this law in his book entitled Hydrodynamica . The book was also published in 1738. In that book Daniel Bernoulli wrote the theory of this law and made it Bernoulli's law. In this Bernoulli legal formula, Daniel uses a mathematical basis to make it.

And in Bernoulli's Law, there is a statement which is often used as a legal basis. The statement is also often mentioned with the sound of Bernoulli's Law.

The following is a sound from Bernoulli's Law that you should know:

  • Fluid has no viscosity (inviscid)
  • Laminar fluid flow or which has permanent properties and no vortex
  • There is no loss of energy caused by friction between the wall and the fluid
  • No heat energy is sent to the fluid, it is either a heat gain or loss
  • Fluids are incompressible (incompressible)
  • change in time or steady
  • There is no loss of energy caused by turbulence

Not only that, Bernoulli's Law also has principles in it that must be obeyed. The principle of Bernoulli's law is a term often used in fluid mechanics. The principle also explains that there is an increase in fluid which can cause a decrease in the flow pressure that is in the fluid flow.

Also Read: Hydrostatic Pressure Formula

The presumed legal principle is used today. this is the result of a simplification of Bernoulli's law equation. In the equation it can be clearly explained that the amount of energy at a point in the same flow path.

This principle has also been stated directly by scientists from the Netherlands, Daniel Bernoulli. In a Bernoulli legal principle, Daniel has also simplified that principle as a form of his equation, which is to apply to a fluid flow that is stranded and an incompressible flow.

In each form of the equation, Daniel also uses a different mathematical formula, below this is the full explanation.

1. An incompressible flow

In contrast to an incompressible flow, an incompressible fluid flow is a fluid flow that has characteristics such as the absence of a change in the magnitude of the mass density or density of a fluid in the flowing stream.

Example of material including in the incompressible fluid flow, such as emulsions, water, various oils, and so on. In a form of equality in fluid flow, this law also uses the formula as in the formula below:

 Bernoulli's Formula: Unmatched Flow

The equation also only applies to flows that are not compressed with the following assumptions:

  • No friction occurred
  • The flow is steady state

2. Compressed Flow

This compressed flow has characteristics such as a change in the amount of mass density or density of a fluid along its flow. Examples of materials that are also included in the compressed fluid flow are natural gas, air, etc.

In this equation, this law has been formulated mathematically. The following is the formula of Bernoulli's Law whose flow is compressed:

 Bernoulli's Formula: Compressed Flow

All have equal values ​​at each point along a current line. The equation in this law will also be used as a medium to be able to determine the rate of fluid by measuring its pressure. In this Bernoulli law several principles are commonly used.

The principle is made into a tool that can measure an equation of the continuity of the rate of fluid which when it is in a narrow place instead it will only get even bigger.

Also Read : Density Formula

Application of the Bernoulli Law

Below is an application of the Bernoulli law:

1. Venturimeter

Venturimeter is a device that is often used to measure the velocity of fluid flow. For example in calculating the speed of the flow of oil or flow that flows through the pipe.

2. Torriceli's Theorem

In Bernoulli's law equation, Daniel also uses this theorem to calculate the velocity of liquid that comes out of the base of a place to hold water.

3. Carburetor

Carbutator also has a purpose which is to be a device that can produce a mixture of fuel with air. Then the mixture can be put into the engine cylinder to be able to do combustion.

Example of the Problem and its Discussion

1. Pipes that are often used to channel water that sticks to a house wall as shown in the following figure have an area ratio in the cross section of a large pipe with a small pipe is 4: 1 . And the position of the large pipe is 5 m which is above the ground, and the small pipe is positioned 1 m above the ground. The speed of the flow of water to a large pipe is 36 km / h . And has a pressure of 9.1 x 105 Pa . If ρair = 1000 kg / m3.



  • Speed ​​of water in the small pipe
  • Difference in pressure in the two pipes
  • and the pressure in the small pipe


First, you must write down what is already known, and the following is what is already known:

  • V 1 = 36 km / h = 10 m / s
  • A 1 : A 2 = 4: 1
  • ] h 1 = 5m
  • h 2 = 1 m
  • P 1 = 9 , 1 x 105 Pa

What is being asked is:

a. The speed of water?

b. Difference between the two pipes?

c. Pressure on a small pipe?


a. What is the water velocity?

A 1 v 1 = A 2 v 2

] (4) (10) = (1) (v 2 )

V 2 = 40 m / s [19659002] b. What is the difference between the two pipes?

P1 + ½ ρv 12 + ρgh 1 = P2 1 1/2 ρv 22 + ρgh 2

P1 – P2 = ½ ρ (v 22 – v 12 ) + ρg (h 2 = h 1 )

P1 – P2 = ½ (1000) (402 – 102) + (1000) (10) (1 – 5 )

P1 – P2 = (500) (1500) – 40000 = 750000 – 40000

P1 – P2 = 710000 Pa = 7.1 x 105 Pa ]

c. What is the pressure on the small pipe?

P1 – P2 = 7.1 x 105

9.1 x 105 – P2 = 7.1 x 105

P2 = 2.0 x 105 Pa

Thus the article that explains the Bernoulli Law formula, its application and examples and discussion. Hopefully this article can be useful for you.


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