Science Friction

FOCUS Book

Beyond the Book

A pinwheel spins in the breeze. Design and build a simple pinwheel with paper blades that will spin fast. To make it spin well, you will need to reduce the friction between the pinwheel and its base.

Design your pinwheel with parts or materials that create very little friction. What are some other ways your design can reduce friction and help the blades spin faster? Test your pinwheel in front of a fan. Keep the fan at a steady speed and keep your pinwheel at the same distance for every test.

Talk to other students about their pinwheels. Observe which design spins fastest. What changes can you make to improve your design?

Friction with the air is called wind resistance. Go online to explore how athletes in different sports reduce wind resistance.

Science Friction

Science Friction © Learning A–Z Written by Katherine Follett

All rights reserved.

www.sciencea-z.com

Photo Credits: Front cover, page 9 (right): courtesy of NASA; page 2: © STOCK4B GmbH/Alamy; page 3: © Jacek Chabraszewski/ 123RF; page 4 (left, top to bottom): (1) © khorzhevska/iStock/Thinkstock; (2) © Grassetto/iStock/Thinkstock; (3) © Joggie Botma/iStock/Thinkstock; (4) © ViktorCap/iStock/Thinkstock; page 4 (right, top to bottom): (1) © 1971yes/iStock/Thinkstock; (2) © Grassetto/iStock/Thinkstock; (3) © marcutti/iStock/Thinkstock; (4) © Aksonov/iStock/Thinkstock; page 5 (top): © Milan Vasicek/Hemera/Thinkstock; page 5 (bottom): © veryan dale/Alamy; page 6 (top): © dmitrydesign/iStock/Thinkstock; page 6 (bottom): © Gregory21/Dreamstime.com; page 7: © Lawrence Weslowski Jr/Dreamstime.com; page 8 (top): © iStock/dandanian; page 8 (bottom): courtesy of NASA/JPL/University of Arizona; page 9 (left): © Alan Dyer, Inc/Visuals Unlimited/Corbis

2

It’s a cold day, and you forgot your mittens. You rub your chilly hands together. Suddenly they feel warmer. Where did that warmth come from?

The warmth in your hands came from heat energy generated by friction. Friction is a force. It acts between objects that rub against each other. Friction also causes moving things to slow down. It changes the energy of a moving object from motion into heat.

Warm Up with Friction

How is friction related to heat energy?

FOCUS Question

Friction can help you warm your hands on a cold day.

Cause and Effect

Science Friction

Reading Levels

Learning A–Z R

Lexile 620L

Correlations

Fountas and Pinnell* N

*Correlated independent reading level

Heat Energy • Science Friction 3 4

You use friction every day. When you walk, run, jump, and stop, your feet touch the ground and create friction. If you wear skates with wheels, you have less friction with the ground. Zoom!

It’s harder to walk through water than through air. If you run through water, it only gets harder. Water has more particles in the same amount of space than air does. More particles mean more friction.

As speed increases, so does friction. Mass, or the amount of matter, creates more friction. It is easier to push an empty box than a full one. The size of a surface can also affect friction. It is easier to push a skinny box than a wide box. A rough surface causes more friction. It’s easier to push a box across a smooth floor than across a carpet.

What Is Friction? Factors of Friction

Friction happens between all kinds of matter—solids, liquids, and gases. Matter makes up everything around you. All matter is made of tiny particles. When things rub together, the edges of the particles catch. This is friction. Friction happens whenever matter touches.

As particles catch and pull apart again, they move back and forth. The movement of particles is heat.

Less friction

more friction

small mass

large mass

small surface

wide surface

low speed

high speed

smooth surface

rough surface

How will friction be important in this race?


Friction changes motion into heat. Lots of friction makes lots of heat. If wheels are moving fast enough, the tires will start to smoke and burn (see cover). At times, you can get enough heat to start a fire!

Matches use friction to create a flame. The head of a match catches fire at a fairly low temperature. The match lights when it is rubbed quickly across a rough surface. This friction gives off heat, so the match catches fire.

Some people can light a fire by rubbing two sticks together. Wood must be at a much higher temperature than a match head before it will catch fire. It takes a lot of skill—and a lot of patience—to light a fire by using friction.

Machines can create lots of friction and, as a result, lots of heat. When machines get too hot, their parts can short-circuit, melt, or even catch fire.

Many machines have ways to prevent friction. Some have tiny parts called ball bearings between their moving parts. The bearings roll past each other. Rolling causes a lot less friction than sliding. Other machines use lubricants, or slippery materials, to prevent friction. Oil and grease are lubricants.

Some machines need friction to do their jobs. A saw can’t cut wood without rubbing against it, but the motion heats the blade. When machines get too hot, people cool them using water, fans, or air conditioners.

Machinery and FrictionFire from Friction

A match head catches fire when friction heats it up.

Spinning a stick against another stick causes friction. Eventually, a flame may start.

Machines that spin, such as drills and wheels, have bearings inside.

ball bearings

Water cools this drill bit as it cuts through metal.

Never light matches without the help of an adult.


Cars are complex machines with many moving parts. Friction in a car is sometimes useful. Friction between the tires and the road allows the car to move.

Brakes also use friction. Brakes slow a car by rubbing against the wheels. Car brakes can get very hot, so they are made of special materials that will not crack or melt in the extreme heat.

Internal FrictionFriction in CarsYou have learned that friction happens when two objects touch each other. It also happens inside an object when it bends, stretches, or changes shape. This is called internal friction. This type of friction also makes heat.

When you bend an object, the object’s particles catch on each other. This causes friction. Try bending a metal paper clip back and forth several times. Briefly touch the spot where you bent the clip. It will feel warm!

Race cars use high-tech materials in their tires, brakes, and engines to reduce friction caused by high speeds.

A car’s engine has many fast-moving metal parts that create a lot of friction. Oil helps lubricate these parts and keeps them running smoothly.

Some of the paper clip’s mechanical energy is converted to thermal energy.

The moon Io (EYE-oh) orbits the planet Jupiter. Jupiter’s gravity is so strong that it stretches and squishes Io. Friction inside Io generates heat. It makes so much heat that Io’s interior is melted! The heat even causes volcanic eruptions.

For each 10 km per hour that a car slows down, the brakes heat up by 3°C. A car is traveling 40 km per hour. The brakes start out at 25°C. How hot will they be after the car comes to a complete stop?


You may not notice it, but air causes friction every time you move. At very high speeds, friction with the air creates a lot of heat.

A meteoroid is a bit of rock that falls toward Earth from space. As a meteoroid hits Earth’s atmosphere, friction with the air starts to heat it up. The heat is so great that most meteoroids burn up completely.

Spacecraft must withstand the heat caused by friction when they exit and reenter Earth’s atmosphere. Spacecraft have special heat shields that protect astronauts from the heat of friction. Once a spacecraft is in space, there is no friction. Why? There is almost no matter to rub against in space!

Write your answers on separate paper. Use details from the text as evidence.

1 Where does the energy come from to create friction, and what does friction give off?

2 Based on what you learned on page 5, which method would you choose if you were cold and needed to start a fire quickly? Why?

3 Using the information you learned in the section about friction and machines, how would you reduce the friction generated by a bicycle when you pedal it?

4 Choose one example from the book to demonstrate how friction is helpful when driving a car.

5 Why does a spaceship need a special shield when it reenters Earth’s atmosphere?

How is friction related to heat energy? Using information from the book, describe an example from your own life of when heat from friction can be useful and an example of when it can be harmful.

FOCUS Question

Friction in the Atmosphere

When meteoroids burn up, they make streaks of light, better known as “shooting stars.”

The outside of the space shuttle Endeavour protected the astronauts from extreme heat.

heat shield

Use the information you just learned to make a submersible that will sink and then rise in a half-meter-deep tub of water. You can use different small containers as submersibles, changing them to help them float or sink. Add weights, such as paperclips or coins, for ballast. You can use vinegar and either baking soda or antacid tablets to make gases inside the containers. Gases will help make your submersible rise.

Try different methods. How does adding and removing ballast affect your sub? What happens when you use more weight or more gas? Sketch your sub designs. Describe what happens as you change the variables.

Use the Internet to investigate the future of space travel. What might rockets look like in the future? What sources of power might they use?

Beyond the Book

FOCUS Book

Spaceship Motions

and Deep, Deep

Oceans

Spaceship Motions

and Deep, Deep

Oceans

Think about traveling to the bottom of an ocean. It is dark and cold. The water above you is very heavy. The pressure is more than 1,000 times greater than on land.

Now think about traveling into space. It takes a lot of fuel to escape the pull of Earth’s gravity. Then, once you are there, you have to deal with feeling weightless.

We have designed machines that can go to these extreme places. We have explored our solar system and the deep ocean. Which machines do we use? What makes them work?

Extreme Travelers

How do machines help people explore outer space and the deepest oceans?

Structure and Function

FOCUS Question

The air pressure needed to inflate a balloon is small compared to water pressure in the deep ocean.

Astronauts must deal with feeling weightless.

Spaceship Motions and Deep, Deep Oceans © Learning A–Z

All rights reserved.

www.sciencea-z.com

Photo Credits: Front cover (top): © Photos 12/Alamy; front cover (bottom): © Andrea Danti/123RF; page 2 (top): © Dimitri Surkov/123RF; pages 2 (bottom), 4 (left), 5 (center): courtesy of NASA; page 3: © Vasily Smirnov/123RF; page 4 (right): © Eniko Balogh/Dreamstime.com; pages 5 (top), 9 (center): © Bettmann/Corbis; page 5 (bottom): © JG Photography/Alamy; page 6 (left): © iStock/GeoffBlack; page 6 (right): © Alexander Pladdet/Dreamstime.com; page 9 (top): © charistooane-images/Alamy; page 9 (bottom): © Mike Dimestico/NMCS/EPA/Landov

Illustration Credits:page 7: © Q2A Media Inc.; page 8: Q2A Media Inc (source: How Stuff Works)

2

Reading Levels

Learning A–Z R

Lexile 650L

Correlations

Fountas and Pinnell* N

*Correlated independent reading level

Rockets and ShuttlesFighting GravityBlow up a balloon and let it go. What happens? It flies! The balloon pushes away air. The air pushes the balloon in the opposite direction. This is similar to how a rocket engine works.

When you blow up and release a balloon, it goes only a short distance. Rockets go all the way to outer space! This takes a lot of fuel. When rocket fuel burns, some of its energy changes into heat, light, and sound. The rest changes into motion.

Gases rush from the bottom of the rocket, toward the ground. The rocket flies in the opposite direction, up into the sky. This force is called thrust. The upward thrust must be stronger than the downward pull of gravity for the rocket to fly.

Between 1969 and 1972, people went to the Moon! They flew in Saturn rockets. These rockets had more than one engine. The bottom engine was the biggest and produced the most thrust. When this engine blasted off, it pushed the rocket up very high and then dropped away when it ran out of fuel. A second engine then fired up to take the rocket the rest of the way to the Moon.

Later, engineers designed spaceships that were shaped more like airplanes. They could be used more than once. These were called space shuttles.thrust

gravity

Saturn rocket

space shuttle

Machines • Spaceship Motions and Deep, Deep Oceans 3 4

Over the years, people have made rockets that go higher and higher.

Submarines have the opposite problem of rockets. They need to go down instead of up! While rockets fight gravity, submarines must work against buoyancy (BOY-un-see). Buoyancy is the upward push of a liquid or gas. It is what makes things float in water—or on air.

To submerge, or go underwater, submarines must overcome buoyancy. They do this by becoming denser. Density is the amount of material in a certain space. Think of a piece of cork and a solid rock that are the same size. The rock has more material in it. The rock is denser than the cork. A cork floats in water, while most rocks sink.

Fighting Buoyancy

V-2 ROCKET The V-2 rocket was the first rocket to go into space. It was only 14 meters (45 ft.) tall, but it had a lot of thrust.

SATURN V ROCKETS Saturn V rockets were the tallest and heaviest rockets ever built. They were 110 meters (363 ft.) tall.

SPACE SHUTTLES Only six space shuttles were made. They were used to transport humans and tools into space and back. Scientists conducted experiments on the space shuttles.

Which is denser: this rubber ball or the bowling ball? Why? How could you test your answer?

Space shuttles orbited Earth quickly. The astronauts on board saw a sunrise or sunset every 45 minutes!


How is the density of a submarine changed? The submarine crew uses seawater and ballast tanks.

The crew fills ballast tanks with seawater. This makes the submarine denser so that it can dive. Some can go 274 meters (900 ft.) below the surface of the ocean.

The submarine rises when it becomes less dense. Water is forced out of the tanks. Air is put back into the tanks.

Submarines are used for many jobs. That is why they can be many sizes. A small submarine is called a submersible.

Submersibles are used to explore the ocean. Most of them hold three people and use batteries for power. They can go to the deepest place on Earth—the Mariana Trench. This place is over 11,000 meters (36,089 ft.) below the ocean surface!

Big submarines can travel long distances in the ocean. They can hold 140 people. Submarines have their own engines and can stay underwater for 90 days! They cannot dive as deep as submersibles, however.

Deep DiversHOW A SUBMARINE

DIVES AND RISES

When the ballast tanks fill with water, the submarine dives. When the ballast tanks fill with air, the submarine rises. Vents and openings control what goes in and out of the tanks.

air tank

vents

opening

ballast tank

2.1 m

0 m

290 m

4,000 m

6,000 m

9,500 m

11,000 m

Jason (submersible)

Los Angeles

Turtle

Trieste

Mariana Trench

Some submarines and submersibles can go deeper than others.

Dep

th belo

w sea level

source: How Stuff Works

Ballast is any heavy material that is used to make a ship denser.


Write your answers on separate paper. Use details from the text as evidence.

1 Which force do rockets have to overcome, and how do they do so?

2 What is an advantage of having a two-engine rocket like the Saturn rockets had?

3 Which force do submarines have to overcome, and how do they do so?

4 Look at the diagram on page 7. Describe how a submarine dives.

5 Are rockets affected by buoyancy? Explain your answer. If so, how does this force change how rockets move?

How do machines help people explore outer space and the deepest oceans? Describe a challenge of space travel and a challenge of exploring the deep ocean. Explain how people have overcome these challenges.

FOCUS Question

LOS ANGELES CLASS SUBMARINE Submarines in use today are much bigger than older ones. The Los Angeles class submarine is 110 meters (362 ft.) long—longer than the Statue of Liberty is tall!

THE TRIESTE The Trieste was the first submersible with people aboard to visit the deepest spot on Earth—the Mariana Trench. The two-person crew explored the ocean floor for only 20 minutes.

Submarine and submersible designs have been improved over time.

THE TURTLE One of the first submersibles was called the Turtle. It used hand-powered paddles to move and long hoses to get air from the surface.


1© Learning A–Z All rights reserved. www.sciencea-z.com

Name Date

Balanced and Unbalanced Forces

Lesson 1

Part 1: Evaluate the ForcesVanessa and Leon are playing soccer in the park. They want to find out how the ball will move when they kick it in different ways. Read the forces they applied to the ball. Then circle the correct distance and direction to show how the ball moved in each example. Circle as many boxes as you need to.

1. Leon lightly kicked the right side of the ball with the inside of his right foot.

Distance Direction

short longdid not move

forward backward left rightdid not move

2. Vanessa kicked the ball hard from directly behind it.

Distance Direction



3. Vanessa and Leon each put one foot on opposites sides of the ball and lightly pushed on it with equal force.

Distance Direction



4. Leon kicked the ball hard from directly behind it, but then a strong gust of wind hit the left side of the ball.

Distance Direction



Storyline Assessment


Name Date


Lesson 1

Part 2: Plan an InvestigationSuppose you would like to investigate how balanced and unbalanced forces affect the motion of a flying disc. Draw a line to match each question with the step you could use to conduct a good experiment. Read all the steps before making your choices.

1. What do you want to find out?

I will write my observations and measurements in a data table.

2. How will you perform tests to find out?

I want to know how applying different forces to a flying disc will affect its motion.

3. What will you measure?

I will look for patterns in the data table. I will compare how the disc moved when different forces were applied.

4. How will you record the results?

I will throw the disc with different strengths. I will run each test three times. I will also observe how the wind affects the disc.

5. How will you use the results to answer your question?

I will find the distance the disc flies from the starting point to where it lands, and I will observe the direction the disc flies.



Name Date


Lesson 1

Part 3: Carry Out an InvestigationPlace an unsharpened pencil on your desk with the long side facing you. Try each of the tests listed below. In the data table, describe the direction the pencil moved and how far it moved. Then answer the questions.

Test Direction and Distance

A. Use one finger to very lightly push the pencil.

The pencil moved _________________________

and rolled a ________________________ distance.

B. Use one finger to push the pencil a bit harder.

The pencil moved _________________________

and rolled a ________________________ distance.

C. Use two fingers to push at the same time on both ends of the pencil.

The pencil _________________________.

D. Use one finger to lightly push the eraser.

The pencil moved _________________________

and slid a ________________________ distance.

1. In which test or tests were the forces balanced? Test A Test B Test C Test D

How can you tell?

2. In which test or tests were the forces unbalanced? Test A Test B Test C Test D

How can you tell?

3. How did friction affect the motion of the pencil?


ANSWER KEY AND TEACHING TIPS


* Next Generation Science Standards is a registered trademark of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards was involved in the production of, and does not endorse, this product.

Distance Direction



Distance Direction



Distance Direction



Distance Direction




Lesson 1

Connections to the Next Generation Science Standards*Target Science and Engineering Practice: Planning and Carrying Out Investigations• Plan and conduct an investigation collaboratively to produce data to serve as the basis for evidence,

using fair tests in which variables are controlled and the number of trials considered.

Associated Performance Expectation: 3-PS2-1. Plan and conduct an investigation to provide evidence of the effects of balanced and unbalanced forces on the motion of an object.

All questions in this assessment relate to the Disciplinary Core Ideas DCI of this Performance Expectation. Look for the SEP and CCC symbols for questions that specifically address Science and Engineering Practices and Crosscutting Concepts.

SummaryStudents decide how a ball moves when balanced and unbalanced forces are applied, recognize the correct sequence of steps for an investigation that would allow one to carry out a fair test, and conduct a simple test to directly observe and evaluate how various forces applied to a pencil affect its motion.

Part 1: Evaluate the Forces1.

2.

3.

4.

In example 4, the ball starts off moving forward, away from Leon, but then the wind gust hits the left side of the ball and pushes it to right.

CCC


Storyline Assessment Balanced and Unbalanced Forces

Lesson 1

Part 2: Plan an Investigation

1. What do you want to find out?

I wil l write my observations and measurements in a data table.

2. How wil l you perform tests to find out?

I want to know how applying different forces to a flying disc wil l affect its motion.

3. What wil l you measure?

I wil l look for patterns in the data table. I wil l compare how the disc moved when different forces were applied.

4. How wil l you record the results?

I wil l throw the disc with different strengths. I wil l run each test three times. I wil l also observe how the wind affects the disc.

5. How wil l you use the results to answer your question?

I wil l find the distance the disc fl ies from the starting point to where it lands, and I wil l observe the direction the disc fl ies.

Part 3: Carry Out an InvestigationTest Direction and Distance

A . Use one finger to very lightly push the pencil .

The pencil moved forward (or away) and rolled a short distance.

B. Use one finger to push the pencil a bit harder.

The pencil moved forward (or away) and rolled a longer distance.

C. Use two fingers to push at the same time on both ends of the pencil .

The pencil did not move.

D. Use one finger to lightly push the eraser.

The pencil moved (left or right) and slid a short distance.

SEP

SEP


Storyline Assessment Balanced and Unbalanced Forces

Lesson 1

1. The forces were balanced in Test C. I can tell because the pencil did not move when I pushed on the eraser and the unsharpened end of the pencil at the same time with the same force.

2. The forces were unbalanced in Tests A, B, and D. I can tell because in all three tests, the pencil moved when a force was applied.

3. Friction is a force that was acting on the pencil in each test. It caused the moving pencil to slow down and then stop.

Teaching TipsIf students have trouble performing the tasks on this assessment, ask them to look back at the data table they created during Lesson 1. Explain that when the forces acting on an object are balanced, a stationary object will not move, and a moving object will keep moving in the same way. When the forces acting on an object are unbalanced, a stationary object will start moving and a moving object’s motion will change. Whether and how an object moves depend on the strength and direction of all the forces acting on it. This represents a cause-and-effect relationship in which the forces acting on an object can cause a change that affects the object’s motion. Also, review the steps involved in carrying out a fair test, including the importance of defining the purpose of the test and the variables to be tested, before carrying out the investigation.

ExtensionsFor students who complete their work early or are ready for an extra challenge, assign additional resources related to this topic found on the Grade 3 Forces and Interactions NGSS page on Science A–Z.

CCC

Photo credits: page 1: © iStock.com/FatCamera; page 2: © iStock.com/mixetto

https://www.sciencea-z.com/main/NextGenerationScienceStandards/from_ngss_resource_menu/true/ngss_topic_id/10

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Science Friction