Focus on California 8th Grade Physical Science Textbook Chapter 11 Forces in Fluids

11 31 muse ( Ranges in hurls lot this Students know when the forces on an are unbalanced . the claim will change in ( Um . WI up . slow down , no ) a All a Cora in a fluid . A a bash Io ( amend a . Students know the buoyant lam on an in a fluid is an upward lone equal to lhe weight of the mud me clam has know how in an will float ow is made by asking meaningful questions and As a basis this comma ! and tho canton ! in other strands . awn and . Students will Plan awd a to In ! a . variable and ( in as lest Apply relation a missing quantity In I , given me two remaining ( weed . four area . volume may height ) Forces In Fluids The an pushing or a hang glider ) lu Hall 410

' Forces in Fluids How can you predict if an object will sink or float in a fluid ?

Check What You Know You dive into a pool wearing a life vest . Wearing the vest makes you bigger and makes you weigh more . So why do you float ?

411 The images shown here represent some of the Key Terms in this chapter . You can use this vocabulary skill to help you understand the meaning of some Key Terms in this chapter . Identify Multiple Meanings Some familiar words have more than one meaning . Words you use every day may have different meanings in science , Look at the different meanings of the words below . Word Everyday Meaning Scientific Meaning A liquid , A substance that can easily Example It good for your health a gas or a liquid to drink plenty of fluids every day . Example like water , air is a fluid To use power to make someone ri A push or a pull exerted on an do something object Example She had to herself Example You exert when to get up early . you open and close a door . II A feeling of being pushed to The force exerted on a surface do things divided by the total area over Example Students may feel which the force is exerted pressure from adults to do well Example When air leaks from a on tests . tire . the pressure is reduced and the tire becomes soft . Apply IQ ! gas increases . barometer .

Chapter 11 Vocabulary Section I ( pressure Section ( page am density principle am am Pascal system Section ( page my principle Vocabulary Web ( ode 11 413 Many parts of a textbook are organized by sequence . Sequence is the order in which a series of events occurs . Sometimes the text uses signal words , such as after . next . then . and to show sequence . Look for the signal words in the paragraph below . The was the largest ship . A few clays into its ! voyage , the struck an . iceberg cut a ring hole in the hull . aller . lhe hull to fill with water . Then the bow slipped under water and the Titanic in two . Titanic sank In the tom of the Atlantic Ocean . A flowchart can help you understand the sequencer To make a flowchart , write each step in a box . Place the boxes in order . The Titanic The manic struck an iceberg . The iceberg cut a long hole in the hull The hull began to fill with water . Apply It ! In your notebook , copy the flowchart . Then add the next steps . As you read Section , create a showing how pressure is transmitted in a fluid . As you read Section , create a flowchart on how an atomizer works .

Standards Investigation Staying Afloat Why does a heavy boat sink ?

in this investigation , you will design and build a boat that can float in water and carry cargo . You will find out what forces in fluids make an object sink or float . Your Goal To ( a boat that ( an in water and ( any cargo Your boat must be made of metal only support a cargo of 50 pennies without allowing any water to enter for at least 10 seconds travel at least meters be built following the safety guidelines in Appendix A Plan Before you design your boat , think about the shape of real ships Preview the chapter to lind out what makes an object float . Then look for simple metal that you ( an form into a boat , Compare different materials and designs to build the boat that best fits the goals listed above . After your teacher approves your design , build your boat and test it . 11 415

000 Fo Students know how Io predict an omen WI float or sink . Apply to a In a expression , gwen the two terms ( speed density , lane pressure area . volume area height ) What does pressure depend on ?

How do exert pressure ?

How does fluid pressure orange with and depth ?

Key pressure ' barometer pressure on snow 416 Pressure , Standards Wa Up Does Water Push Back ?

Fill a large sunk water . Drop a deflated balloon into the water and note what happens . Now fill the balloon with air and push the balloon into the water . Note what happens when you let go of the balloon . Think Over Drawing Compare your observations in Steps and . Why did an balloon an differently lrom the deflated one ?

mow the ground . You put on you out , in hand . you step outside . your loot sink snow . 13 up to your ! Imps the ol rhe mow . you . the bird docs not sink . In fact . it ' mark ! Why do you sink into snow the sparrow rests on the ?

The has to do with pressure . What Is Pressure ?

word ' i lo word . You may recall that gravity pulls you a force to your weight . Due to vour un the of ' an urea your . In words . your feet exert pressure on the ground .

Area 250 i Flaunt Pressure and Area The amount of pressure depends on the area over which a force is distributed . type would you use to keep from sinking into deep snow ?

Pressure and Area The amount of pressure you exert depends on the area over which you exert a force . The the area over which the force is distributed , the is exerted . In order to stand on snow sinking , you can change the area over which exert the force of your weight . Figure I shows that if you wear sneakers . your weight is distributed over the soles of both shoes . Yuu exert pressure over an area of only about 250 an or 30 ! and sink into the . But if you wear snowshoes . your weight is distributed over a much greater , or . Because your weight is distributed over at greater area . the exerted on the snow is much less . Like an sparrow . you can stand on the snow without sinking ! Calculating Pressure Pressure is equal In the force exerted at surface divided by the total area nver which the force is exerted . You can calculate pressure using the formula below . Force Pressure Force is measured in ( Area is measured in ( divided by area , the SI unit of is the per square meter ( This unit of pressure is also called the pascal ( Pa ) Nun Pa . It is named for the French Pascal . What is the SI unit of pressure called ?

Area The area of a surface is the number of square units that it covers . To find the area of a rectangle , multiply its length by its width . The area of the rectangle below is ( or ( Practice Problem Which has a greater area a rectangle that is 20 . or a square that is 10 to an ?

417 Hour Fluid Particles The particles that make up a move constantly in all directions When a particle collides with a surface , it exerts a on the . Relating Cause and men What will happen to the force exerted by the particles in the Inside Outside when you add more air ( to the chair ?

Card Trick . Fill a small plastic cup to the brim with water . Gently place an Index card over the top of the cup . Hold the card in place and slowly turn the cup upside down . Let go of the card . What happens ?

Without touching the card . turn the container on its side . Inferring Why does the water stay in the ( up when you turn the cup upside down ?

MI Fluid Pressure Solids such as sneakers are not the only materials that pressure . Fluids also exert pressure . A is a material that can easily . As a result . a can change shape . Liquids such as water and oil and gases such as air and helium are examples of . Understanding pressure in will help you to predict whether an object will or sink . what causes Fluid Pressure ?

Think about the tiny that make up a . Particles in a constantly mow in all directions . as shown in Figure . As they move . the particles collide with each other and with any surface that they meet . As each particle of a collides with a surface . it exerts a force on the surface . In at . all of the forces exerted by the individual particles combine to make up the pressure exerted by the . Because of particles is large , you can consider the as a whole . So . the pressure exerted by is the total force exerted by the divided by the area over which the force is exerted . Air Pressure Did you know that you live at the bottom of kilometers of ?

This . called air . is the of gases that makes up Earth atmosphere . These gases press down on everything on Earth surface . all the time . Air exerts pressure because it has mass . Each cubic of air around you has a mass of about kilogram . Because the force of gravity pulLs down on this mass of air , the air has weight , The weight of the air is the force that produces air pressure . or re .

Balanced Pressure Hold out your hand , palm up . You are holding up air . At sea level . atmospheric pressure is about Pa . The surface area of your hand is about . the weight supported by the area ofyour hand is about newtons , or about the same weight as that of a large washing machine ! How could your hand possibly support that weight and not feel it ?

In a stationary . pressure at given point is exerted equally in all directions . The weight of the atmosphere dorm not lust press down on your hand . It presses on your hand from every direction . The pressures balance each other . Balanced pressures also explain why the tremendous air pressure pushing on you from all sides does not crush you . Your body contains that exert outward pressure . For example . your lungs and sinus cavities contain air . Your cells and blood vessels contain liquids . Pressure from inside your body balances the air pressure outside your body . happens when air pressure becomes unbalanced ?

Look at Figure . When the can is full of air . the air pressure inside lhe can balances the pressure outside the can . When air is removed from the can . the unbalanced force of the outside air pressure crushes the can . How is the pressure on your hand balanced ! The can contains air . The air pressure pushing out balances the air pressure But when the air is removed from the can . there is no longer the some pressure pushing out . The greater air pressure outside the can crushes the can . A unbalanced Pressure A vacuum pump removes the air from a metal can . The unbalanced air pressure produces dramatic results in a few moments . Atmospheric Pressure The pressure of atmosphere is exerted over the entire surface of your hand . The downward pressure is the same as the upward pressure . it 11 419

Many airplanes at Atmospheric is 20 that at sea level . A ! In , Mount Everest is the point on Earth . some can read ! In . Hen . pressure I about MINI use level . heights of an . am . the air prewar Is 70 that at sea . i Web Code Variations in Fluid Pressure Have you ever felt your cars pop ' as you rode up in an elevator ?

What happens to pressure as you climb to a higher elevation or sink to a lower depth within a ?

Figure shows how sure changes depending on where you are . Atmospheric Pressure and Elevation The popping in your ears is caused by changing air pressure . At higher . there is less air above you and therefore less air sure . Atmospheric pressure decreases as your elevation increases . When the air pressure outside your body decreases , the air pressure inside also decreases . but more slowly . So . for a moment , the air pressure behind your eardrum is greater than it is in the air outside . Your body releases this pressure with a balancing the pressures . Water Pressure and Depth You experience a type of change if you dive underwater . Water pressure increases as depth increases . 50 if you dive into a body of water , pressure becomes greater as you descend . The deeper you swim , the greater the pressure you feel . Just lo below the surface , the water ' pressure on a scuba diver is double the pressure at sea level . The gulper eel live Ill below the , Pressure here is about 250 times greater than standard atmospheric . Piloted can explore as deep as In . Here , water pressure is 650 times greater than at sea level .

Front Water is a result of the weight water above at ' particular point . At greater depths , there is more water above An aneroid barometer measures A that point and more weight to support . In addition . air in the atmosphere pushes down on the water . Therefore . the total pressure at a given point beneath the water results from when atmospheric pressure the weight of water plus the weight of the air above it . In the decreases ?

deepest parts of the ocean , the pressure is more than times the air pressure you experience every day . Measuring You can measure sure with an instrument called it . Weather ers use the pressure reading front a barometer to help forecast the weather . Rapidly decreasing atmospheric pressure usually means a storm is on its way . Increasing pressure is often a sign of fair weather . The barometer you usually see hanging on wall is an aneroid barometer . Forecasters will often express the pressure in units of millimeters of mercury or inches of mercury . Those units are based on the original type of barometer . which measured how far the atmosphere pushed liquid mercury up a tube . Standard pressure at sea level may be reported as 760 ters of mercury . which is about the same as what Instrument measures atmospheric pressure ?

Assessment Vocabulary Identity Multiple Meanings a . Describing How does atmospheric pressure Use the and pressure change as you move up may from sea level ?

to help you the term pressure . ma ( change in pressure with elevation to the change in water pressure with depth . Applying ( Why must an astronaut wear at suit in space ?

Water and Fill a pot with water from the sink . Fill a sandwich bag with water at the same temperature . Seal the bag and drop it into the pot . Note what happens . Then repeat Reviewing Key Concepts . Reviewing What two factors docs pressure depend on ?

HE . Comparing and Who exerts more pressure on the woman standing in high heels with a area of , or the same woman standin in boots with at total area of ?

the pressure the exerts on the ground in both cases . How do exert pressure ?

is . Why are you crushed by the weight of the atmosphere ?

Inferring How is your body similar to the can containing air shown in Figure ?

355 the experiment with a sandwich bag filled with hot water and a sandwich bag filled with water that is just slightly above the freezing point . Describe your observations . iii iii Design Your Own Lab of Spinning Sprinklers . Problem What factors affect the speed of rotation of a lawn sprinkler ?

Skills Focus designing experiments . controlling variables What Factors Affect Spin ?

How does the size of the hole affect the number of spins made by the can ?

Propose a hypothesis and then design an experiment to test the hypothesis . Obtain your approval before carrying out your ment . Record all your data . How does the number of holes affect the number of spins made by the can ?

Propose a hypothesis and then design an experiment to test the hypothesis . Obtain your teachers approval before carrying out your Materials , empty soda can I fishing line . 30 I waterproof marker I jar or beaker ' ment . Record all your data . nails of various sizes Analyze and conclude ' th ' ow oes the hole affect the rate of spin of the can ?

PART Making a Sprinkler How does the number of holes affect the rate of spin of the can ?

Fill the jar with enough water to completely cover a soda can . Place the jar in the basin . Controlling Variables What controlled parameters did you leave in this . Bend up the tab of a can and tie the end ofa length of fishing line to it . The experiment ?

What other parameters might affect the number of spins made by the ( an ?

edge of the can opening can be sharp . Place a mark on the can to help you keep track of how many times the can spins . Using the small nail , make a hole in the side of the can about an up from the bottom . Poke the nail straight in . Then twist the nail until it makes a right angle with the radius of the can as shown in the figure above . Interpreting Data Explain the motion of the can in terms of unbalanced forces . Which of Newton three laws of motion could you use to explain the motion of the can ?

Explain . Communicating Use the results of your experiment to write a paragraph that explains why a spinning lawn sprinkler spins . Nails are sharp and should be used only to puncture the cans . Mme to Explore Some sprinkler systems use water pressure to spin . Examine one of these sprinklers to see the size , direction of spin , and number of holes . What would happen if you connected a second sprinkler to the first with another length of hose ?

If possible , try it . Submerge the can in the jar and fill the can to the top with water . Quickly lift the can with the fishing line so that it is above the water level in the jar . Practice counting how many spins the can completes in IS seconds .

Standards Students know the buoyant force on an obiect in a is an upward equal to the weight ol the the object has displaced . Students know now to ! whether an will float or sink How can you predict whether an will or sink in a what is the effect of the buoyant ?

Key Terms ' buoyant I Archimedes principle Floating and Sinking aids What Can You Measure With a Pencil ?

Stick a metal thumbtack in the eraser of an unsharpened wooden pencil . You have built a device called a hydrometer . Place the pencil in a glass of water with the eraser and tack pointing down . Note how far the pencil sinks in the water by marking the edge 01 the pencil at the water surface line with a waterproof marker . Remove the pencil from the water . Measure the length the pencil sunk in centimeters . Dissolve ol sugar into the glass at water . Try out your in this liquid . Again mark how far the pencil sinks . Then remove the pencil from the water and once again measure the length the pencil sunk in centimeters Think it Over Predicting Compare your observations in and . Predict what will happen it you use 20 spoonfuls of sugar in a glass of water . Test your prediction . in April . the departed from on its lirst rind only ' the time , it was the largest ship football long . The was also the most technologically advanced ship in existence . hull was divided into , rind it was considered to be . Yet few into the voyage . the struck an iceberg . One after another with Ims than three hours later . the bow of thi great ship slipped under the waves . As the stern rose high into the air . the ship broke in two . Both pieces ' lo the bottom Atlantic Ocean . More than at ind . The bow section of the Titanic resting on the ocean

Density The Titanic sank because of a change in its density . Recall that the density of a substance is its mass per unit volume . Mass Volume For example , one cubic centimeter ( of copper has a mass of grams . so its density is gem . One cubic meter of plastic has at mass of only about gram . So the density of plastic is about . Copper is more dense than plastic . The density of water is ID . So water is less dense than copper but mare dense than plastic . Density Comparing Densities of Figure shows eral substances and their densities . Each substance has its own density . Some liquids on top of other liquids . The stances with the greatest densities are near the bottom . object will or sink in a . An object that is more dense than the it is in sinks . An object that is less dense than the fluid on the surface . An object with a density equal to that of the at a constant ) When will an object on I sultan ?

corn oil Calculating Density The density at a substance is its mass per unit of volume . Dusky For example . a sample of liquid has a mass of 24 and a volume of 16 What is its density ?

16 . Practice Problem A piece at metal has a mass of and a volume of 15 . What is its density ?

Flame Densities of Substances Vou ( an use density to predict whether an object will sink or float when placed in a liquid . Predicting Willa rubber washer sink or in ( oil ?

Water Tar ball Glycerin I Rubber washer Corn Copper wire ! Mercury 9425 submarine rises when compressed air enters the tanks . forcing the water out . The decreased of the submarine is less than inter . OA submarine silks . until . Changing Density Changing density can explain why an object or sinks . For example . you am change the density of water by freezing it into ice . Since water expands when it , the ice occupies more space than the water . That why ice is less dense than water . But it just a bit less dense ! So most of an ice cube on the surface is the surface . You can make an object sink or in a by changing its density . Look at Figure to see how this happens to a rine . The density of a submarine increases when water its tanks . This happens because the overall mass of the submarine increases . but its volume remains the same . So the submarine will sink . To make the submarine rise in the water , the engineer pumps water out of the tanks , decreasing the mass . its density decreases . and it rises . when I rise ?

4260 Buoyancy Ships are designed to have ability to float . How is it possible that is huge ship can easily on the surface of water under certain conditions , and then in a few hours become I sunken wreck ?

To answer this question . you need to understand the buoyant force . Gravity and the Buoyant Forte If you have ever picked up an object under water . you know that it seems much lighter in water than in air . Water and other exert an upward force called the buoyant fume that acts on a submerged object . buoyant acts in the direction opposite to the force of gravity . so it makes in object feel lighter . The less dense the object is , the greater the buoyant force it experiences . As you can see in Figure , a exerts pressure on all faces of a submerged object . Since the in a increases with depth . the upward pressure on the bottom of the object is greater than the downward pressure on the top . The result is a net force acting upward on the submerged object . This is the buoyant force . Remember that the weight of a submerged object is a ward force . If an object weight is greater than the buoyant force , a net force acts downward on the object . The object will sink . If the weight of an object is equal to the buoyant force . no net force acts on the object The object will not sink . A sub merged object whose weight is equal to the buoyant force also has no net force acting on it . The object will not sink . Remember that you can also use density to explain why objects or sink . in Figure ID . the density of the is less than that of water , while the turtle density is equal to that of water . The and the turtle . The density of the lobster is greater than water . The lobster sinks . Weight weight ! Form The pressure on the bottom of submerged object greater than the pressure on the top . The result is a net force in the upward direction . Buoyant to Buoyant Force and Weight The buoyant forte works opposite the weight of an object . The forces acting on the and turtle are balanced , so they float in place , The forces on the lobster are unbalanced . Comparing and ( entrusting Why does the lobster sink ?

Sinking When the can has in it . it sinks . The volume of displaced by the can is equal to the volume ol the an . Principle principle applies to sinking and objects . Predicting If you press down on the floating can . what wilt happen to the volume of the displaced in the small beaker ?

Trip Channel School Forces in fluid Floating When the can is empty . it The volume ol displaced is equal to the volume of the submerged portion oi the un . Film ( an Displaced Archimedes Principle All objects take up space . A submerged object displaces . or takes the place of . a volume of equal to its own volume . A partly submerged object displaces a volume of equal to the ume of its submerged portion only . You can see this in Figure I Archimedes , a mathematician of ancient Greece . ered a connection between the weight ofa displaced by an object and the buoyant force acting on it . states that the buoyant force acting on a submerged object is equal to the weight of the volume of displaced by the object . Suppose your body displaces 50 liters of water in a swimming pool . The buoyant force on you will be equal to the weight of 50 liters of water . or about SOON . Submarines How can a submarine dive and ?

Since the buoyant force is equal to the weight of the displaced . the buoyant force on the submerged submarine stays the same . Changing the water level in the tanks changes the weight of the submarine . The submarine sinks when its weight is greater than the buoyant force . It rises when its weight is less than the buoyant forte . Balloons Air is a . A balloon with air is denser than the surrounding air because the air inside it is under pressure . The denser air inside makes it fall to the ground . But if the air inside the balloon is heated . it becomes less dense , and the balloon rises . You can also a balloon with helium . A helium balloon rises because helium is less dense than air . Why does I helium balloon float in air ?

El El Weight . You cam use Archimedes principle to explain why at ship on the surface . Since the buoyant force equals the weight of the displaced fluid . the buoyant force will increase if more is displaced . A large object displaces more than a small object . A buoyant force on the larger object even ifthe large object has the same weight as the small object . look at Figure . The ship hull has the same mass as the solid block of steel . but its shape causes the ship to displace a greater volume of water . According to Archimedes principle . the buoyant force is equal to the weight of the displaced water . Since a ship displaces more water than a block of steel . a greater buoyant force acts on the ship . The buoyant force acting on it is equal to its weight , and the ship on the surface . Section Vocabulary Skill identify Multiple Meanings Us the meaning to define the key term . Reviewing Key Concepts a . Defining What is density ?

Explaining How can you use the density uf an object to predict whether it will or sink in water ?

Applying Concepts Some canoes have compartments on either end that are and watertight . These canoes wo sink . even when they . Explain why . a . Explaining How does the buoyant force affect ?

How does Archimedes principle relate the buoyant force acting on tut object to the fluid the ?

696 Route 11 Floating Ship A solid block of steel sinks in water . A steel ship with the same weight floats on the surface . Assessment Calculating An object that weighs 340 un a lake . What is the weight of the displaced ?

What is the buoyant force ?

Changing Balloon Density Attach paper clips to the string of a helium balloon . Ask a family member to predict how many paper clips you will need to attach to make the balloon sink to the floor . How many paper clips can you attach and still keep the helium balloon suspended in the air ?

Explain how adding paper clips changes the overall density of the balloon .

Sink and Spill Problem How is the buoyant force acting on an obiect in a related to the weight of the the object displaces ?

Focus controlling variables , interpreting data , drawing conclusions Materials paper towels pie pan balance beaker , jar with watertight lid , about 30 mI . table salt Procedure . Preview the procedure and copy the data table into your notebook . Predict the you will lind between the buoyant force and the weight of the displaced water . Find the mass , in kilograms , of a dry paper towel and the pie pan together . To convert grams to kilograms , divide the mass in grams by . Multiply the mass by . This gives you the weight in newtons . Record it in your data table . Data Table of of in Jar Pan and A Displaced A ' Displaced and ) Towel ) 4300 . Place the beaker , with the dry paper towel under it , in the middle ot the pie pan . Fill the beaker to the very top with water . A Fill the jar about halfway with salt . The jar and salt must be able to float in water . Find the mass of the salt and the dry jar ( with its cover on ) in kilograms . Multiply the mass by . Record this weight in your data table . Gently lower the jar into the . beaker . It the jar sinks . take it out and remove some salt . Repeat Steps . and . Estimate the fraction of the jar that is . and record it . Once all ofthe displaced water has been spilled , find the total mass of the paper towel and pie pan containing the water in kilograms . Multiply the mass by and record the result in your data table . Empty the pie pan . Dry off the pan and iii . Repeat Steps through several more times . Each time till the jar with a different amount of salt . but make sure the jar still floats . Record the buoyant force for each trial in your data table . Hint when an object . the buoyant force is equal to the weight of the object . Calculate the weight of the displaced water in each case . Record it in your data table .

Analyze and conclude . Variables In each trial . the jar had a different weight . How did this affect the way that the jar ?

Interpreting Data The jar had the same ume in every trial . Why did the volume of displaced water vary ?

Drawing Conclusions What can you about the relationship between the buoyant force acting on an object and the weight of the water it displaces ?

Drawing If you put too much salt in the jar , It will sinks What can you about the buoyant force in this case ?

How can you determine the buoyant force for an object that sinks ?

Communicating Write a paragraph ing changes to the experiment that would improve the accuracy of your results . Design an Experiment How do you think your results would change it you used a liquid that is more dense or less dense than water ! Design an experiment to test your hypothesis . What liquids will you use ?

Will you need equipment other than what you used for this experiment ?

It so , what will you need ?

Obtain your teacher permission before carrying out your investigation .

! Students know the buoyant forte on an in a is an upward equal to the weight of the fluid the object has displaced . What does Pascal say about change in fluid pressure ?

How does a system work ?

Key Terms I Pas ( principle hydraulic system A sea star uses fluid pressure to move . 4310 Pascal Principle , Standards Why Does the Cartesian Diver Sink ?

I . Fill a plastic jar or bottle almost completely with water . Make a Cartesian diver by bending a plastic straw into a shape . Cut the ends so that each side is ( long . Attach the ends with a paper clip . Drop the straw in the tar , paper clip first . Attach more paper clips to the first one until the straw floats with its top about above the surface . this is the diver . Put the lid on the jar . Observe what happens when you slowly squeeze and release the jar several times . Think it Over observing Describe the behavior of the Cartesian diver . At lirst . you hesitate . but then you hold out your hand . The aquarium attendant places the sea star in your palm . You can feel till your skin . The many tiny on the underside look like suction cups . and they tickle just at hit ! The explains that the sea star has ( I of tubes containing water in its body . As the water moves around in the . it create changes in that allows the sea star to move .

Transmitting Pressure in a Fluid If you did the Standards . you may be wondering why the buoyancy of the Cartesian diver changes . Squeezing the tle made the diver sink because you increased the pressure on the water inside the bottle . The water pushed into the straw . reducing the size of the pocket of air and increasing the divers density . This happened no matter where you squeezed tle . By changing the pressure at any spot in the closed container , you transmitted pressure throughout the container . Pascal in the locus . Pascal developed it principle to explain how pressure is transmitted in a . As you know . exerts pressure on any surface it touches . For example . the colored water in each bottle shown in Figure exerts pressure on the entire surface of the . down . and sideways . What happens if you squeeze the bottle when its top is closed ?

The water has nowhere to go . so it presses harder on the inside surface of the bottle . The water pressure increases everywhere in the bottle . This is shown by the increased length of the arrows on the right in Figure 13 . Fatal principle states that pressure increases by the same amount throughout an enclosed or fluid . applied to a , the change in pressure . What is Pascal principle ! Frame 13 Pressure A liquid that till a battle exerts pressure in all directions . If you squeeze the bottle . you increase the pressure . Predicting Suppose you opened the top of the water bottle . What would happen when you squeezed the bottle ?

Why ?

9433 System A System I Force is applied to Force is Force on the larger the piston . through the fluid to piston Is multiplied . the other piston . or ( forte ' Equal areas Force Force Force Larger force Pressure Pressure Are Area Area Larger area FIGURE 14 Fiscal Principle It Work You can see Pascal principle ! at work in Figure . A hydraulic device consists of two tons one at each end of a ed tube A is like it applied to one piston increases the ' pressure equally throughout stopper that slides up and down LI tube . the fluid . By changing the area at Suppose you fill System A with water and then push down on the . The OM ?

the left piston . The increase in pressure will be transmitted multiplied . Mum mummy he to the right . to , both ) Dyed the , ui th pistons have four times , how much larger mun same surface am . they will experience the same . the am of the be Now look at System , The right has a greater surface compared to the left piston ?

Go active For Hydraulic Systems activity Weir Code 4340 area than the left piston . Suppose the area of the small piston is I square centimeter and the area of the large piston is square centimeters . The right piston has an area nine times greater than the area of the left piston . if you push down on the left piston . pressure is transmitted equally to the right piston . The force you exert on the left piston is multiplied nine times when it reaches the right piston . By changing the area of the pistons , you can multiply force by almost any amount you wish . How mom in System I ?

Hydraulic Systems Have you ever wondered how a person can stop a large car by pressing down on a little pedal ?

Or how mechanics are able to raise cars off the ground so they can repair them ?

In both cases , hydraulic systems using Pascal principle are at work . A hydraulic system uses liquids to transmit pressure and multiply force in a . A hydraulic system multiplies force by applying the force to I area . The increase in pressure is then transmitted to another part of the fluid , which pushes on it surface . Because they use fluids to pressure . hydraulic systems have few moving parts that can iam . break , or wear down . Lifts Hydraulic lift systems are used to raise cars oil the so mechanics can repair them with case . They are also used to lift the heavy ladder on it fire truck reach the upper windows of a burning building . In addition . hydraulic lifts are used to operate many pieces of heavy construction equipment such as dump trucks . snowplows , and cranes . Next time you see a construction vehicle at work . see can spot the hydraulic pistons in action . Math Algebra and Functions Analyzing Data . paring Hydraulic Lifts The graph shows the relationship between the applied force and the lifting force for two hydraulic lift . Reading Graphs Suppose a force of is applied to both lifts . Use the graph to determine the lifting force of each lift . Reading For Lift how much force must he applied to lift object ?

Interpreting Data By how much is the applied force multiplied for Lift A ?

Lift ?

Interpreting Data What does the slope of each line represent ?

Drawing Conclusions Which lift would you choose if you wanted to lift a weight of ?

Explain . Hydraulic Applied Forte ( as Haunt 15 Hydraulic Brakes The hydraulic brake system of a car multiplies the force exerted on the brake pedal . Comparing and Contrasting How does the size of the brake pedal compare with the rite of a brake pad piston ?

if ) Brake pedal Hydraulic Brakes You un you ride in a car . The brake system of car is a hydraulic system . a brake with disc down on tha brake pedal , or she pushes a small piston . The piston pressure on the brake fluid . The in through in the lines to larger pistons within the wheeLs of the car . Each of these pushes on brake pad . The pads rub against the brake disc . and the is slowed down by the lure of friction . Because the brake system multiplies force , an can stop car with only a light push on brake pedal . Section Assessment Target Reading Skill Sequence ( ironic 21 What is a hydraulic system ?

to show how is How does sy rem work ?

ill Sequencing ) HINT ol car the um steps on the ( Reviewing Key Concepts a . Reviewing tu al principle . Nah Pam he we imp lulu ' I ( pI ' ma Lil . HINT . Explaining How does Pascal In Science ( diver ?

i mu ) A i 71 ( customer asks you his brakes do not an ) dam Ii i ) lI ( In another he a ' with an area of . by how much will leak ' It ?

letter to the customer explaining why a leak the inn he ?

In the brake line caused his brakes to fail . We Section Tech Design Standards Fo Students know that when the on an are anted , the will change its velocity ( that is , it will speed up . slow down , or change direction ) How is fluid pressure related to the motion of a fluid ) What are some applications of Key Terms principle I lift Principle Standard Warm Up Does the Movement of Air Create Unbalanced Forces ?

Use your thumb and forefinger to hold a sheet of paper by the corners . Hold the paper just below your mouth . so that its edge is horizontal and the paper hangs down . Blow across the top oi the paper . Repeat this several times . blowing harder each time . Think Over Inferring On what side of the paper is the force greater ?

How do you know ?

Wilbur and Orville brought an looking ' a beach in Kitty , North lina . in fur more than it ' but ' goal ' no um had ever . They plain llI was ' than air ! They had spent year experimenting with different wing shapes and surfaces . and they had carefully studied the flight . at Kitty Hawk . Thu more them 36 and history . What did Wright ' know about that allowed them to construct the And how can the principles they him a it ! can ?

The . has to do with pressure and how a moving can an unbalanced force . on December 17 . the Wright brothers plane Flyer New for the first time 9437 Val . Pressure and Moving Fluids 30 fin in this chapter , you learned about that are not Faucet Force moving . What makes a ?

And what happens to , Held Spoon pressure when ?

the ed es of its hand , my Fluid Motion A tends to How from an area of high between your lingers . to an area . This happens . for example . on fau ( to when you sip a drink min at straw . When you start to sip , you produce a steady stream the air from the straw . This ill arm of low guru in the straw . The higher air pushing down on the happen if you the surface drink forces the drink up into . bottom of the spoon to the ' Principle In the . Swiss scientist ' hur NO ) lee ) discovered that the pressure of Repeat the test several ' moving is different than the pressure of ti at rust . principle that faster at , the pressure exerts . did the Standards , yuu saw that air moving over the paper caused the paper rise . principle explains the behavior of the paper . principle states that as the speed of in moving increases , the pressure exerted by the decreases . The air above the paper , but the air below the paper docs not . The moving air less pressure than the still air . As it mull , the still air exerts greater pressure on the bottom of the paper , creating an unbalanced force which pushes the paper up . times . use , principle ?

your observations to develop a hypothesis explaining why the spoon moved as it did . 16 Making Air Move Blowing air quickly between two cans lowers the air pressure between them . Higher pressure exerted by the still air to either side pushes the cans toward other . BIO

new 17 Airplane wing , An airplane wing is designed to modem Air moves faster an upward force for a plane In night . wing , Why ?

creating an area pressure lower above me ?

Applying Principle The Wright brothers understood principle . They used it when they built their plane . principle helps explain how planes It also helps explain how an atomizer works . why smoke rises up I chimney , and how a disk glides through the air . Objects in Flight principle is one factor that helps explain a small kite to a huge airplane . Objects can be designed so that their shapes came air to move at different speeds above and below them . If the air moves faster above the object . pressure pushes the object upward . If the air moves faster below the object . pressure pushes it downward . Because ol iLs design , the wing ' produces lift , or an upward force . Look at Figure to see the design of a wing . Both the slant and the shape of the wing are sources of lift . Because the wing is slanted . the wing forces the air downward as the plane moves . The air exerts an equal and opposite force on the wing and pushes it upward . This upward force helps an airplane to take ' The curved shape of a wing also gives an airplane lift . Because the top ofthe wing is curved , air moving over the top has a greater speed than air moving under the bottom . As result . the air moving over the top exerts less pressure than the air below . The difference in air pressure above and below the wing creates lift . Online ( cub ' For links on Visit Well Code

low pressure i The difference in pressure between la the top and bottom rectum ofthe tube draws An atomizer is an application i the perfume upward . of principle . Applying Concepts Whyis High pressure the perfume pushed up and out of the flask ?

Direction of principle can help you stand how the perfume atomizer shown in Figure 18 works . When you squeeze the rubber bulb . air moves quickly past the top of the tube . The moving air lowers the at the top of the tube . The greater pressure in the pushes the liquid up into the tube . The air stream breaks the liquid into small drops . and the liquid comes out as a . In a similar way , pressure in the carburetors of older gasoline engines push gasoline up a tube . There . the gasoline combines with air to create the mixture of air and fuel that runs the engine . Chimneys You can sit next to a enjoying a cozy thanks in part to principle . Smoke rises up the chimney partly because hot air rises . and partly because it is pushed . Wind blowing across the top of a chimney lowers the air pressure there . The higher pressure at the pushes air and smoke up the chimney . Smoke will rise faster in a blowing across the top of a chimney creates an area of low pressure . Direction of smoke The difference in air ?

ney on a windy day than on a calm day . theme and bottom of the chimney helps I I keep air moving ' upward . Result 19 Chimney Thanks in part to principle . you can enjoy an evening by a warm without the room up with smoke . Making Why does the smoke rise up the chimney ?

Flying Disks Did you ever wonder what allows a disk 20 to glide through the air ?

The upper surface of disk is ! curved like an airplane wing . principle explains me an ' uses a curved upper sulfate to that the air following the disks curved upper ( comps , surface exerts less pressure than the air beneath Contrasting How does a it . A net force acts upward on the disk . creating lift . ing the disk slightly toward you as you throw it also helps to keep it in the air . A tilled disk pushes air down . The air exerts an equal and opposite force on the disk . pushing it up . The spinning motion of a flying disk keeps it stable as it . section it Target Reading Skill Sequence to explain how an atomizer works . Reviewing Key Concepts . I . Reviewing How can you make up a straw ?

Summarizing What does say the pressure exerted by moving ?

Applying Concepts You are riding in a car an a highway when a large truck speeds by you . Explain ( ear is toward the truck . pap ?

the paper cup with one hand . With mu ?

i . Listing List four applications of principle . Explaining Why does the air above an airplane wing differ from the below it ?

How i pre difference involved in flight ?

Cause and Effect How could strung winds from hurricane blow the ' a house ?

Paper Chimney with a member , see how a chimney works by using a paper cup and a hair dryer . Cut up several small pieces of tissue and place them in the the ( up . Explain to your Family member how principle explains how the chimney works .

Technology and Tech Design ' Helicopters ' i ?

their angle . Blades Most aircraft are like off Air over the curved . majestically , glide among the clouds . and ' I land with ears . But are , give me , They can ily forward , and up and down . They can stop abruptly and hover in . In fact , can circles around other types of aircraft . Science in Action On ' lop an large blades are on up like . Air the helps ( arise upward for the as over wings helps ( amt lill for mu ! and mic lion forces as third law of , As the tilted blades push down on the air , the air upon . As the rotor spins . the reaction force pushes the body in the direction . I If not for the tail rotor , Hand Controls and Foot Pedals the body would spin too . These LO ! are connected to mam rotor . The collective control guides the helicopter up or down lhe cyclic the forward , hack ard , or sideways Tho pedals al lo the . rotate IV tight

The Aircraft of Not ?

can and land . So are nit oi clinic in ' in ward ) and . in fighting , and In people In . us lo . arc to using helicopters . Compared to an . helicopter must mun and um remain in air . is that a eq lung or large uf . Air flowing over the curved blades helps create tift . Path of air Engine eig the Impact . Identify the Need do ?

Research ( haw arc in , such I ! Yellowstone . Choose one . Make the level , location . The engine the main role ! power to spin the blades . Tail Rotor The force of the tail rotor prevents the helicopter body from spinning by pushing against the reaction force at the main rotor . Write mu are A pal . rang ( Il ( IlL In a in your why helicopter was or not the best In this . um Mote an Visit ( tom Web ( ode (

Chapter 11 Study Gu Pressure Key Concepts . The amount ol yuu ex depends on the area uver force . Fun Area I In . all of the forces by the particles lu make up the ( by the . Pressure pressure In mixes as your elevation increases , Water as increases . Key Terms ure pascal Floating and Sinking Key By comparing densities . you can predict whether an will limit ur sink in A fluid . The acts in the opposite to lhe form of , so il nuke an feel lighter . Key Terms ( um principle MOO II In object is less dense than a . it will lion in the fluid . ii an object is more dense than a fluid . it will sink in the fluid . Pascal Principle Key Concepts When ix applied to a , the in pressure is equally to all pans or the . I hydraulic system lore by applying the force to a area . The in is then In another part of the ( unlined . which pushes a larger arm . Key Terms Pascal principle system Principle ( Key . principle as the speed ul increases , the by the decreases . principle helps explain how planes . also helps how an atomizer works . why rises up A , and how disk glides through the air . Key Terms principle lift

Review and Assessment Reading Skill . Sequence ( a ' device force . Go , i For Visit Web How I Hydraulic Device works mailed to . i , Choose the letter of the best answer . If the 24 hy the total ' i a of the , you will density . litt . If yuu Ina of an by its . you also know the weight . Ill . mass . The wright ( 41 ! that limits his the same value as the ' i . Th ( that an in ' on is In all parts is known as . principle , Newton third law . The that the pressure in as the speed is ( il principle , principle lint Law . Reviewing Key terms Complete the following sentences so that your answers clearly explain the terms . you the pressure you exert on the ground . an will or ) in il ' depends on its density . hi ( is 33 ) claim is tu lift to the HINT ii buoyant force . which is . A ship is able to on the of the strait Archimedes principle . which that A 10 . All is ) partly due in , that Writing in Science News Suppose that you are a newspaper journalist on the day after the sank Write a news that tells what happened . Explain how the buoyancy of a ship is affected when it fills with water . Include information about the various forces involved . Fortes In Fluids El

Review and Assessment Checking Concepts does the ol you on the when you are ) down with the you ex when are up ?

12 . crushed by that ) 13 . do you semi lu weigh in air than you do ?

14 . In system . why is the force exerted on multiplied inn piston ?

15 . lI ) would . 16 . in air pressure at the lop of a ' than the ?

17 . Making Generalizations How dues the water at ugh . in the ?

How can you lull ?

king cally . Problem Solving You ( ol ' A In is the two thirds . 19 Developing Hypotheses ( of is pill in ' and . li ' il . Develop this . 10 . Applying Concepts One method of raising sunken ship to the is to inflate large hags ' inside its . why this ' could work , 4466 Math Practice 21 . Area The cover of textbook 18 I 12 . Find its area . 22 . Area A dollar bill about un . The mil . Which um bill ?

Applying Skills The Illustration shows an object supported by a spring scale . both in and out of water . Use the illustration to answer Questions . 23 , Inferring Why is a between the weight ( if the in air and InL , hI in water ?

24 . Calculating is the force acting on the ?

25 . Drawing What you the waiter line ?

Sta Investigation Performance Assessment your hunt to sun it due nut leak . i play the dill you tried and the . and ( uch . Then ( for class how the . Point out in classmates the you in mur .

Standards Practice at Choose the letter of the best answer . You place a block of wood into a beaker of . Why does an rise in the air ?

water and it . What can you say about the A It experiences a buoyant force because it is buoyant force on the less dense than the air , A It is equal In the block weight . The moving air above and below the wings It is less than the block weight . creates an unbalanced force that pushes the It is greater than the block weight . it is equal In the weight uf the surrounding The air pressure above the wings is greater , than the air pressure the wings . I . You carefully drop a stone into a beaker full of The plane is presumed ' water . The stone sinks to the bottom and water . You observe that a chunk of tar sinks in spill out . What can you say about the weight puddles of rainwater but Am the ocean . of the displaced water ?

An experiment to explain the behavior of the A It is greater than the weight of the stone . lit I It is equal In the weight of the stone . A the difference between atmospheric it is less than the weight of the stone . 55 ! 35 ' It is equal In the weight of the water still he 4911551555 Of 155 3311 ! in the beaker . ind the height from which the chunk of tar is dropped . the depth of each type of water . Use the photos below to answer Question . A helium balloon rises because the helium A is hotter than the air . is colder than the surrounding air . is less dense than the surrounding air . is more dense than the surrounding air . Explain why objects experience a buoyant when immersed in a . you the value of the buoyant ?

How can , You , pend , four knowing the density of an object and a different unknown liquids . labeled A . and ' Vi 04 ' Sink The at different levels in 16 ?

in the four liquids . Which liquid is the most dense ?

A liquid Liquid Liquid our Motion and Energy You can describe the motion of an object by its position . speed , direction . and acceleration . is an object in motion ?

How do you calculate speed ?

How do you calculate acceleration ?

What affects an object kinetic energy and potential energy ! Chapter 10 . An unbalanced force will cause a change in an objects velocity How do balanced and unbalanced forces affect velocity ?

do objects accelerate during free fall ?

is Newton second law of motion ?

What is Newton third law of motion ?

keeps a satellite in Chapter 11 Forces in Fluids CREE If an object is less dense than I . it will float In the fluid . If an is more dense than a . it will sink In the . How do fluids exert pressure ?

What is the effect of the buoyant force ! does Pascal principle say about change in fluid pressure ?

How is fluid pressure related to the motion of a fluid ?

El El Welcome to the Summer Triathlon . Do you have what it takes to compete in all three athletic events ?

Today triathlon will begin with a swim . We set up buoys floating in the water so you can follow the path of the race properly . Do swim too far away from these floating markers , or go off course and have to get back on Next you will cycle 20 . When you get to the finish line , remember to brake as quickly as possible so you can start the last leg of the event . Finally , you will have to run along the edge of the lake . The view is beautiful , but do forget to keep your eye on the prize . You have to turn around at the halfway mark and change direction because the race finishes at the same bridge where it begins . Remember to pace And at the end , we have a special surprise for you . All athletes who complete the triathlon win a medal ! It took you half an hour to run the final of the triathlon . Using that information . what can you find ?

Chapter ) average speed I ) instantaneous speed acceleration direction . At the end of the bicycle race what kind of friction do you rely on when you use your hand brakes to come to a stop ?

Chapter 10 ) static friction sliding friction rolling friction . fluid friction . Which of the following is a possible density for the buoys in the . Summary Write a paragraph that describes ( Chapter 11 ) the different forces you experienced while running in the triathlon . Did these forces . 90 900 cause changes in your motion ?

Explain .

Interdisciplinary Exploration . From Vines to Steel Have you ever balanced on a branch or log to cross a brook ?

jumped from rock to rock in a ?

swung on a vine or rope over a river ?

you have used same ways . that early vim used In ! A ( ow , nun vines . mud stones Ill River in northern Pakistan . lim bridges . Bridges of over . llI ( Ill , ul , bridges have also served as forts for defense . scents . and for and ( Silt ) of , love . and . span cities . and and encouraging mule ind . But ' not always an elaborate as they are today . The earliest mad materials and plentiful . in deep farms . people used Roman Fame Angelo is in Rome . mad small . tropical regions where vegetation ins thick , people wove vines and . then hung them In . wall over rivers and gorges , A , No mailer what ur . I . bridges who . China . and Rome all designed strong . graceful bridges In and . 4500

Science The Balance of Forces . keeps bridge from falling down ?

How does it support its own weight and the weight of people and on it ?

Builders found the answers by considering the forces that act on bridge . The weight of the bridge and the on it are called the land . When a heavy ( a beam bridge . the weight the load forces the beam to curve downward . This creates tension forces that stretch the beam . At the same time . the load also creates forces at the top oi the beam . Since the bridge does collapse under the load . there be upward forces to balance downward forces . In simple beam bridges . builder anchor the beam to the ground or to end called al . To Cross longer spans or distances , they construct piers under the middle spun . Piers and are structures that act an upward forces . ot bridge , the arch bridge , supports its load . A heavy load on stone arch bridge or the together . creating compression throughout the . Weight on the arch bridge pushes down In the ends of the arch . The side wall and as reaction . ETi i at . Compression force Compression force . Tension ( ES om learn Bridge A beam bridge spans the Rhone River In France ( top ) engineers discovered that bridges made could span wider ( than simple beam bridges . Arch bridges are also stronger and more durable . Although the were not the lirst to build arch bridges . they perfected the form in their massive . elegant structures . Roman arch bridges were built without . ur The arch held together because the were skillfully shaped to work in compression . Alter nearly , I ) It years , some of these Roman arch bridges are still standing . Compression .

The Structure of Modern Bridges By the 121005 in the mind Mud bridges the sauna begun Iu usc ( am iron and woud . do . A ' ISM ) mung ul . no bridge I In ( In strong and . ent new bridges . are stretched , mu nut , ul giant ( uf Thu of the . as well . lound ( ha ! they could vi , hy build grr , Th weight or the bridge and mu . load on it an to pull apart or the . pulling ( bridge ' The ' a an as . I . inn the . can lung dis ! Inc 02 ( is walking an . The Su forum in a su bridge ul people mun . pushes down on the ropes . stretching them ( form I Suspension Bridge Th sun mes the Golden Gate ( 451

the Bridge In New York ( 18143 , it th ) bridge in world . The ( Sale Bridge in Sun . which opened in 1937 , was gran Ital . Recently . eng , developed a new design . It ) to 21 ' arc with towers and cables . But two arc . on cable stayed bridge mach ' so the ' bun wright of the bridge and load un it , In contrast . the LAME on and anchor at . the tower ' Mat the loud Bridge The Sunshine Skyway Budge spans a section at Tampa any Florida The ( attached to the center ot the roadway , enable travelers to have a clear mew Science Activity Work in groups to make a suspension bridge . using two chairs , a wooden plank , rope . and some books . Place two chairs and stretch tapes over the backs of the ( Hold the ropes at both ends pieces of rope to the longer ropes . the plank through the loops . th a partner , hold the ropes tightly at each end . Load books on top of the plank to see how much it will hold , Why is it important to anchor the ropes tightly at each end ?

Brooklyn Bridge This ?

and Manhattan ( above ) It tuck 14 years tor to the bridge ( lelt ) Against All Odds When John was hired in 1868 to build the Brooklyn . it skilled bridge . He had been working un fur the bridge since . But began in 1869 , died in a construction accident . Fortunately he had worked out his design In the bi detail . His son . who was skilled engineer . nut his father plan . The dragged on tur wear and cost nearly 30 ' Roebling so disabled that he forced to . ruin his home . Using a ( followed every detail . His wile , Emily . enough engineering to deliver and his to the workers . mun As the giant ' A were up , the steel wire hack and forth the In Ihr cables . The next was to twist the wires together . But the hanging so high on the bridge and refused tu . Frank . the chief mechanic . the river on a small chair dangling A wheel that ran ) an overhead line . completed his to the war of the crowd . Somewhat , the builders returned in work . But it took ' more to string the cables . Thu was um the in the end . the Bridge project . only of the and of the . the model fur bridges . Social Studies Activity How do you think the Bridge changed the lives at New Yorkers ?

in groups . research the history of another famous bridge Present your findings to your along with drawings and photos . Find out I when and why the bridge was built what type of bridge it is what effects the bridge has on trade , travel . and population how affected the bridge building about events connected to the bridge

' 15 , Brooklyn Bridge was yesterday . The pleasant weather visitors by the from all AIr were in . which it mu almost impossible to . and those who had tu attend the had hard work lu reach the . top and window was tilled . and an party tall telegraph pole . It required the of the police to keep clear the space . Altar at the were completed the was and the march um taken up to Roebling residence . From the hack study ( in the second floor ! his ( Sol . had watched his the procession as it proceeded along from the New side until the was reached . received at her ' side and her of the ut the bridge . Brooklyn Bridge historic painting shows fireworks at the opening of the bridge in 1383 . THE lU ?

Lli ' i ' Language Arts TWO GREAT CITIES UNITED For blocks and blocks on either oi the bridge there was scarcely a font at mum in . Many crossed and ed the river on the terry ) and in that watched the display . every along the river was converted into a grand stand . The ceremonies of the ripening great , in at eight , when the tirst ' was sent the center of the great . and at nine , when A flight of 500 rockers illuminated the sin . The uni lila ' til light , and the yachts and smaller blue were burning and illuminating dark waters around them . the Language Arts Activity A reporter goal is to inform and entertain the reader Using a ( opening line draws interest . Then the reader wants to know the , what . where . when , why , and how ( and ) You are a reporter Write about the opening of a bridge in your area . It could be a highway overpass or a bridge over water , a valley , at railroad I some at the and Add interesting details and . 455

Bridge Geometry increased in . Using basic structures . engineers popular . Designed with thin In un truss and diagonal supports to add , designs . The ( the is to trim were ) the stress train loads and structures . uf the early bridges constant . As in all bridge structures . could the trains that over each piece has In Ul and them . List iron steel trusses mun . lengths . angles . and wood trusses . palms of interstitial ! and . Geometric and Figures Engineers use various geometric figures In drawing budge plans . Figures that have right angles are squares . rectangles . and right triangles . that have acute angles and obtuse can be triangles and parallelogram . Forces Acting on Geometric Shapes A bask triangle in a A square or rectangle truss bridge is strong is not as strong as a because shape triangle . can not be . A triangle In I truss A square or rectangle bridge can support a can collapse into a heavy load with the parallelogram under a shape relatively small weight . heavy load .

Math Activity The building engineer has asked you to draw up exact plans for a new truss Review the captions and labels on the which lines are parallel ?

Whi ( lines intersect ?

What kind of is formed by ?

Ti A Truss bridge over Rio Grande Gorge In New bridge . How well will you do as an assistant ?

previous page . Then answer these questions . What kind of figure is fanned by ?

What kind of angle is or right ?

What kind of angle is ?

What kind of triangle is ?

What makes it this kind of triangle ?

why is a triangle stronger than a square ?

It Together work in small groups to build a model of a bridge out at a box of spaghetti and a roll of masking tape . Meet as a group to choose the type of bridge you will build . Each bridge should be strong enough to hold a . You can build a beam bridge a truss bridge an arch bridge a suspension bridge ( This one is challenging . After drawing a sketch of the bridge design . assign jobs for each team member . Then decide how long the bridge span will be measure and cut the materials build the roadway for beam , truss , and suspension bridges build the arch first in an bridge when your bridge is complete , display it in the ( lest the strength of each bridge by placing a brick on the roadway . Discuss the in bridge structures . Determine which bridge design is the strongest .