Pascal’s Law: Definition, Formulas, Problems and Discussion, and Benefits

Pascal’s Law – When You is engrossed in driving, be it using a bicycle or motorbike, have you ever experienced a sudden flat tire? If that happened, surely You would immediately push his vehicle to the tire repair shop, right ? However, what if the leak is a car tire? Will You also push the car to the nearest tire patch? Of course not , because it’s really hard, especially when you’re alone. So, to anticipate this, usually a replacement tire and a hydraulic jack will be provided in the car. Yep, a hydraulic jack is a special tool that can be used to lift certain car parts, one of which is the tire.

Did You know that the process of lifting a car tire using a hydraulic jack was not arbitrary, but had to be based on the principles of Physics, namely Pascal’s Law? Yep, the process of jacking up car tires turns out to require calculations, just like Physics in general. Then, what is Pascal ‘s Law? How does Pascal’s Law sound? How is the application of Pascal’s law to everyday human life? So, so that You can understand these things, let’s look at the following review!

How Does Pascal’s Law Sound?

Basically, Pascal’s law is indeed part of various physical laws which turn out to provide benefits for everyday human life. Pascal’s law reads ” The pressure exerted on a liquid in a closed space is transmitted equally in all directions”. Pascal’s law was created by a French physicist named Blaise Pascal.

A simple example is you have a perforated plastic bag filled with water and then squeezed out, what would happen? Now, when you squeeze the plastic bag filled with water, there will be pressure on the water in the bag, causing two things:

  • Water will gush out of the bag openings. That means, the pressure you exerted earlier, is transmitted through the water in the bag.
  • Water gushes from each hole with equal force. That means pressure in the water, acting in all directions.

Based on this simple example, it can be said that Pascal’s Law is a law of fluid physics which explains that from the presence of pressure exerted on a static fluid in a confined space, it will later be forwarded in all directions, which of course is with the same strong pressure.

Just a little trivia , You , Pascal’s Law was coined by a French physicist named Blaise Pascal, who was born in Clermont on July 19, 1623. Actually, Blaise Pascal was not only a physicist, but also a philosopher and theologian. However, he really likes things in the fields of mathematics and physics, especially in terms of projective geometry, which later led him to become an expert in the field of fluid mechanics physics, especially those related to pressure and force.

Moreover, when he was 18 years old, Pascal was able to create the world’s first digital calculator! Pascal spent his time playing and experimenting, even during his current cancer treatment. Pascal’s law was discovered when he was experimenting with water. At that time, Pascal was conducting experiments on water and stated that water would come out faster and farther through the hole in a container with an open top surface, when compared to a container with a closed top surface. Well, that’s what causes the water pressure to be greater than the open container.

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Pascal’s Law Formulas

Basically, Pascal’s Law is a working principle that has a relationship between the pressure caused by a liquid in a closed space. Pascal’s law illustrates that any increase in pressure on the surface of the fluid must be forwarded in all directions of the fluid. Pascal’s law is only applied to fluids, especially liquid fluids. It should be noted that fluids are substances that easily flow, such as liquids and gases.

Just a little information , yes , fluids are all substances that can flow. This flowing substance, of course, has the ability to form according to the container that holds it. For example, the liquid is accommodated in a bucket container, it will form like the bucket. It should also be noted that the atoms and molecules of the fluid move freely.

In this case, fluids have several types, namely static fluids and dynamic fluids.

Well, here is an explanation of Pascal’s Law if it is applied in a closed U-shaped vessel.


P1 = Pressure on first suction (N/m²)

P2 = Pressure at second suction (N/m²)

F1 = Force on the first suction (N)

F2 = Force on the second suction (N)

A1 = Area on first suction (m²)

A2 = Area on the second suction (m²)

Based on Pascal’s Law, pressure (P) will later be forwarded in all directions equally to suction 2. So, suction 2 with a cross-sectional area A2 will receive pressure (P1). If, there is a force generated by pressure (P1) on cross section A2, then it becomes a force (F), so the following equation will be obtained:

F 1 = force on A 1 (N)

F 2 = force on A 2 (N)

A 1 = cross sectional area 1 (m² )

A 2 = cross-sectional area 2 (m² )

This is because A2 > A1, then F2 > F1, causing the force acting on the cross section of A2 to be greater.

Questions and Discussion of Pascal’s Law

In order for You to understand more about Pascal’s Law, try to look at the questions and discussion below!

1. There is a hydraulic lifter which has two suction cups with respective cross-sectional areas A 1 = 100 cm2 , and A 2 = 2000 cm2 . What is the minimum force , F , that must be exerted on cross section A 1 so that a car weighing 15,000 N can be lifted?


Noted that:

A1 = 100 cm2

A 2 = 2000 cm2

w = F 2 , = 15,000 N

If applied using the working principle of Pascal’s Law, it will become:

So, the minimum force (F) needed to lift the car is 750 N.

2. There is a hydraulic jack with a large cross-sectional radius of 2 cm, while the small cross-sectional radius is 25 cm. What force (F) is exerted by the small section to lift a 2 ton truck?


Noted that:

r1 = 2 cm = 0.02 m
r2 = 25 cm = 0.25 m
A1 = (3.14)(0.02)2 = 0.001256 m2
A2 = (3.14)(0.25)2 = 0.19625 m2
F2 = w = mg = (2000). 10 = 20,000 N

Asked : F1 ?

F1/A1 = F2/A2
F1/0.001256 = 20,000/0.19625
0.19625 x F1 = (20,000) x 0.001256

F1 = 25.12/0.19625 = 28 N

So, the force needed to lift a truck weighing 2 tons is 28 N.

Benefits of Pascal’s Law in Human Life

The existence of Pascal’s Law is not merely just an ordinary calculation, you know, it turns out that its working principle can also be applied and proven to be useful for everyday human life. Remember that Blaise Pascal gained an understanding of Pascal’s Law after he conducted an experiment using a sprayer, which then stated that the pressure exerted on a liquid in a closed space can later be transmitted in all directions with the same force. Then, what are the benefits of Pascal’s law in human everyday technology? Let’s look at the following reviews!

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1. Hydraulic Jack

Generally, this hydraulic jack is used to lift heavy loads with a small force. The hydraulic jack will have two tubes of different sizes, one large diameter and the other small diameter, then the two tubes are filled with water. Then, each of them is also equipped with suction. The pressure exerted on the small suction cup will then be forwarded to the large suction cup. Meanwhile, a large suction will produce a much greater upward lift. That is why the existence of this hydraulic jack can be used to lift heavy loads, especially to hold the car when changing tires.

2. Car Lifting Tool

Of course, You is no stranger to this car lift, because usually it can be easily found in car repair shops, showrooms, and car wash places. The working principle of this car lifter uses air that has high pressure, then is inserted through one of the two taps in the tool. The air is then compressed in a room to produce a large pressure. The large pressure will then be forwarded by oil to a larger suction cup. Through that pressure, it will generate a very large lift force to be able to lift even a car.

After that, lowering the car can be done by removing the compressed air through the other faucet, namely the air outlet faucet.

3. Hydraulic Brake

These hydraulic brakes are usually on vehicles, one of which is a bicycle. The main parts of hydraulic brakes will usually contain the brake pedal, master cylinder, clamp shoes, and brake fluid. When the brake pedal is pressed with our foot, the pressure will be transmitted by the brake fluid to the clamp shoe through the brake cylinder. In this case, the brake cylinder would have 4 brake cylinders, with two at the front and two at the rear.

Meanwhile, the flip-flops will produce a very large frictional force, so that they can stop the rotation of the wheels of the vehicle. This is also due to the suction area of ​​the brake cylinder which is much larger than the suction area of ​​the master cylinder.

Understanding What is a Hydraulic System

The hydraulic system will not be separated from Pascal’s Law, because it is an application of the use of these physical laws. Basically, the hydraulic system becomes a system that uses liquid fluid power to do simple jobs. Yep, the hydraulic system is a power transfer system that uses liquid or fluid as an intermediary. In fact, this hydraulic system has many advantages compared to mechanical systems. Some of the advantages are in the form of:

  • Can channel great force.
  • Not difficult for overload prevention.
  • Operating style control becomes easier fast.
  • Speed ​​switching becomes easier.
  • The vibrations generated are relatively small.
  • Longer endurance.

Unfortunately, even though this hydraulic system has many advantages, there are still disadvantages, namely:

  • Sensitive to leaks.
  • Sensitive to changes in temperature.
  • Sometimes the work speed changes.
  • Channel system work is not simple.

So, that’s a review of what Pascal’s law is and its application in tools that make it easier for humans to live their daily lives. Has You ever used a hydraulic jack to change a car tire?