CHAPTER 8 Instruction and Intervention Support Fluid Mechanics 1 Core Instruction Chapter Resources ■ The Teacher’s Edition wrap has extensive teaching support for every lesson, including Misconception Alerts, Teach from Visuals, Demonstrations, Teaching Tips, Differentiated Instruction, and Problem Solving. ■ Several additional presentation tools are available online for every chapter, including Animated Physics features, Interactive Whiteboard activities, and Visual Concepts. Labs and Demonstrations Section Instruction Go Online for Materials Lists and Solutions Lists. ■ Textbook: Fluids and Buoyant Force ■ Lab: Buoyant Vehicle (STEM) 8.1 Animated Physics: Buoyant Force ■ Lab: Buoyancy (Open Inquiry) Visual Concepts: Fluid • Mass Density • Equation for ■ Demonstrations: Volume of Liquids and Gases • Buoyant Mass Density • Buoyant Force • Equation for Buoyant Force • Float an Egg Force • Buoyant Force on Floating Objects Teaching Visuals: Displaced Volume of a Fluid • Buoyant Force • Densities of Some Common Substances PowerPresentations ■ Textbook: Fluid Pressure ■ Demonstration: Defining Pressure 8.2 Visual Concepts: Pressure • Equation for Pressure • Pascal’s Principle • Fluid Pressure as a Function of Depth • Equation for Fluid Pressure as a Function of Depth PowerPresentations ■ Textbook: Fluids in Motion ■ Demonstrations: Fluid Flow Around a Table-Tennis Ball • 8.3 Visual Concepts: Characteristics of an Ideal Fluid • Fluid Flow Between Two Cans Equation for Continuity • Bernoulli’s Principle • Equation for Bernoulli’s Principle Teaching Visuals: The Continuity Equation and Bernoulli’s Principle PowerPresentations 268A Chapter 8 PREMIUM Content Find all of your resources online at HMDScience.com. 2 Support and Intervention 3 Specialized Support ■ Study Guide ■ Chapter Summary Audio Files Concept Maps ■ Differentiated Instruction: Below Level (TE wrap) ■ Scientific Reasoning Skill Builder Interactive Demos Sample Problem Set I Sample Problem Set II Where do I find it? PRINT DVD ONLINE Enrichment and Challenge Animated Physics ■ ■ Demonstrations (TE wrap) ■ ■ ■ Differentiated Instruction: Pre-AP (TE wrap) Labs ■ ■ ■ Take It Further: Properties of Gases (SE) Power Presentations ■ ■ ■ Take It Further: Fluid Pressure (SE) QuickLabs ■ ■ ■ ■ Timeline—Physics and Its World: 1690–1785 (SE) Teaching Visuals ■ ■ Textbook ■ ■ ■ Visual Concepts ■ ■ Interactive Demos ■ ■ Concept Maps ■ ■ Sample Problem Set I ■ ■ Sample Problem Set II ■ ■ Scientific Reasoning Skill Builder ■ ■ Assessment Study Guide ■ ■ ■ Section Quizzes Chapter Summary Audio Files ■ ■ ■ Chapter Tests A and B Differentiated Instruction (TE wrap) ■ ■ Alternative Assessment (SE) Online Assessment and Remediation ■ ExamView Banks Fluid Mechanics 268B CHAPTER 8 Chapter Overview Section 1 defines ideal fluids, calculates buoyant force, and explains why objects float or sink. Section 2 calculates pressures transferred by a fluid in a hydraulic lift and explains how hydrostatic pressure varies with depth. Section 3 introduces the equation of continuity and applies Bernoulli’s equation to solve problems of fluids in motion. About the Image This kayaker is hurtling over Rainbow Falls, on the south fork of the Tuolumne River, in northern California. The Tuolumne is a favorite river among advanced kayakers and rafters, prized for its exciting rapids and waterfalls. Kayakers know that if their weight (Fg) exceeds the upward, buoyant force (FB) that causes them to float, they are sunk—literally! For an object, such as a kayak, that is immersed in a fluid, buoyant force equals the weight of the fluid that the object FB displaces. Buoyant force causes a Fg kayak to pop to the surface after a plunge down a waterfall. (bg) ©David Madison/Getty Images Lab 268Preview The following investigations support the DEMONSTRATIONS concepts presented in this chapter. Untitled-282 268 Volume of Liquids and Gases 5/12/2011 4:28:35 AM LABS Buoyant Force Buoyant Vehicle (STEM) Float an Egg Buoyancy (Open Inquiry) Defining Pressure Fluid Flow Around a Table-Tennis Ball Fluid Flow Between Two Cans 268 Chapter 8 CHAPTER 8 SECTION 1 Fluids and Buoyant Force SECTION 2 Focus and Motivate Fluid Fluid Pressure SECTION 3 Activate Prior Fluids in Motion Knowledge Mechanics KNowlEDGE TO REVIEW • Forces can cause changes in an object’s motion or in its shape. Why It Matters • Energy can be kinetic energy or Many kinds of hydraulic devices, such as the potential energy. brakes in a car and the • In the absence of friction, the total lifts that move heavy equipment, make use of mechanical energy of a system is the properties of fluids. constant. The total mass of a closed An understanding of system is constant. the properties of fluids is needed to design such devices. ITEMS TO PROBE • Operational understanding of the concepts of area and volume: Ask students to compare the volume of containers of different shapes (with approximately the same capacity). • Ability to relate density, mass, and volume in a meaningful way: Ask students to calculate m, given ρ and V, using correct units. ONLINE Physics HMDScience.com ONLINE LABS Buoyant Vehicle PREMIUM Buoyancy CONTENT Physics HMDScience.com Buoyant Force (bg) ©David Madison/Getty Images Why It Matters 269 CONNECTING TO HISTORY in or floated on a fluid, its weight decreased. He observed that the magnitude of decrease Untitled-282 269 The concept of buoyancy is a phenomenon 5/12/2011 4:28:46 AM that drew scholars’ attention from early days in the weight of each object is equal to the of civilization. People wondered how a large weight of the amount of the liquid that is ship could float while a small metal box would displaced. sink to the bottom of the sea. The Greek After briefly discussing this history with physicist Archimedes answered this question students, ask them how Archimedes was able for the first time in 276 BCE. He carried out to use this observation to weigh objects while numerous experiments with floating and they were immersed in water. Was he making a sinking objects. In every experiment, he direct measurement or an indirect noticed that when an object was immersed measurement? Fluid Mechanics 269 SECTION 1 SECTION 1 Objectives Plan and Prepare Define a fluid. Fluids and Buoyant Distinguish a gas from a liquid. Preview Vocabulary Determine the magnitude of the Force Visual Vocabulary Hold up any solid buoyant force exerted on a object and ask students whether it is floating object or a submerged Key Terms object. fluid mass density buoyant force considered a fluid, and if not, why not. Then pour water from one container to Explain why some objects float and some objects sink. Defining a Fluid another. Ask students whether water is Matter is normally classified as being in one of three states—solid, liquid, considered a fluid, and if so, why? Hold or gaseous. Up to this point, this book’s discussion of motion and the up sealed bottles of other fluids, such as causes of motion has dealt primarily with the behavior of solid objects. shampoo, honey, and juice. Tilt them This chapter concerns the mechanics of liquids and gases. back and forth. Ask students what they Figure 1.1(a) is a photo of a liquid; Figure 1.1(b) shows an example of a gas. Pause for a moment and see if you can identify a common trait see happening in the bottles, and relate between them. One property they have in common is the ability to flow the behavior of the liquid to the and to alter their shape in the process. Materials that exhibit these definition of the term fluid. fluid a nonsolid state of matter in properties are called fluids. Solid objects are not considered to be fluids which the atoms or molecules are free because they cannot flow and therefore have a definite shape. to move past each other, as in a gas or a liquid Liquids have a definite volume; gases do not. Teach Even though both gases and liquids are fluids, there is a difference between them: One has a definite volume, and the other does not. Liquids, like solids, have a definite volume, but unlike solids, they do not Demonstration have a definite shape. Imagine filling the tank of a lawn mower with gasoline. The gasoline, a liquid, changes its shape from that of its original container to that of the tank. If there is a gallon of gasoline in the VOLUME OF LIQUIDS AND GASES container before you pour, there will be a gallon in the tank after you Purpose Demonstrate that, unlike gases, pour. Gases, on the other hand, have neither a definite volume nor a liquids have a definite volume and definite shape. When a gas is poured from a smaller container into a larger one, the gas not only changes its shape to fit the new container but cannot be significantly compressed. also spreads out and changes its volume within the container. Materials large syringe, large eyedropper or turkey baster (a) (b) FIGURE 1.1 Procedure Pull the piston of the syringe to half the tube’s length, letting air into Fluids Both (a) liquids and (b) gases are considered fluids because they can the syringe. Hold your finger tightly over flow and change shape. the opening and pull the piston back as far as possible. Read the volume of air inside the syringe. Without removing your finger, push the piston in as far as possible. Have a student record the air ©Richard Megna/Fundamental York New Photographs, volume on the board for each case. Point out that no air has been let into or Differentiated270 Chapter 8 Instruction out of the syringe tube, but the same amount of air occupies all the space. BELOW LEVEL Next, fill the syringe halfway with water, Untitled-36If you 270 ask students for examples of fluids, they 5/9/2011 10:05:11 AM and repeat the demonstration. are most likely to mention water, milk, juice, Cover the opening of the eyedropper and soda, all of which are liquids. They may and squeeze the bulb to show that the not think to include any gases, such as oxygen volume of air in the bulb and pipe can or carbon dioxide.