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UNIT 2 - MECHANICS

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

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  1. 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 • 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: • 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 • 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

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