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Chapter 3: Chapter 3: Forces & PressureForces & Pressure

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PhysicsPhysicsNext >

The study of The study of mattermatter

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Objectives: Objectives: ((what you will learnwhat you will learn)) 1) understanding Pressure

2) understanding the Principles

Physics: Chapter Physics: Chapter 33

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PressurePressure

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Pressure = force per unit area

Pressure, P

= Force, FArea, A , N m-2 or Pa

(Pascal)If a fluid (liquid or gas) has a density ρ, its pressure P, at a point due to the fluid of height h, is given byP = ρgh where g = gravitational field

strength

For a given point in the fluid, its pressure acts equally in all directions.

It does not depend on the shape of containers.

Therefore, for a given liquid, its pressure:- increases with depth- increases with density

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AtmosphereAtmosphereAtmosphere is the layer of thick air which surrounds the Earth.

The pressure exerted on the Earth’s surface by the atmosphere is the atmospheric pressure, which can be measured using Fortin barometer or Aneroid barometer.

1 atmosphere

= 760 cm Hg

= 10.3 m water

= 101,300 Pa

1 millibar = 100 Pa

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The PrinciplesThe PrinciplesPascal’s Principle:

The pressure applied to an enclosed liquid is transmitted equally to all parts of the liquid.

Archimedes’ Principle:

When an object is immersed in a fluid the buoyant force on the object is equal in size to the weight of fluid displaced by the object.

Bernoulli’s Principle:

When the velocity of a fluid increases, the pressure of the fluid decreases.

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SummarySummary

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What you have learned:What you have learned:

1.1. Understanding Understanding PressurePressure

2.2. Understanding theUnderstanding the Principles Principles

Thank YouThank You