Unit 2 mechanics
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UNIT 2 - MECHANICS. CHAPTER 8 - FLUID MECHANICS. Chapter 8A – Properties of Fluids. Objectives: Identify what is studied in fluid mechanics Define pressure Show how different physical properties affect pressure Calculate pressure when given applied force and area

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Unit 2 mechanics



Chapter 8a properties of fluids
Chapter 8A – Properties of Fluids

  • Objectives:

    • Identify what is studied in fluid mechanics

    • Define pressure

    • Show how different physical properties affect pressure

    • Calculate pressure when given applied force and area

    • Recognize units of pressure

    • Discuss the factors affecting fluid pressure in natural and manmade settings

    • Describe how instruments measure pressure

    • State Archimedes’ principle in your own words

    • Calculate specific gravity

  • Assignment: Section Review, page 181

Fluid mechanics
Fluid Mechanics

  • The study of how fluids flow and how forces and energy are transmitted through fluids

  • Divided into two parts

    • Hydrostatics

      • The scientific study of fluids, especially non-compressible liquids, in equilibrium with their surroundings and hence at rest

    • Hydrodynamics

      • The scientific study of the motion of fluids, especially non-compressible liquids, under the influence of internal and external forces

  • Fluids

    • Matter that assumes the shape of their containers

    • Both liquids and gases are fluids


  • The force exerted perpendicularly on a unit of area

  • Units are Pascals (N/m2)

  • Formula

  • P=F/A

  • P=pressure F=force A=total surface area

  • Larger area = lower pressure

Fluid pressure
Fluid Pressure

  • A property of all fluids in which pressure is exerted equally in all directions at any point in the fluid

  • Exists because liquid and gas particles are not held rigidly in place

  • Kinetic theory??

Factors affecting fluid pressure
Factors Affecting Fluid Pressure

  • Let’s Read page 176

  • Gravity and fluid properties

    • Fluid’s have weight

    • Pressure is not affected by the volume or shape of the container

    • Fluid density

  • Hydrostatic pressure

    • Water pressure due only to depth in a body of water

Pressure instruments
Pressure Instruments

  • Evangelista Torricelli

    • Served as Galileo’s secretary

    • Created the first true vacuum and invented the mercury barometer

      • An instrument that measures atmospheric pressure and consists of a column of mercury in a sealed glass tube containing a vacuum

  • Aneroid barometer

    • An instrument for measuring atmospheric pressure that consists of a sealed flexible can that expands and contracts with changes in air pressure

  • Gauges

    • A mechanical device connected to a fluid system designed to indicate gas or liquid pressure

    • Bourdon Tube


  • Let’s Read page 179, section 8.4

  • Archimedes’ principle

    • States that the buoyant force exerted by a fluid on an immersed object is equal to the weight of the fluid the object displaces

  • Buoyant force

    • A lifting force exerted by a fluid on an immersed object

  • Positively buoyant – objects that float

  • Negatively buoyant – objects that sink

  • Neutrally buoyant – do not rise or sink

Specific gravity
Specific Gravity

  • The ratio of a substance’s density to water’s density

  • A unitless quantity numerically equal to the density of the substance

  • Also called relative density

  • Let’s Read page 181

Chapter 8b hydraulics fluid flow
Chapter 8B – Hydraulics & Fluid Flow

  • Objectives:

    • State Pascal’s principle and discuss the conditions under which it applies

    • Describe a simple hydraulic machine and how it relates to other simple machines

    • Discuss the causes of fluid flow and explain how they apply in familiar examples

    • Summarize Bernoulli’s principle and identify the three quantities whose sum must be conserved in a closed fluid system

    • List the characteristics of two principal kinds of fluid systems that obey Bernoulli’s principle

    • Describe the Coanda effect and explain how it is responsible for exerting forces in fluids

  • Assignment: Section Review, page 188

Pascal s principle
Pascal’s Principle

  • Let’s Read page 182, section 8.6 & 8.7

  • States that changes of pressure on the surface of a confined fluid are exerted equally throughout the fluid and at all points on the fluids’ container

  • Hydraulic machine

    • A liquid filled machine that uses Pascal’s principle to convert a small force exerted on a small diameter piston to a large force exerted by a large diameter piston to do work

  • Hydraulics

    • The area of physics that deals with the transfer of forces and work done by confined fluids according to Pascal’s principle

Flowing fluids
Flowing Fluids

  • How does water get from the pipes to your sink?

  • How does a vacuum work?

  • What about when you breathe?

  • Let’s Read page 183, section 8.8

Bernoulli s principle
Bernoulli’s Principle

  • States that total energy (represented by kinetic energy, potential energy, and pressure) for a confined ideal fluid flowing through a pipe is conserved at all locations within the pipe

  • Let’s Read page 185, section 8.9

  • Venturi

    • A specially designed constriction in a pipe, used to measure fluid flow rate by comparing the differences in fluid pressure before and within the constriction that occur according to Bernoulli’s principle

Coanda effect
Coanda Effect

  • The tendency of a fluid flowing past a curved surface to follow the surface

  • Let’s Read page 186, section 8.10

  • Lift

    • The supporting force on an air foil or hydrofoil created as it moves through a fluid

  • Air foil

    • A streamlined shape designed to produce life as it moves through the air or as air moves past it

  • Facet, page 187

Chapter 8c gas laws
Chapter 8C – Gas Laws

  • Objectives:

    • Summarize the history of the discovery of the gas laws

    • State Boyle’s law

    • Show how Boyle’s law is predicted by the particle theory of matter

    • Perform calculations using Boyle’s law

    • State Charles’s law

    • Show how Charles’s law is predicted by the particle theory

    • Perform calculations using Charles’s law

  • Assignment: Section Review, page 194

Lots of scientists in this chapter
Lots of Scientists in this Chapter!!

  • So Far…

    • Blaise Pascal

    • Evangelista Torricelli

    • Eugene Bourdon

    • Archimedes

    • Daniel Bernoulli

    • Henri Marie Coanda

  • Coming Up…

    • Guillaume Amontons

    • John Dalton

    • Joseph Gay-Lussac

    • Amedeo Avogadro

    • Robert Boyle

    • Jacques Charles

      Extra Credit????

Boyle s law
Boyle’s Law

  • States that the volume of a fixed quantity of a confined gas is inversely proportional to its pressure when its temperature is held constant

  • Formula:

    • P1V1=P2V2

    • P=pressure V=volume

  • Example Problem 8-1 & 8-2

  • How is this useful??

    • Compressed air?

Charles s law
Charles’s Law

  • States that the volume of a fixed quantity of a confined gas is directly proportional to its absolute temperature when its pressure is held constant

  • Formula:

    • V1/T1 = V2/T2

    • V=volume T=temperature in Kelvin!

  • How do we get Kelvin from Celsius??

  • Example Problem 8-3

  • Facet, page 195


  • Vocabulary Quiz

    • Includes all vocabulary throughout the entire chapter, PowerPoints, and board; not just the box at the end.

  • Complete Chapter Review in Class

  • Study for Chapter 8 Test