How to Use This Presentation

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 Bellringers Chapter Presentation Transparencies Standardized Test Prep Image and Math Focus Bank CNN Videos Visual Concepts

3. Forces in Fluids Chapter 7 Table of Contents Section 1 Fluids and Pressure Section 2 Buoyant Force Section 3 Fluids and Motion

4. Chapter 7 Section1 Fluids and Pressure Bellringer Imagine the following situation: One afternoon, you go outside to find your younger sister standing by her bike with a nail in her hand. The bike has a flat tire. She wants to know why the air came out of the tire when she pulled the nail out. Write a few sentences in you science journalto explain why air rushes out of a hole in a tire.

5. Chapter 7 Section1 Fluids and Pressure Objectives • Describe how fluids exert pressure. • Analyze how atmospheric pressure varies with depth. • Explain how depth and density affect water pressure. • Giveexamples of fluids flowing from high to low pressure.

6. Chapter 7 Section1 Fluids and Pressure Fluids Exert Pressure • A fluid is any material that can flow and that takes the shape of its container. Fluids include liquids and gases. • All fluids exert pressure,whichis the amount of force exerted per unit area of a surface.

7. Section1 Fluids and Pressure Chapter 7 Fluids Exert Pressure, continued • In the image below, the force of the air particles hitting the inner surface of the tire creates pressure, which keeps the tire inflated.

8. Chapter 7 Section1 Fluids and Pressure Pressure Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key. Visual Concept

9. force pressure = area Chapter 7 Section1 Fluids and Pressure Fluids Exert Pressure, continued • Calculating Pressure Pressure can be calculated by using the following equation: • The SI unit for pressure is the pascal. One pascal (1 Pa) is the force of one newton exerted over an area of one square meter (1 N/m2).

10. Section1 Fluids and Pressure Chapter 7 Pressure, Force, and Area

11. Section1 Fluids and Pressure Chapter 7 Fluids Exert Pressure, continued • Pressure and Bubbles Soap bubbles get rounder as they get bigger because fluids exert pressure evenly in all directions. • Since air is a fluid, adding air to an air bubble causes it to expand in all directions at once.

12. Section1 Fluids and Pressure Chapter 7 Atmospheric Pressure • The atmosphere is the thin layer of nitrogen, oxygen, and other gases that surrounds Earth. • Atmospheric pressureis the pressure caused by the weight of the atmosphere. • Atmospheric pressure is exerted on everything on Earth, including you.

13. Section1 Fluids and Pressure Chapter 7 Atmospheric Pressure, continued • The air inside this balloon exerts pressure that keeps the balloon inflated against atmospheric pressure.

14. Section1 Fluids and Pressure Chapter 7 Atmospheric Pressure, continued • Variation of Atmospheric Pressure The atmosphere stretches about 150 km above the Earth’s surface, but about 80% of the atmosphere’s gases are found within 10 km. At the top of the atmosphere, pressure is almost nonexistent. • Atmospheric Pressure and Depth As you travel through the atmosphere, atmospheric pressure changes. The further down through the atmosphere you go, the greater the pressure is.

15. Chapter 7 Section1 Fluids and Pressure Atmospheric Pressure, continued • Pressure Changes and Your Body If you travel to higher or lower points in the atmosphere, the fluids in your body have to adjust to maintain equal pressure. • You may have experienced this adjustment is your ears have “popped” when you were in a plane taking off or in a car traveling down a steep mountain road.

16. Chapter 7 Section1 Fluids and Pressure Water Pressure • Water is a fluid. So, it exerts pressure like the atmosphere does. • Water Pressure and Depth Like atmospheric pressure, water pressure depends on depth. • Density Makes a Difference Because water is more dense than air, a certain volume of water has more mass—and weighs more—than the same volume of air. Water exerts more pressure than air.

17. Section1 Fluids and Pressure Chapter 7 Pressure Differences and Fluid Flow • Just by drinking through a straw you can observe an important property of fluids: Fluids flow from areas of high pressure to areas of low pressure. • Pressure Difference and BreathingThe next slide shows how exhaling causes fluids to flow from high to low pressure.

18. Chapter 7 Section1 Fluids and Pressure

19. Section1 Fluids and Pressure Chapter 7 Pressure Differences and Fluid Flow, continued • Pressure Differences and Tornadoes The air pressure inside a tornado is very low. Because the air pressure outside of the tornado is higher than the pressure inside, air rushes into the tornado. • The rushing air causes the tornado to be like a giant vacuum cleaner.

20. Chapter 7 Section2 Buoyant Force Bellringer • Identify which of the following objects will float in water: a rock, an orange, a screw, a quarter, a candle, a plastic-foam “peanut,” and a chalkboard eraser. • Write a hypothesis in your science journalabout why an aircraft carrier, which weighs thousands of tons, does not sink.

21. Chapter 7 Section2 Buoyant Force Objectives • Explain the relationship between fluid pressure and buoyant force. • Predict whether an object will float or sink in a fluid. • Analyze the role of density in an object’s ability to float. • Explain how the overall density of an object can be changed.

22. Section2 Buoyant Force Chapter 7 Buoyant Force and Fluid Pressure • Buoyant force is the upward force that keeps an object immersed in or floating on a liquid. • Determining Buoyant Force Archimedes’ principle states that the buoyant force on an object is an upward force equal to the weight of the fluid that the object takes the place of, or displaces.

23. Section2 Buoyant Force Chapter 7 Buoyant Force and Fluid Pressure, continued • There is more pressure at the bottom of an object because pressure increases with depth. This results in an upward buoyant force on the object.

24. Section2 Buoyant Force Chapter 7 Weight Versus Buoyant Force • Sinking An object in a fluid will sink if its weight is greater than the buoyant force. • Floating An object will float only when the buoyant force on the object is equal to the object’s weight. • Buoying Up When the buoyant force on an object is greater than the object’s weight, the object is buoyed up (pushed up) in water.

25. Section2 Buoyant Force Chapter 7 Weight Versus Buoyant Force, continued • Will an object sink or float? That depends on the whether the buoyant force is less than or equal to the object’s weight.

26. Chapter 7 Section2 Buoyant Force Buoyant Force on Floating Objects Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key. Visual Concept

27. Section2 Buoyant Force Chapter 7 Floating, Sinking, and Density • More Dense Than Air Ice floats on water because it is less dense than water. Ice, like most substances, is more dense than air. So, ice does not float in air. • Less Dense Than Air One substance that is less dense than air is helium gas. A given volume of helium displaces an equal volume of air that is much heavier than itself. So, helium floats in air.

28. Section2 Buoyant Force Chapter 7 Finding Density

29. Section2 Buoyant Force Chapter 7 Changing Overall Density • Changing ShapeThe secret of how a ship floats is in the shape of the ship. Ships made of steel float because their overall density is less than the density of water. • The next slide demonstrates how a ship made out of steel, which is almost 8 times denser than water, is able to float in water.

30. Chapter 7 Section2 Buoyant Force

31. Chapter 7 Section2 Buoyant Force Changing Overall Density, continued • Changing Mass A submarine is a special kind of ship that can travel both on the surface of the water and underwater. • Submarines have ballast tanks that can be opened to allow sea water to flow in. • As water is added, the submarine’s mass increases, but its volume stays the same.

32. Chapter 7 Section2 Buoyant Force

33. Chapter 7 Section2 Buoyant Force Changing Overall Density, continued • Changing Volume Like a submarine, some fish adjust their overall density to stay at a certain depth in the water. • Most bony fishes have an organ called a swim bladder which helps them change volume.

34. Chapter 7 Section2 Buoyant Force Swim Bladder Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key. Visual Concept

35. Chapter 7 Section3 Fluids and Motion Bellringer • You have been asked to design two kites. One kite will be flown in areas where there is almost always a good breeze. The other kite will be flown in areas with very little wind. What differences in design and materials are there between your two kites? • Record your designs in your science journal.

36. Chapter 7 Section3 Fluids and Motion Objectives • Describe the relationship between pressure and fluid speed. • Analyze the roles of lift, thrust, and wing size in flight. • Explain Pascal’s principle. • Describe drag, and explain how it affects lift.

37. Chapter 7 Section3 Fluids and Motion Fluid Speed and Pressure • Bernoulli’s principle states that as the speed of a moving fluid increases, the fluid’s pressure decreases. • Science in a Sink A table-tennis ball is attached to a string and swung into a stream of water, where it is held. Because the water is moving faster than air, the ball is pushed by the higher pressure of the air into an area of reduced pressure—the water stream.

38. Chapter 7 Section3 Fluids and Motion Factors That Affect Flight • Thrust and Lift Thrust is the forward force produced by a plane’s engine. Liftis the upward force on the wing as it moves through the air. • Wing Size, Speed, and Lift Smaller wings keep a plane’s weight low, which also helps it move faster. • Bernoulli and Birds A small bird must flap its small wings at a fast pace to stay in the air, but a large bird flaps less.

39. Chapter 7 Section3 Fluids and Motion

40. Section3 Fluids and Motion Chapter 7 Factors That Affect Flight, continued • Bernoulli and Baseball The next slide shows how a baseball pitcher can take advantage of Bernoulli’s principle to throw a curveball.

41. Chapter 7 Section3 Fluids and Motion

42. Section3 Fluids and Motion Chapter 7 Drag and Motion in Fluids • Drag is the force that opposes or restricts motion in a fluid. It is a force that is parallel to the velocity of the flow. • Drag is usually caused by an irregular flow of air, known as turbulence. • Turbulence and Lift Lift is often reduced when turbulence causes drag.

43. Section3 Fluids and Motion Chapter 7 Pascal’s Principle • What Is Pascal’s Principle? Pascal’s principle states that a change in pressure at any point in an enclosed fluid will be transmitted equally to all parts of that fluid. • Pascal’s Principle and Motion Hydraulic devices use Pascal’s principle to move or lift objects. Liquids are used in hydraulic devices because liquids cannot be easily compressed into a smaller space.

44. Chapter 7 Section3 Fluids and Motion Pascal’s Principle, continued • Because of Pascal’s principle, the touch of a foot can stop tons of moving metal.

45. Chapter 7 Forces in Fluids Concept Map Use the terms below to complete the concept map on the next slide.

46. Chapter 7 Concept Map

47. Chapter 7 Concept Map

48. End of Chapter 7 Show

49. Standardized Test Preparation Chapter 7 Reading Read each of the passages. Then, answer the questions that follow each passage.

50. Standardized Test Preparation Chapter 7 Passage 1The Mariana Trench is about 11 km deep—that’s deep enough to swallow Mount Everest, the tallest mountain in the world. Fewer than a dozen undersea vessels have ever ventured this deep into the ocean. Why? Water exerts tremendous pressure at this depth. Continued on the next slide