Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley PowerPoint ® Lectures for University Physics, Twelfth Edition – Hugh D. Young and Roger A. Freedman Lectures by James Pazun Chapter 14 Fluid Mechanics

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Goals for Chapter 14 To study density and pressure To consider pressures in a fluid at rest To shout “Eureka” with Archimedes and overview buoyancy To turn our attention to fluids in motion and calculate the effects of changing openings, height, density, pressure, and velocity

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Introduction Submerging bath toys and watching them pop back up to the surface is an experience with Archimedes Principle. Fish move through water with little effort and their motion is smooth. Consider the shark at right … it must keep moving for its gills to operate properly.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Density does not depend on the size of the object Density is a measure of how much mass occupies a given volume. Refer to Example 14.1 and Table 14.1 (on the next slide) to assist you. Density values are sometimes divided by the density of water to be tabulated as the unit less quantity, specific gravity.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Densities of common substances—Table 14.1

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley The pressure in a fluid Pressure in a fluid is force per unit area. The Pascal is the given SI unit for pressure. Refer to Figures 14.3 and Consider Example Values to remember for atmospheric pressure appear near the bottom of page 458.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Pressure, depth, and Pascal’s Law Pressure is everywhere equal in a uniform fluid of equal depth. Consider Figure 14.7 and a practical application in Figure 14.8.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Finding absolute and gauge pressure Pressure from the fluid and pressure from the air above it are determined separately and may or may not be combined. Refer to Example 14.3 and Figure 14.9.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley There are many clever ways to measure pressure Refer to Figure Follow Example 14.4.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Measuring the density of a liquid Have you ever seen the barometers made from glass spheres filled with various densities of liquid? This is their driving science. Refer to Figure

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Buoyancy and Archimedes Principle The buoyant force is equal to the weight of the displaced fluid. Refer to Figure

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Buoyancy and Archimedes Principle II Consider Example Refer to Figure as you read Example 14.5.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Surface tension How is it that water striders can walk on water (although they are more dense than the water)? Refer to Figure for the water strider and then Figures and to see what’s occurring from a molecular perspective.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Fluid flow I The flow lines at left in Figure are laminar. The flow at the top of Figure is turbulent.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Fluid flow II The incompressibility of fluids allows calculations to be made even as pipes change. Refer to Figure as you consider Example 14.6.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Bernoulli’s equation Bernoulli’s equation allows the user to consider all variables that might be changing in an ideal fluid. Refer to Figure Consider Problem-Solving Strategy 14.1.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Water pressure in a home (Bernoulli’s Principle II) Consider Example 14.7.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Speed of efflux (Bernoulli’s Equation III) Refer to Example 14.8.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley The Venturi meter (Bernoulli’s Equation IV) Consider Example 14.9.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Lift on an airplane wing The first time I saw lift from a flowing fluid, a man was holding a Ping-Pong ball in a funnel while blowing out. A wonderful demonstration to go with the lift is by blowing across the top of a sheet of paper. Refer to Conceptual Example

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley Viscosity and turbulence—Figures 14.28, When we cease to treat fluids as ideal, molecules can attract or repel one another—they can interact with container walls and the result is turbulence.

Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley A curve ball (Bernoulli’s equation applied to sports) Bernoulli’s equation allows us to explain why a curve ball would curve, and why a slider turns downward. Consider Figure