UNIT 2 - MECHANICS - PowerPoint PPT Presentation

1 / 19

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

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

UNIT 2 - MECHANICS

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

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

• 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

• 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

Pressure

• The force exerted perpendicularly on a unit of area

• Units are Pascals (N/m2)

• Formula

• P=F/A

• P=pressureF=forceA=total surface area

• Larger area = lower 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

• 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

• 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

Buoyancy

• 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

• 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

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

• 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

• 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

• 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

• 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

• 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!!

• So Far…

• Blaise Pascal

• Evangelista Torricelli

• Eugene Bourdon

• Archimedes

• Daniel Bernoulli

• Henri Marie Coanda

• Coming Up…

• Guillaume Amontons

• John Dalton

• Joseph Gay-Lussac

• Robert Boyle

• Jacques Charles

Extra Credit????

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=pressureV=volume

• Example Problem 8-1 & 8-2

• How is this useful??

• Compressed air?

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=volumeT=temperature in Kelvin!

• How do we get Kelvin from Celsius??

• Example Problem 8-3

• Facet, page 195

TOMORROW!!

• 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