<< Chapter < Page Chapter >> Page >
  • Define pressure.
  • State Pascal’s principle.
  • Understand applications of Pascal’s principle.
  • Derive relationships between forces in a hydraulic system.

Pressure is defined as force per unit area. Can pressure be increased in a fluid by pushing directly on the fluid? Yes, but it is much easier if the fluid is enclosed. The heart, for example, increases blood pressure by pushing directly on the blood in an enclosed system (valves closed in a chamber). If you try to push on a fluid in an open system, such as a river, the fluid flows away. An enclosed fluid cannot flow away, and so pressure is more easily increased by an applied force.

What happens to a pressure in an enclosed fluid? Since atoms in a fluid are free to move about, they transmit the pressure to all parts of the fluid and to the walls of the container. Remarkably, the pressure is transmitted undiminished . This phenomenon is called Pascal’s principle , because it was first clearly stated by the French philosopher and scientist Blaise Pascal (1623–1662): A change in pressure applied to an enclosed fluid is transmitted undiminished to all portions of the fluid and to the walls of its container.

Pascal’s principle

A change in pressure applied to an enclosed fluid is transmitted undiminished to all portions of the fluid and to the walls of its container.

Pascal’s principle, an experimentally verified fact, is what makes pressure so important in fluids. Since a change in pressure is transmitted undiminished in an enclosed fluid, we often know more about pressure than other physical quantities in fluids. Moreover, Pascal’s principle implies that the total pressure in a fluid is the sum of the pressures from different sources . We shall find this fact—that pressures add—very useful.

Blaise Pascal had an interesting life in that he was home-schooled by his father who removed all of the mathematics textbooks from his house and forbade him to study mathematics until the age of 15. This, of course, raised the boy’s curiosity, and by the age of 12, he started to teach himself geometry. Despite this early deprivation, Pascal went on to make major contributions in the mathematical fields of probability theory, number theory, and geometry. He is also well known for being the inventor of the first mechanical digital calculator, in addition to his contributions in the field of fluid statics.

Application of pascal’s principle

One of the most important technological applications of Pascal’s principle is found in a hydraulic system , which is an enclosed fluid system used to exert forces. The most common hydraulic systems are those that operate car brakes. Let us first consider the simple hydraulic system shown in [link] .

A small force can be converted into a larger force when pressure is transmitted through liquids in different containers with pistons that are connected.
A typical hydraulic system with two fluid-filled cylinders, capped with pistons and connected by a tube called a hydraulic line. A downward force F 1 size 12{F rSub { size 8{1} } } {} on the left piston creates a pressure that is transmitted undiminished to all parts of the enclosed fluid. This results in an upward force F 2 size 12{F rSub { size 8{2} } } {} on the right piston that is larger than F 1 size 12{F rSub { size 8{1} } } {} because the right piston has a larger area.

Questions & Answers

Calculate the final velocity attained, when a ball is given a velocity of 2.5m/s, acceleration of 0.67m/s² and reaches its point in 10s. Good luck!!!
Eklu Reply
2.68m/s
Doc
express your height in Cm
Emmanuel Reply
hii
Bala
my project is Sol gel process how to prepare this process pls tell me
Bala
the dimension of work and energy is ML2T2 find the unit of work and energy hence drive for work?
Emmanuel Reply
KgM2S2
Acquah
Two bodies P and Quarter each of mass 1000g. Moved in the same direction with speed of 10m/s and 20m/s respectively. Calculate the impulse of P and Q obeying newton's 3rd law of motion
Shimolla Reply
kk
Doc
definition for wave?
Doc Reply
A disturbance that travel from one medium to another and without causing permanent change to its displacement
Fagbenro
In physics, a wave is a disturbance that transfers energy through matter or space, with little or no associated mass transport (Mass transfer). ... There are two main types ofwaves: mechanical and electromagnetic. Mechanicalwaves propagate through a physical matter, whose substance is being deformed
Devansh
K
Manyo
thanks jare
Doc
Thanks
AMADI
Note: LINEAR MOMENTUM Linear momentum is defined as the product of a system’s mass multiplied by its velocity: size 12{p=mv} {}
AMADI
what is physic
zalmia Reply
please gave me answar
zalmia
Study of matter and energy
Fagbenro
physics is the science of matter and energy and their interactions
Acquah
physics is the technology behind air and matter
Doc
Okay
William
hi sir
Bala
how easy to understanding physics sir
Bala
Easy to learn
William
31. Calculate the initial (from rest) acceleration of a proton in a 5.00×106 N/C electric field (such as created by a research Van de Graaff). Explicitly show how you follow the steps in the Problem-Solving Strategy for electrostatics.
Catina Reply
A tennis ball is projected at an angle and attains a range of 78. if the velocity is 30metres per second, calculate the angle
Shimolla
what friction
Wisdom Reply
question on friction
Wisdom
the rubbing of one object or surface against another.
author
momentum is the product of mass and it's velocity.
Algayawi
what are bioelements?
Edina
Friction is a force that exist between two objects in contact. e.g. friction between road and car tires.
Eklu
With regards to a shielded cable, is there an induced current on the shield when the center conductor is carrying an AC Current? What is the formula?
John Reply
what is phenomena
remilekun Reply
no idea
Awoke
its phenomenon, an observable fact.
author
Mujy achy marks hasil krny k leay kesy tayari krni ho ge?plz help me I'M sooo woried
Imran Reply
konsi university m ho and konsa course h
Mohit
what is force
Chukwuemeka Reply
Force is the cause and momentum is its effect.
Salman
A force is a pull or a push on an object, causing an object to move or a moving object to stop.
Eklu
Find the velocity that make one full oscillation in 10 seconds and also makes 1.7meters in the same time
Prince Reply
yes
Rafael
OK
Oluwaseun
17m/s
Eklu
17m/s
Gabriel
0.17
Devansh
17m/s
Harrison
how did you solve it
Acquah
t=10s a=1.7m v=? u=0 but v=u+at but u=0 v=at 1.7×10=17 v=17m/s that's how I solved it.
Eklu
kk
Acquah
How is a=1.7m?
El
a is an acceleration
El
eklu..... I respect u....
Doc
its relating to time and oscillation made.
Eklu
You mean A as an amplitude?
El
ok
Emmanuel
what is voltmeter
Jeremiah Reply
A voltmeter is a device use in measuring electric potential in a volt.
Ahmad
Find out the equation of a simple harmonic progressive wave that have 0.2m with a frequency of 550hertz.If the wave moves along a positive x axis with the speed of 330m/s
Joseph Reply
Practice Key Terms 1

Get the best College physics course in your pocket!





Source:  OpenStax, College physics. OpenStax CNX. Jul 27, 2015 Download for free at http://legacy.cnx.org/content/col11406/1.9
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'College physics' conversation and receive update notifications?

Ask