HSTP ch07.ppt (Read-Only) · Fluids Exert Pressure • A fluid is any material that can flow and...

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Chapter Presentation

Transparencies

Image and Math Focus Bank

Bellringers

Standardized Test Prep

Visual Concepts

Resources



Table of Contents

Section 1 Fluids and Pressure Section 2 Buoyant Force Section 3 Fluids and Motion

Chapter 7 Forces in Fluids



Section 1 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 journal to explain why air rushes out of a hole in a tire.

Chapter 7




Objectives

•  Describe how fluids exert pressure. •  Analyze how atmospheric pressure varies with depth.

•  Explain how depth and density affect water pressure.

•  Give examples of fluids flowing from high to low pressure.

Chapter 7



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, which is the amount of force exerted per unit area of a surface.

Chapter 7 Section 1 Fluids and Pressure



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.





Pressure Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key.

Visual Concept




•  Calculating Pressure Pressure can be calculated by using the following equation:


pressure = force

area

•  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).



Pressure, Force, and Area

Chapter 7

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Chapter 7


•  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.



Atmospheric Pressure

•  The atmosphere is the thin layer of nitrogen, oxygen, and other gases that surrounds Earth.

•  Atmospheric pressure is the pressure caused by the weight of the atmosphere.

•  Atmospheric pressure is exerted on everything on Earth, including you.

Chapter 7




Atmospheric Pressure, continued

•  The air inside this balloon exerts pressure that keeps the balloon inflated against atmospheric pressure.





•  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.






•  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.



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.




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 Breathing The next slide shows how exhaling causes fluids to flow from high to low pressure.







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.




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 journal about why an aircraft carrier, which weighs thousands of tons, does not sink.

Chapter 7 Section 2 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.




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.




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.




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.




Weight Versus Buoyant Force, continued

Chapter 7

•  Will an object sink or float? That depends on the whether the buoyant force is less than or equal to the object’s weight.

Section 2 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



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.




Finding Density




Changing Overall Density

•  Changing Shape The 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.







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.







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.





Swim Bladder Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key.

Visual Concept



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.

Chapter 7 Section 3 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.




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.




Factors That Affect Flight

•  Thrust and Lift Thrust is the forward force produced by a plane’s engine. Lift is 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.







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.







Drag and Motion in Fluids

Chapter 7

•  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.

Section 3 Fluids and Motion



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.



Pascal’s Principle, continued


•  Because of Pascal’s principle, the touch of a foot can stop tons of moving metal.



Forces in Fluids

Concept Map

Use the terms below to complete the concept map on the next slide.

Chapter 7

depth density water pressure pressure

fluids water atmospheric pressure









End of Chapter 7 Show



Reading

Read each of the passages. Then, answer the questions that follow each passage.

Chapter 7 Standardized Test Preparation



Passage 1 The 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




Passage 1, continued A revolutionary new undersea vessel, Deep Flight, has a hull made of an extremely strong ceramic material that can withstand such pressure. Although Deep Flight has not made it to the bottom of the Mariana Trench, some scientists think this type of undersea vessel will one day be used routinely to explore the ocean floor.




1. What is the meaning of the word revolutionary in this passage?

A strange

B overthrowing the government

C radically different

D disgusting




1. What is the meaning of the word revolutionary in this passage?

A strange

B overthrowing the government

C radically different

D disgusting




2. Based on the name of the undersea vessel described in this passage, what does the vessel look like?

F a robot

G a house

H a car

I an airplane




2. Based on the name of the undersea vessel described in this passage, what does the vessel look like?

F a robot

G a house

H a car

I an airplane




3. Based on the passage, which of the following statements is a fact?

A Scientists hope to fly Deep Flight to the top of Mount Everest.

B Deep Flight can withstand very high pressures.

C Scientists cannot explore the ocean without using Deep Flight.

D Deep Flight has gone to the bottom of the Mariana Trench a dozen times.




3. Based on the passage, which of the following statements is a fact?

A Scientists hope to fly Deep Flight to the top of Mount Everest.

B Deep Flight can withstand very high pressures.

C Scientists cannot explore the ocean without using Deep Flight.

D Deep Flight has gone to the bottom of the Mariana Trench a dozen times.




Passage 2 Buoyancy is an object’s ability to float. An object will float if the water it displaces has a mass greater than the object’s mass. It will sink if the water it displaces has a mass less than its own mass. But if an object displaces its own mass in water, it will neither float nor sink. Instead, it will remain suspended in the water because of what is called neutral buoyancy. Continued on the next slide




Passage 2, continued A goldfish has neutral buoyancy. A goldfish has a sac in its body called a swim bladder. Gases from blood vessels can diffuse into and out of the swim bladder. When the goldfish needs to rise in the water, for example, gases diffuse into the swim bladder and cause it to inflate. The swim bladder helps the goldfish maintain neutral buoyancy.




1. What is the purpose of this passage?

A to explain how a goldfish maintains neutral buoyancy

B to explain how to change the buoyancy of an object

C to convince people to buy goldfish

D to describe objects that float and sink




1. What is the purpose of this passage?

A to explain how a goldfish maintains neutral buoyancy

B to explain how to change the buoyancy of an object

C to convince people to buy goldfish

D to describe objects that float and sink




2. What is the meaning of the word suspended in this passage?

F not allowed to attend school

G stopped for a period of time

H weighed down

I supported from sinking




2. What is the meaning of the word suspended in this passage?

F not allowed to attend school

G stopped for a period of time

H weighed down

I supported from sinking




3. What is buoyancy?

A a sac in a goldfish’s body

B the ability to float

C the mass of an object

D an inflated balloon




3. What is buoyancy?

A a sac in a goldfish’s body

B the ability to float

C the mass of an object

D an inflated balloon




Interpreting Graphics

The graph below shows the water pressure measured by a scientist at different depths in the ocean. Use the graph below to answer the questions that follow.




1. What is the pressure on the object when it is 100 m underwater?

A 1.0 MPa

B 1.1 MPa

C 1.5 MPa

D 2.0 MPa




1. What is the pressure on the object when it is 100 m underwater?

A 1.0 MPa

B 1.1 MPa

C 1.5 MPa

D 2.0 MPa




2. Based on the data in the graph, which of the following is the best estimate of the pressure at 250 m below the surface of the ocean?

F 1.7 MPa

G 2.2 MPa

H 2.6 MPa

I 5.0 MPa




2. Based on the data in the graph, which of the following is the best estimate of the pressure at 250 m below the surface of the ocean?

F 1.7 MPa

G 2.2 MPa

H 2.6 MPa

I 5.0 MPa




3. Which of the following statements best describes the relationship between the water pressure on an object and the depth of the object in the ocean?

A Water pressure increases as the depth increases.

B Water pressure decreases as the depth increases.

C Water pressure does not change as the depth increases.

D Water pressure has no predictable relationship to the depth.




3. Which of the following statements best describes the relationship between the water pressure on an object and the depth of the object in the ocean?

A Water pressure increases as the depth increases.

B Water pressure decreases as the depth increases.

C Water pressure does not change as the depth increases.

D Water pressure has no predictable relationship to the depth.




Math

Read each question, and choose the best answer.




1. Anna-Marie has a coil of wire. She uses a balance to find that the wire has a mass of 17.8 g. She uses water displacement to find that the volume of the wire is 2.0 cm3 . Density is equal to mass divided by volume. What is the density of the wire?

A 0.11 g/cm3

B 8.9 g/cm3

C 19.8 g/cm3

D 35.6 g/cm3




1. Anna-Marie has a coil of wire. She uses a balance to find that the wire has a mass of 17.8 g. She uses water displacement to find that the volume of the wire is 2.0 cm3 . Density is equal to mass divided by volume. What is the density of the wire?

A 0.11 g/cm3

B 8.9 g/cm3

C 19.8 g/cm3

D 35.6 g/cm3




2. Hussain rode his bike 30 km this weekend. What is this distance expressed in meters?

F 0.3 m

G 300 m

H 30,000 m

I 300,000 m




2. Hussain rode his bike 30 km this weekend. What is this distance expressed in meters?

F 0.3 m

G 300 m

H 30,000 m

I 300,000 m




3. Olivia purchased 21 tubes of oil paint at $3.95 per tube, which includes tax. What was the total cost of the 21 tubes of paint?

A $65.15

B $82.95

C $89.10

D $93.50




3. Olivia purchased 21 tubes of oil paint at $3.95 per tube, which includes tax. What was the total cost of the 21 tubes of paint?

A $65.15

B $82.95

C $89.10

D $93.50




4. Javi filled a container halfway full with water. The container measures 2 m wide, 3 m long, and 1 m high. How many cubic meters of water are in the container?

F 2 m3

G 3 m3

H 5 m3

I 6 m3




4. Javi filled a container halfway full with water. The container measures 2 m wide, 3 m long, and 1 m high. How many cubic meters of water are in the container?

F 2 m3

G 3 m3

H 5 m3

I 6 m3




5. Pressure is equal to force divided by area. Jenny pushes a door with a force of 12 N. The area of her hand is 96 cm2. What is the pressure exerted by Jenny’s hand on the door?

A 0.125 N/cm

B 0.125 N/cm2

C 8 N/cm

D 8 N/cm2




5. Pressure is equal to force divided by area. Jenny pushes a door with a force of 12 N. The area of her hand is 96 cm2. What is the pressure exerted by Jenny’s hand on the door?

A 0.125 N/cm

B 0.125 N/cm2

C 8 N/cm

D 8 N/cm2







Chapter 7

The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.





HSTP ch07.ppt (Read-Only) · Fluids Exert Pressure • A fluid is any material that can flow and...

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