1. CHAPTER 8 - FLUID MECHANICS
UNIT 2 - MECHANICS
CHAPTER 8 - FLUID MECHANICS

2. 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

3. 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

4. Pressure 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

5. 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??

6. 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

7. Pressure Instruments Evangelista Torricelli Aneroid barometer Gauges
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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. Chapter 8C – Gas Laws Objectives: Assignment: Section Review, page 194
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

16. 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????

17. 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?

18. 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

19. TOMORROW!! Vocabulary Quiz Complete Chapter Review in Class
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