1 / 29

Objectives

Section 1 Fluids and Buoyant Force. Chapter 8. Objectives. Define a fluid. Distinguish a gas from a liquid. Determine the magnitude of the buoyant force exerted on a floating object or a submerged object. Explain why some objects float and some objects sink.

sthilairet
Télécharger la présentation

Objectives

An Image/Link below is provided (as is) to download presentation 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. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Section 1 Fluids and Buoyant Force Chapter 8 Objectives • Definea fluid. • Distinguisha gas from a liquid. • Determinethe magnitude of the buoyant force exerted on a floating object or a submerged object. • Explainwhy some objects float and some objects sink.

  2. Section 1 Fluids and Buoyant Force Chapter 8 Defining a Fluid • Afluidis a nonsolid state of matter in which the atoms or molecules are free to move past each other, as in a gas or a liquid. • Bothliquids and gases are considered fluidsbecause they can flow and change shape. • Liquids have a definite volume; gases do not.

  3. Section 1 Fluids and Buoyant Force Chapter 8 Density and Buoyant Force • The concentration of matter of an object is called themass density. • Mass density is measured as the mass per unit volume of a substance.

  4. Section 1 Fluids and Buoyant Force Chapter 8 Mass Density

  5. Section 1 Fluids and Buoyant Force Chapter 8 Density and Buoyant Force, continued • The buoyant forceis the upward force exerted by a liquid on an object immersed in or floating on the liquid. • Buoyant forcescan keep objects afloat.

  6. Section 1 Fluids and Buoyant Force Chapter 8 Buoyant Force and Archimedes’ Principle

  7. Section 1 Fluids and Buoyant Force Chapter 8 Displaced Volume of a Fluid

  8. Section 1 Fluids and Buoyant Force Chapter 8 Density and Buoyant Force, continued • Archimedes’ principle describes the magnitude of a buoyant force. • Archimedes’ principle: Any object completely or partially submerged in a fluid experiences an upward buoyant force equal in magnitude to the weight of the fluid displaced by the object. FB = Fg (displaced fluid) = mfg magnitude of buoyant force = weight of fluid displaced

  9. Section 1 Fluids and Buoyant Force Chapter 8 Buoyant Force on Floating Objects

  10. Section 1 Fluids and Buoyant Force Chapter 8 Buoyant Force

  11. Section 1 Fluids and Buoyant Force Chapter 8 Density and Buoyant Force, continued • For a floating object, the buoyant force equals the object’s weight. • The apparent weight of a submerged object depends on the density of the object. • For an object with density rO submerged in a fluid of density rf, the buoyant force FB obeys the following ratio:

  12. Section 1 Fluids and Buoyant Force Chapter 8 Sample Problem Buoyant Force A bargain hunter purchases a “gold” crown at a flea market. After she gets home, she hangs the crown from a scale and finds its weight to be 7.84 N. She then weighs the crown while it is immersed in water, and the scale reads 6.86 N. Is the crown made of pure gold? Explain.

  13. Section 1 Fluids and Buoyant Force Chapter 8 Sample Problem, continued Buoyant Force 1. Define Given: Fg = 7.84 N apparent weight = 6.86 N rf = pwater = 1.00  103 kg/m3 Unknown: rO = ?

  14. Section 1 Fluids and Buoyant Force Chapter 8 Sample Problem, continued Buoyant Force 1. Define, continued TIP:The use of a diagram can help clarify a problem and the variables involved. In this diagram, FT,1 equals the actual weight of the crown, and FT,2 is the apparent weight of the crown when immersed in water. Diagram:

  15. Section 1 Fluids and Buoyant Force Chapter 8 Sample Problem, continued Buoyant Force 2. Plan Choose an equation or situation: Because the object is completely submerged, consider the ratio of the weight to the buoyant force.

  16. Section 1 Fluids and Buoyant Force Chapter 8 Sample Problem, continued Buoyant Force 2. Plan, continued Rearrange the equation to isolate the unknown:

  17. Section 1 Fluids and Buoyant Force Chapter 8 Sample Problem, continued Buoyant Force 3. Calculate Substitute the values into the equation and solve:

  18. Section 1 Fluids and Buoyant Force Chapter 8 Sample Problem, continued Buoyant Force 4. Evaluate From the table, the density of gold is 19.3  103 kg/m3. Because 8.0  103 kg/m3 < 19.3  103 kg/m3, the crown cannot be pure gold.

  19. Section 2 Fluid Pressure Chapter 8 Objectives • Calculatethe pressure exerted by a fluid. • Calculatehow pressure varies with depth in a fluid.

  20. Section 2 Fluid Pressure Chapter 8 Pressure • Pressureis the magnitude of the force on a surface per unit area. • Pascal’s principle states that pressure applied to a fluid in a closed container is transmitted equally to every point of the fluid and to the walls of the container.

  21. Section 2 Fluid Pressure Chapter 8 Pascal’s Principle

  22. Section 2 Fluid Pressure Chapter 8 Pressure, continued • Pressure varies with depth in a fluid. • The pressure in a fluidincreases with depth.

  23. Section 2 Fluid Pressure Chapter 8 Fluid Pressure as a Function of Depth

  24. Section 3 Fluids in Motion Chapter 8 Objectives • Examine the motion of a fluid using the continuity equation. • Recognizethe effects of Bernoulli’s principle on fluid motion.

  25. Section 3 Fluids in Motion Chapter 8 Fluid Flow • Moving fluids can exhibitlaminar(smooth) flow orturbulent(irregular) flow. • Anideal fluidis a fluid that has no internal friction or viscosity and is incompressible. • The ideal fluid model simplifies fluid-flow analysis.

  26. Section 3 Fluids in Motion Chapter 8 Characteristics of an Ideal Fluid

  27. Section 3 Fluids in Motion Chapter 8 Principles of Fluid Flow • Thecontinuity equation results from conserva-tion of mass. • Continuity equation A1v1 = A2v2 Area  speed in region 1 = area  speed in region 2

  28. Section 3 Fluids in Motion Chapter 8 Principles of Fluid Flow, continued • The speed of fluid flow depends on cross-sectional area. • Bernoulli’s principle states that the pressure in a fluid decreases as the fluid’s velocity increases.

  29. Section 3 Fluids in Motion Chapter 8 Bernoulli’s Principle

More Related