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  1. How to Use This Presentation • To View the presentation as a slideshow with effects select “View” on the menu bar and click on “Slide Show.” • To advance through the presentation, click the right-arrow key or the space bar. • From the resources slide, click on any resource to see a presentation for that resource. • From the Chapter menu screen click on any lesson to go directly to that lesson’s presentation. • You may exit the slide show at any time by pressing the Esc key.

  2. Resources Chapter Presentation Visual Concepts Sample Problems Transparencies Standardized Test Prep

  3. Chapter 8 Fluid Mechanics Table of Contents Section 1 Fluids and Buoyant Force Section 2 Fluid Pressure Section 3 Fluids in Motion

  4. 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.

  5. Section 1 Fluids and Buoyant Force Chapter 8 Defining a Fluid • A fluidis 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. • Both liquids and gases are considered fluids because they can flow and change shape. • Liquids have a definite volume; gases do not.

  6. 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.

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

  8. 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 forces can keep objects afloat.

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

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

  11. 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

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

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

  14. 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:

  15. 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.

  16. 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 = ?

  17. 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:

  18. 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.

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

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

  21. 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.

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

  23. Section 2 Fluid Pressure Chapter 8 Pressure • Pressure is 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.

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

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

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

  27. 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.

  28. 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.

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

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

  31. 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.

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

  33. Chapter 8 Standardized Test Prep Multiple Choice 1. Which of the following is the correct equation for the net force acting on a submerged object? A.Fnet = 0 B.Fnet = (robject – rfluid)gVobject C.Fnet = (rfluid – robject)gVobject D.Fnet = (rfluid + robject)gVobject

  34. Chapter 8 Standardized Test Prep Multiple Choice 1. Which of the following is the correct equation for the net force acting on a submerged object? A.Fnet = 0 B.Fnet = (robject – rfluid)gVobject C.Fnet = (rfluid – robject)gVobject D.Fnet = (rfluid + robject)gVobject

  35. Chapter 8 Standardized Test Prep Multiple Choice, continued 2. How many times greater than the lifting force must the force applied to a hydraulic lift be if the ratio of the area where pressure is applied to the lifted area is 1/7 ? F. 1/49 G. 1/7 H. 7 J. 49

  36. Chapter 8 Standardized Test Prep Multiple Choice, continued 2. How many times greater than the lifting force must the force applied to a hydraulic lift be if the ratio of the area where pressure is applied to the lifted area is 1/7 ? F. 1/49 G. 1/7 H. 7 J. 49

  37. Chapter 8 Standardized Test Prep Multiple Choice, continued 3. A typical silo on a farm has many bands wrapped around its perimeter, as shown in the figure below. Why is the spacing between successive bands smaller toward the bottom? A. to provide support for the silo’s sides above them B. to resist the increasing pressure that the grains exert with increasing depth C. to resist the increasing pressure that the atmosphere exerts with increasing depth D. to make access to smaller quantities of grain near the ground possible

  38. Chapter 8 Standardized Test Prep Multiple Choice, continued 3. A typical silo on a farm has many bands wrapped around its perimeter, as shown in the figure below. Why is the spacing between successive bands smaller toward the bottom? A. to provide support for the silo’s sides above them B. to resist the increasing pressure that the grains exert with increasing depth C. to resist the increasing pressure that the atmosphere exerts with increasing depth D. to make access to smaller quantities of grain near the ground possible

  39. Chapter 8 Standardized Test Prep Multiple Choice, continued 4. A fish rests on the bottom of a bucket of water while the bucket is being weighed. When the fish begins to swim around in the bucket, how does the reading on the scale change? F. The motion of the fish causes the scale reading to increase. G. The motion of the fish causes the scale reading to decrease. H. The buoyant force on the fish is exerted downward on the bucket, causing the scale reading to increase. J. The mass of the system, and so the scale reading, will remain unchanged.

  40. Chapter 8 Standardized Test Prep Multiple Choice, continued 4. A fish rests on the bottom of a bucket of water while the bucket is being weighed. When the fish begins to swim around in the bucket, how does the reading on the scale change? F. The motion of the fish causes the scale reading to increase. G. The motion of the fish causes the scale reading to decrease. H. The buoyant force on the fish is exerted downward on the bucket, causing the scale reading to increase. J. The mass of the system, and so the scale reading, will remain unchanged.

  41. Use the passage below to answer questions 5–6. A metal block (r = 7900 kg/m3) is connected to a spring scale by a string 5 cm in length. The block’s weight in air is recorded. A second reading is recorded when the block is placed in a tank of fluid and the surface of the fluid is 3 cm below the scale. 5. If the fluid is oil (r < 1000 kg/m3), which of the following must be true? A. The first scale reading is larger than the second reading. B. The second scale reading is larger than the first reading. C. The two scale readings are identical. D. The second scale reading is zero. Chapter 8 Standardized Test Prep Multiple Choice, continued

  42. 5. If the fluid is oil (r < 1000 kg/m3), which of the following must be true? A. The first scale reading is larger than the second reading. B. The second scale reading is larger than the first reading. C. The two scale readings are identical. D. The second scale reading is zero. Use the passage below to answer questions 5–6. A metal block (r = 7900 kg/m3) is connected to a spring scale by a string 5 cm in length. The block’s weight in air is recorded. A second reading is recorded when the block is placed in a tank of fluid and the surface of the fluid is 3 cm below the scale. Chapter 8 Standardized Test Prep Multiple Choice, continued

  43. 6. If the fluid is mercury (r = 13 600 kg/m3), which of the following must be true? F. The first scale reading is larger than the second reading. G. The second scale reading is larger than the first reading. H. The two scale readings are identical. J. The second scale reading is zero. Use the passage below to answer questions 5–6. A metal block (r = 7900 kg/m3) is connected to a spring scale by a string 5 cm in length. The block’s weight in air is recorded. A second reading is recorded when the block is placed in a tank of fluid and the surface of the fluid is 3 cm below the scale. Chapter 8 Standardized Test Prep Multiple Choice, continued

  44. 6. If the fluid is mercury (r = 13 600 kg/m3), which of the following must be true? F. The first scale reading is larger than the second reading. G. The second scale reading is larger than the first reading. H. The two scale readings are identical. J. The second scale reading is zero. Use the passage below to answer questions 5–6. A metal block (r = 7900 kg/m3) is connected to a spring scale by a string 5 cm in length. The block’s weight in air is recorded. A second reading is recorded when the block is placed in a tank of fluid and the surface of the fluid is 3 cm below the scale. Chapter 8 Standardized Test Prep Multiple Choice, continued

  45. Use the passage below to answer questions 7–8. Water near the top of a dam flows down a spillway to the base of the dam. Atmospheric pressure is identical at the top and bottom of the dam. 7. If the speed of the water at the top of the spillway is nearly 0 m/s, which of the following equations correctly describes the speed of the water at the bottom of the spillway? Chapter 8 Standardized Test Prep Multiple Choice, continued

  46. Use the passage below to answer questions 7–8. Water near the top of a dam flows down a spillway to the base of the dam. Atmospheric pressure is identical at the top and bottom of the dam. 7. If the speed of the water at the top of the spillway is nearly 0 m/s, which of the following equations correctly describes the speed of the water at the bottom of the spillway? Chapter 8 Standardized Test Prep Multiple Choice, continued

  47. Use the passage below to answer questions 7–8. Water near the top of a dam flows down a spillway to the base of the dam. Atmospheric pressure is identical at the top and bottom of the dam. 8. If the cross-sectional area of the spillway were half as large, how many times faster would the water flow out of the spillway? F. 1/4 G. 1/2 H. 2 J. 4 Chapter 8 Standardized Test Prep Multiple Choice, continued

  48. Use the passage below to answer questions 7–8. Water near the top of a dam flows down a spillway to the base of the dam. Atmospheric pressure is identical at the top and bottom of the dam. 8. If the cross-sectional area of the spillway were half as large, how many times faster would the water flow out of the spillway? F. 1/4 G. 1/2 H. 2 J. 4 Chapter 8 Standardized Test Prep Multiple Choice, continued

  49. Chapter 8 Standardized Test Prep Short Response 9. Will an ice cube float higher in water or in mercury? Explain your answer.

  50. Chapter 8 Standardized Test Prep Short Response, continued 9. Will an ice cube float higher in water or in mercury? Explain your answer. Answer: mercury; because the density of mercury is greater than that of water

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