Homework Help

What is the formula for pressure?

user profile pic

ustaad | Student, Grade 9 | (Level 1) eNoter

Posted December 24, 2009 at 2:01 PM via web

dislike 2 like

What is the formula for pressure?

26 Answers | Add Yours

user profile pic

pohnpei397 | College Teacher | (Level 3) Distinguished Educator

Posted December 24, 2009 at 2:12 PM (Answer #1)

dislike 3 like

The formula for pressure is

P = F/A

In this equation, P stands for pressure while F stands for force and A stands for area.  Pressure is typically measured in a unit called the Pascal.

So what this means is that the amount of pressure that is exerted on an area is determined by the size of that area and by the amount of force that is pressing against it.

Therefore, if you have a given amount of force, you will have more pressure if it presses down on a small area than if it presses down on a large area.

user profile pic

neela | High School Teacher | (Level 3) Valedictorian

Posted December 25, 2009 at 1:38 AM (Answer #2)

dislike 3 like

Pressure is defined as the normal force per unit area of a surface. If F is the force acting normal to the surface area A,then the pressure P is given by :

P = F/A, Newtons/square meter or P = F/A Pascals.

According to the dimensional analysis of the pressure from this definition is: Force/Area = [M^1]*[L^1][T^(-2)]/[L^2]

= [M^1][L^(-1)][T^(-2)], where M  represents mass, L represents length and T represents time in fundamental  standard units.

 

 

 

user profile pic

giorgiana1976 | College Teacher | (Level 3) Valedictorian

Posted December 25, 2009 at 7:30 PM (Answer #3)

dislike 3 like

Pressure (symbol: p) is the force applied per unit area,  in the direction perpendicular to that surface.

P=F/A, where, F is the normal force, A is the area.

Pressure is a scalar, which in IS is measured in pascals.

1 Pa = 1 N/m2

The pressure is transmitted to surrounding areas or sections of the field of fluid, in the normal direction at any point in these areas or sections.

It is a fundamental parameter in thermodynamics and is a joint variable to volume.

Characteristic Cases

Static pressure

Static pressure, usually denoted SP, is the inner pressure of a fluid which is measured with a device that moves with the same speed as the fluid. For example, to the walls of a pipeline is carried the static pressure of fluid flowing through it.

Dynamic Pressure

Dynamic pressure is the additional pressure of a fluid that would hit an area and would be forced to consume completely it's kinetic energy. It is expressed by the relation:

p dynamic= rho*(v^2/2)

where rho is fluid density in kg/m^3, v is velocity in m / s.

Stagnation pressure

Stagnation pressure is the pressure that would exert a fluid in motion if it were forced to stop. If a fluid moves faster, its stagnation pressure increases. Static pressure and stagnation pressure are related to Mach number of fluid. See also Bernoulli's equation, which however is  valid only for incompressible fluids.Pressure of a fluid in motion can be measured with a Pitot tube, connected to a manometer.

 Hydrostatic pressure

Hydrostatic pressure is the pressure due to the weight of a fluid.

p=rho*g*h

where:

ρ (rho) is density of the fluid (eg water density is almost 1000 kg/m3);

g is the acceleration due to gravity (conventional, 9.80665 m/s2 to the sea surface);

h is the height of column of liquid (in meters).

Pressure of explosion or deflagration

Explosion or deflagration pressures are created by igniting explosive gas, aerosol, suspension in closed or open spaces. These pressures propagate as a wave of shock.

Negative pressures

While pressures are generally positive, in some cases negative pressures are meet:

-When discussing the relative pressures. For example, an absolute pressure of 80 kPa may be expressed as a relative pressure of -21 kPa (ie 21 kPa under atmospheric pressure of 101 kPa). The technique is called "a depression of 21 kPa.

- When attractive forces (eg Van der Waals forces) between particles of fluid, exceeds the forces of rejection. This scenario, however, is unstable because the particles are closer and closer until rejection forces would balance the forces of attraction.

- Negative pressures occurring during plant transpiration.

-Casimir effect can create small forces of attraction by interacting with vacuum energy. Sometimes this is called 'vacuum pressure' (not to be confused with depression).

- Depending on the reference system to surface orientation, a positive pressure on one side of a surface can be considered negative on the other side of the area.

- In cosmology( dark energy, expansion of the universe).

user profile pic

mkcapen1 | Middle School Teacher | (Level 3) Valedictorian

Posted December 24, 2009 at 4:20 PM (Answer #4)

dislike 2 like

Pressure is often listed as psi.  The formula to measure pressure is Pressure equals force in pounds over the area in square inch.  The written abbreviated formula is P= F/A.

By looking at the formula one can see that top obtain the pressure on an object, one must divide the the force by the area of an object.

All fluids, liquids, and gases omit pressure.  If a fluid is not moving it exerts even pressure.  Air pressure is measured by using a barometer.

user profile pic

user2630278 | eNotes Newbie

Posted October 13, 2014 at 11:39 AM (Answer #24)

dislike 1 like

Pressure is defined as the normal force per unit area of a surface.

If F is the force acting normal to the surface area A, then pressure P is given by:

FORMULA-P=F/A

user profile pic

astrosonuthird | Student | (Level 1) Valedictorian

Posted October 22, 2012 at 12:34 PM (Answer #5)

dislike 0 like

Hello!

The formulae for pressure is P= F/A

 

 

Bye!!

user profile pic

alejandrogalarce | Student, Undergraduate | (Level 1) Valedictorian

Posted October 12, 2013 at 5:46 PM (Answer #6)

dislike 0 like

Pressure is the amount of force acting perpedicularly per unit area. The symbol of pressure is p.

`p=(F/A)`

where;

p is the pressure

F is the normal force

A is the area of the surface on contact.

Pressure is a scalar quantity. It relates the vector surface element (a vector normal to the surface) with the normal force acting on it. The pressure is the scalar proportionality constantthat relates the two normal vectors.

Sources:

user profile pic

laurto | Student, Grade 10 | (Level 1) Valedictorian

Posted December 7, 2013 at 8:08 PM (Answer #7)

dislike 0 like

p=F/A 

p= pressure

F= normal force

A= area of surface on contact

user profile pic

laurto | Student, Grade 10 | (Level 1) Valedictorian

Posted December 10, 2013 at 8:05 PM (Answer #8)

dislike 0 like

p= F/A

p= pressure

F= force

A= area

user profile pic

Yojana_Thapa | Student, Grade 10 | (Level 1) Valedictorian

Posted January 25, 2014 at 10:35 PM (Answer #9)

dislike 0 like

Pressure= Force/Area

user profile pic

parama9000 | Student, Grade 11 | (Level 1) Valedictorian

Posted January 26, 2014 at 2:11 PM (Answer #10)

dislike 0 like

P=F/A

P PRESSURE

F FORCE

A AREA

user profile pic

Jyotsana | Student, Grade 10 | (Level 1) Valedictorian

Posted February 21, 2014 at 4:15 AM (Answer #11)

dislike 0 like

Pressure = Force/Area

user profile pic

nicole8923 | Student, Grade 10 | (Level 1) Salutatorian

Posted February 26, 2014 at 7:27 PM (Answer #12)

dislike 0 like

The formula for pressure is P= F/A

user profile pic

zumba96 | Student, Grade 11 | (Level 2) Valedictorian

Posted April 29, 2014 at 10:47 PM (Answer #13)

dislike 0 like

The formula of pressure is force divided by area of the surface area on contact. Pressure is the force per unit area applied in a route perpendicular to the surface of an object. It is a scalar quantity denoted by the symbol p.

user profile pic

Wiggin42 | Student, Grade 11 | (Level 2) Valedictorian

Posted May 24, 2014 at 8:01 PM (Answer #14)

dislike 0 like

The formula for pressure is: 

P = F/A 

where P is pressure, F is force and A is area. 

The SI  unit for pressure is the Pascal  ( Pa ) which stands for:  `N/m^2`

`<span style="font-size: 14px;">The standard system uses psi or pounds per square inch. </span>`

`<span style="font-size: 14px;">Torr and mm Hg (read: millimeter Mercury) are also pressure units. </span>`

`<span style="font-size: 14px;">Atm is also a unit of pressure and as you can guess is </span>`equivalent to the pressure of Earth's atmosphere. 

To convert between the major units: 

1 Atm = 101 kPa = 760 Torr = 760 mm Hg = 14.5 psi

user profile pic

atyourservice | Student, Grade 10 | (Level 3) Valedictorian

Posted May 25, 2014 at 11:59 PM (Answer #15)

dislike 0 like

the formula for pressure is pressure = force/area

user profile pic

acompanioninthetardis | Student, Undergraduate | (Level 1) Valedictorian

Posted May 28, 2014 at 1:30 AM (Answer #16)

dislike 0 like

pressure=force/area

p=f/a

user profile pic

rimmery | Student, Undergraduate | (Level 1) Honors

Posted May 31, 2014 at 1:38 AM (Answer #17)

dislike 0 like

P=F/A

where P is for pressure, usually measured in Pascals

F is force, how much force you're applying 

A is for surface area upon which the pressure is being applied on

The formula states that the pressure exerted on an area is evenly distributed by the amount of force applied onto that area.

user profile pic

arrellbelle | Student, College Sophomore | (Level 1) Valedictorian

Posted June 6, 2014 at 4:49 PM (Answer #18)

dislike 0 like

The formula for pressure is P=F/A

P = Pressure

F = Force being applied

A = (Surface) area on which the pressure is being applied to.

user profile pic

jess1999 | TA , Grade 9 | (Level 1) Valedictorian

Posted June 17, 2014 at 5:48 AM (Answer #19)

dislike 0 like

The formula for pressure is P = F / A

F  = Force that is applied

A = Total area of the subject or also known as surface area

P = pressure

Ex:Calculate the pressure produced by a force of 900 N acting on an area of 3.0 m2

P=900/3

=300 Pa

user profile pic

ik9744 | TA , Grade 9 | (Level 1) Valedictorian

Posted June 26, 2014 at 6:34 AM (Answer #20)

dislike 0 like

P= F/A

P Pressure

Force

Area

user profile pic

acompanioninthetardis | Student, Undergraduate | (Level 1) Valedictorian

Posted June 30, 2014 at 7:18 PM (Answer #21)

dislike 0 like

pressure= force/area

user profile pic

rachellopez | TA , Grade 12 | (Level 1) Valedictorian

Posted August 9, 2014 at 8:02 PM (Answer #22)

dislike 0 like

"Pressure is defined as force per unit area." The formula for pressure is `P = (F)/(A)`, which stands for `Pressure = (Force)/(Area)`. You could use this formula for many different things, but one example would be the difference in force between an object placed at different angles. There is a photo on the website I linked below.

Sources:

user profile pic

hardikjain | eNotes Newbie

Posted September 5, 2014 at 2:38 PM (Answer #23)

dislike 0 like

Pressure =  Force / Area 

SI system :

  1. Unit of force - Newton (N)
  2. Unit of area - m^2
  3. Unit of pressure - Pa
  4. 1 Pa = 1 N/m^2

Cgs system

  1. Unit of force - Dyne
  2. Unit of area - cm^2
  3. Unit of pressure - Barye 
  4. 1 Barye = 1 Dyne /cm^2

Basically pressure is directly proportional to force and inversely proportional to area.

I other words more force and less area means more pressure.

user profile pic

strwbrry16 | TA , Grade 5 | (Level 1) Valedictorian

Posted October 20, 2014 at 3:01 PM (Answer #26)

dislike 0 like

This link can guide you. It has even examples in it. Hope it helps. :)

Sources:

user profile pic

ibrahimrehan | TA , Grade 9 | (Level 2) Honors

Posted October 22, 2014 at 7:37 PM (Answer #27)

dislike 0 like

Pressure in solid is equal force divided by its area where s in liquids  the pressure is equal to density of the liquid multiplied by its depth multiplied by the gravitational field strength 

Hence Pressure =Force (F) / area (A) in solids 

and P = density (d) x depth (h) x gravitational field strength (g=10) .

Join to answer this question

Join a community of thousands of dedicated teachers and students.

Join eNotes