4.4.13
Pressure
Pressure
Pressure
Pressure is the force per unit of area.


Force on container
Force on container
- In fluids (liquids or gases), the particles collide with the walls of their container.
- The particle exerts a force on the container and the container exerts a force on the particle.


Force at right angles
Force at right angles
- The force exerted on the surface in contact with the fluid particle will be at the normal to the surface (at right angles).


Equation
Equation
- Pressure is defined as the force divided by the area perpendicular to the force over which the force is applied, or:


Units
Units
- The SI unit for pressure is the pascal, where:
- 1 Pa = 1 N/m2.
Variation of Pressure with Depth
Variation of Pressure with Depth
If your ears have ever popped on a plane flight or ached during a deep dive in a swimming pool, you have experienced the effect of depth on the pressure of a fluid.


Pressure due to the weight of a fluid
Pressure due to the weight of a fluid
- The pressure exerted on the bottom of a container by the weight of the fluid is:
- We can find the mass of the fluid from its volume and density:


Pressure due to the weight of a fluid
Pressure due to the weight of a fluid
- The volume of the fluid is equal to , where is the cross-sectional area and is the depth.
- Substituting the equations for mass and volume into the pressure equation gives:
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Atmospheric pressure
Atmospheric pressure
- Atmospheric pressure is another example of pressure due to the weight of a fluid that is due to the weight of air above a given height.
- The atmospheric pressure at the Earth's surface varies a little due to the large-scale flow of the atmosphere induced by the Earth's rotation.
- However, the average pressure at sea level is given by the standard atmospheric pressure .
- = 1 atmosphere = 1.01 × 105 N/m2 = 101 kPa
1Physical Quantities & Units
2Measurement Techniques
3Kinematics
4Dynamics
4.1Momentum & Newton's Laws of Motion
4.2Non-Uniform Motion
4.3Linear Momentum & Conservation
4.4Force, Density & Pressure
4.4.1Fields
4.4.2Force in Uniform Fields
4.4.3Friction
4.4.4Buoyancy
4.4.5Terminal Speed
4.4.6End of Topic Test - Acceleration Due to Gravity
4.4.7Centre of Mass
4.4.8Forces & Equilibrium
4.4.9End of Topic Test - Scalars & Vectors
4.4.10Moments
4.4.11End of Topic Test - Moments & Centre of Mass
4.4.12Density
4.4.13Pressure
4.5Work, Energy & Power
5Gravitational Fields
5.1Gravitational Fields (A2 only)
6Deformation of Solids
7Thermal Physics
7.1Thermal Physics
7.1.1Temperature
7.1.2Measuring Temperature
7.1.3Ideal Gas Law
7.1.4Ideal Gases
7.1.5Boyle's Law & Charles' Law
7.1.6Molecular Kinetic Theory Model
7.1.7Molecular Kinetic Theory Model 2
7.1.8Thermal Energy Transfer
7.1.9Thermal Energy Transfer Experiments
7.1.10End of Topic Test - Thermal Energy & Ideal Gases
7.1.11First Law of Thermodynamics
8Oscillations
8.1Simple Harmonic Motion
8.2Waves
8.2.1Progressive Waves
8.2.2Intensity of Waves
8.2.3Wave Speed & Phase Difference
8.2.4Longitudinal & Transverse Waves
8.2.5End of Topic Test - Progressive Waves
8.2.6Electromagnetic Waves
8.2.7Doppler Effect
8.2.8Sound Waves
8.2.9Measuring Sound Waves
8.2.10End of Topic Test - Waves
8.2.11Ultrasound Imaging
8.2.12Ultrasound Imaging 2
9Communication
9.1Communication Channels
9.2Digital Communication
10Electric Fields
10.1Electric Fields
11Current Electricity
11.1Current Electricity
11.1.1Basics of Electricity
11.1.2Mean Drift Velocity
11.1.3Current-Voltage Characteristics
11.1.4End of Topic Test - Basics of Electricity
11.1.5Resistivity
11.1.6End of Topic Test - Resistivity & Superconductors
11.1.7Power and Conservation
11.1.8Microphones
11.1.9Components
11.1.10Relays
11.1.11Strain Gauges
12Magnetic Fields
12.1Magnetic Fields
13Modern Physics
13.1Quantum Physics
13.1.1The Photoelectric Effect
13.1.2The Photoelectric Effect Explanation
13.1.3End of Topic Test - The Photoelectric Effect
13.1.4Collisions of Electrons with Atoms
13.1.5Energy Levels & Photon Emission
13.1.6Wave-Particle Duality
13.1.7End of Topic Test - Absorption & Emission
13.1.8Band Theory
13.1.9Diagnostic X-Rays
13.1.10X-Ray Image Processing
13.1.11Absorption of X-Rays
13.1.12CT Scanners
13.2Nuclear Physics
13.2.1Rutherford Scattering
13.2.2Atomic Model
13.2.3Isotopes
13.2.4Stable & Unstable Nuclei
13.2.5A-A* (AO3/4) - Stable & Unstable Nuclei
13.2.6Alpha & Beta Radiation
13.2.7Gamma Radiation
13.2.8Particles, Antiparticles & Photons
13.2.9Quarks & Antiquarks
13.2.10Particle Interactions
13.2.11Radioactive Decay
13.2.12Half Life
13.2.13End of Topic Test - Radioactivity
13.2.14Nuclear Instability
13.2.15Mass & Energy
13.2.16Binding Energy
13.2.17A-A* (AO3/4) - Nuclear Fusion
Jump to other topics
1Physical Quantities & Units
2Measurement Techniques
3Kinematics
4Dynamics
4.1Momentum & Newton's Laws of Motion
4.2Non-Uniform Motion
4.3Linear Momentum & Conservation
4.4Force, Density & Pressure
4.4.1Fields
4.4.2Force in Uniform Fields
4.4.3Friction
4.4.4Buoyancy
4.4.5Terminal Speed
4.4.6End of Topic Test - Acceleration Due to Gravity
4.4.7Centre of Mass
4.4.8Forces & Equilibrium
4.4.9End of Topic Test - Scalars & Vectors
4.4.10Moments
4.4.11End of Topic Test - Moments & Centre of Mass
4.4.12Density
4.4.13Pressure
4.5Work, Energy & Power
5Gravitational Fields
5.1Gravitational Fields (A2 only)
6Deformation of Solids
7Thermal Physics
7.1Thermal Physics
7.1.1Temperature
7.1.2Measuring Temperature
7.1.3Ideal Gas Law
7.1.4Ideal Gases
7.1.5Boyle's Law & Charles' Law
7.1.6Molecular Kinetic Theory Model
7.1.7Molecular Kinetic Theory Model 2
7.1.8Thermal Energy Transfer
7.1.9Thermal Energy Transfer Experiments
7.1.10End of Topic Test - Thermal Energy & Ideal Gases
7.1.11First Law of Thermodynamics
8Oscillations
8.1Simple Harmonic Motion
8.2Waves
8.2.1Progressive Waves
8.2.2Intensity of Waves
8.2.3Wave Speed & Phase Difference
8.2.4Longitudinal & Transverse Waves
8.2.5End of Topic Test - Progressive Waves
8.2.6Electromagnetic Waves
8.2.7Doppler Effect
8.2.8Sound Waves
8.2.9Measuring Sound Waves
8.2.10End of Topic Test - Waves
8.2.11Ultrasound Imaging
8.2.12Ultrasound Imaging 2
9Communication
9.1Communication Channels
9.2Digital Communication
10Electric Fields
10.1Electric Fields
11Current Electricity
11.1Current Electricity
11.1.1Basics of Electricity
11.1.2Mean Drift Velocity
11.1.3Current-Voltage Characteristics
11.1.4End of Topic Test - Basics of Electricity
11.1.5Resistivity
11.1.6End of Topic Test - Resistivity & Superconductors
11.1.7Power and Conservation
11.1.8Microphones
11.1.9Components
11.1.10Relays
11.1.11Strain Gauges
12Magnetic Fields
12.1Magnetic Fields
13Modern Physics
13.1Quantum Physics
13.1.1The Photoelectric Effect
13.1.2The Photoelectric Effect Explanation
13.1.3End of Topic Test - The Photoelectric Effect
13.1.4Collisions of Electrons with Atoms
13.1.5Energy Levels & Photon Emission
13.1.6Wave-Particle Duality
13.1.7End of Topic Test - Absorption & Emission
13.1.8Band Theory
13.1.9Diagnostic X-Rays
13.1.10X-Ray Image Processing
13.1.11Absorption of X-Rays
13.1.12CT Scanners
13.2Nuclear Physics
13.2.1Rutherford Scattering
13.2.2Atomic Model
13.2.3Isotopes
13.2.4Stable & Unstable Nuclei
13.2.5A-A* (AO3/4) - Stable & Unstable Nuclei
13.2.6Alpha & Beta Radiation
13.2.7Gamma Radiation
13.2.8Particles, Antiparticles & Photons
13.2.9Quarks & Antiquarks
13.2.10Particle Interactions
13.2.11Radioactive Decay
13.2.12Half Life
13.2.13End of Topic Test - Radioactivity
13.2.14Nuclear Instability
13.2.15Mass & Energy
13.2.16Binding Energy
13.2.17A-A* (AO3/4) - Nuclear Fusion
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