Exploring forces and motion

pull things toward them and push things away.. Vocabulary attract force friction gravity motion repel simple machine work Picture Credits Every effort has been made to secure permission

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Scott Foresman Science 2.10

Nonfi ction Put Things in Order • Captions

• Glossary

Forces and Motion

ISBN 0-328-13797-9

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Scott Foresman Science 2.10

Nonfi ction Put Things in Order • Captions

• Glossary

Forces and Motion

ISBN 0-328-13797-9

ì<(sk$m)=bdhjhi< +^-Ä-U-Ä-U

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1 When do you need to use more

force to move objects?

2 What are some simple machines,

and what do they do?

pull things toward them and push things away Write to explain how they do this Use words from the book as you write

4 Put Things in Order Tell what

happens in order when you throw

a ball up in the air Use the words

force and gravity

What did you learn?

Vocabulary

attract

force

friction

gravity

motion

repel

simple machine

work

Picture Credits

Every effort has been made to secure permission and provide appropriate credit for photographic material

The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions.

Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd).

5 Getty Images; 8 (TL) ©AFP/Getty Images, (TR) ©Chapman/NewSport/Corbis; 12 (BR) Paul Hobson/Alamy Images.

ISBN: 0-328-13797-9

This publication is protected by Copyright, and permission should be obtained from the publisher prior to any

prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic,

mechanical, photocopying, recording, or likewise For information regarding permission(s), write to

Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025.

3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 05

by Sasha Griffi n

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How Objects Move

Objects move in many ways We call the act

of moving motion.

You can push a crayon across a piece of paper

in a straight line or a zigzag motion

You can move a tennis ball up and down

A Ferris wheel moves around in a circle

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Force

You use force to throw a ball and

to make it change direction.

We use force to move things Force is

a push or pull that makes something move

Objects move in the direction they are pushed or pulled When the direction of the force is changed, an object moves in that different direction

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You can make an object move faster by using

more force The merry-go-round will move faster

if the boy pushes harder It takes more force to

move heavy objects than light ones

Would the boy need to use more

force to push the merry-go-round

when it is empty or when it is

full of kids?

5

Gravity

When you throw something into the air,

gravity will pull it down Gravity is a force

that pulls things toward the center of Earth

What do you think will happen when these children jump up? Gravity will pull them back down

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Work

When a force moves an object, we call

that work No work is done when an object

does not move When you pick up a pencil,

you are using force and doing work

7

When you push a shopping cart, you are doing work It takes more work to push a heavy cart than to pick

up a pencil That is because you use more force to move the cart

It takes a lot of work

to move a heavy shopping cart.

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Changing the Way

Things Move

You use more force the farther you move an

object An object will not move very far if you

push it gently If you push it hard, it will go far

You are doing work when you push a light

object across the fl oor You would do more work

if you pushed a heavy object across the fl oor

A gentle kick uses little force A hard kick uses great force.

9

Friction

Friction is a force It slows down or stops

moving objects You can skate faster on the sidewalk than on the beach That is because friction between the wheels and the sand makes the skates slow down

When you rub your hands together, they warm up The friction between your hands makes heat

Roller-skating

on the sidewalk

is easier.

Roller-skating

on sand is hard!

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Simple Machines

Machines are tools

They help us do work

A simple machine has

few or no moving parts

A wedge is a simple machine that pushes things apart A lever is used to move things Screws are simple machines that hold things together

A screwdriver can

be used as a lever.

A screw is a simple machine.

This axe is

a wedge.

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A wheel and axle make a simple machine

When you put force on one wheel, the axle turns the other wheel too

An inclined plane is higher at one end

This makes it easier to move things

A pulley is made up of a wheel and a rope

It can lift, lower, or move an object sideways

This is

a pulley.

This wooden ramp

is an inclined plane.

wheel

A bicycle has two wheels and two axles.

rope

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Some animals have body parts that work

like simple machines

A woodpecker pecks holes in tree trunks

Its beak is like a wedge

Moles have front feet that they use like

levers They move dirt as they dig

Animal Body Parts

A woodpecker uses its beak like a wedge.

beak

12

A mole uses its front feet like levers.

13

Magnets

Magnets are used in many ways Magnets

attract some types of metal That means they

pull some metal objects toward themselves

Magnets can push away, or repel, other magnets.

A magnet’s force can move some objects without touching them

Magnets stick to a refrigerator because it is made of metal.

magnet

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A magnet has two ends, or poles We call one

end the north pole and the other the south pole

A magnet’s strongest push or pull is at the poles

Try putting two poles that are the same

together The magnets will repel each other

If you put the opposite poles together, the magnets

will attract each other

14

S S

N N

15

What Magnets Attract

Magnets attract objects made

of iron or steel They do not attract all kinds of metal A magnet will attract steel paper clips It will not attract a gold ring Gold is

a different kind of metal

Magnets do not attract things made of wood, plastic, or paper

Do you think a magnet will attract

a crayon?

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Glossary

something move

moving objects

toward Earth’s center

simple machine a tool that has few or no

moving parts

moves an object