Forces and motion investigations

36 Pages·2018·3.743 MB·English

by  Kenney, Karen Latchana

FORCES
MOTION
AND

I N V E S T I G A T I O N S
KAREN LATCHANA KENNEY
THIS PAGE
INTENTIONALLY
LEFT BLANK
FORCES
MOTION
AND

I N V E S T I G A T I O N S
KAREN LATCHANA KENNEY
Lerner Publications Minneapolis
To our future scientists and their unknown discoveries 
Content consultant: Kevin Finerghty, adjunct professor of Geology
at State University of New York, Oswego; Earth science teacher at
Pulaski Academy and Central Schools, Pulaski, New York
Copyright © 2018 by Lerner Publishing Group, Inc.
All rights reserved. International copyright secured. No part of this
book may be reproduced, stored in a retrieval system, or transmitted
in any form or by any means—electronic, mechanical, photocopying,
recording, or otherwise—without the prior written permission
of Lerner Publishing Group, Inc., except for the inclusion of brief
quotations in an acknowledged review.
Lerner Publications Company
A division of Lerner Publishing Group, Inc.
241 First Avenue North
Minneapolis, MN 55401 USA
For reading levels and more information, look up this title at
www.lernerbooks.com.
Main body text set in Aptifer Slab Regular 11.5/18.
Typeface provided by Linotype AG.
Library of Congress Cataloging-in-Publication Data
Names: Kenney, Karen Latchana.
Title: Forces and motion investigations / by Karen Latchana Kenney.
Description: Minneapolis : Lerner Publications, [2018] | Series: Key
questions in physical science | Audience: Age 8–12. | Audience: Grade 4
to 6. | Includes bibliographical references and index.
Identifiers: LCCN 2016045747 (print) | LCCN 2016046144 (ebook) |
ISBN 9781512440089 (lb : alk. paper) | ISBN 9781512449570 (eb pdf)
Subjects: LCSH: Gravity—Juvenile literature.
Classification: LCC QC178 .K43 2018 (print) | LCC QC178 (ebook) | DDC
531/.11—dc23
LC record available at https://lccn.loc.gov/2016045747
Manufactured in the United States of America
1-42270-26127-3/10/2017
CONTENTS
INTRODUCTION
ULTIMATE BOUNCE 4
CHAPTER 1
WHERE DOES MOVEMENT
COME FROM? 6
CHAPTER 2
WHAT KEEPS THE MOON FROM
FLOATING INTO SPACE? 12
CHAPTER 3
WHAT MAKES THINGS MOVE? 18
CHAPTER 4
HOW DOES A ROCKET
ESCAPE GRAVITY? 25
TRY IT! 28
GLOSSARY 30
FURTHER INFORMATION 31
INDEX 32
INTRODUCTION
ULTIMATE BOUNCE
Your team steps onto the court.
It has wall-to-wall trampolines,
and you’re about to play the ultimate
game of dodgeball. Grab a ball and get
jumping! You jump onto the trampoline
and push the stretchy fabric down. It pushes
back, launching you high into the air as you
throw your ball at the other team.
Forces are at the
heart of the science
behind trampolines.
What’s happening with each bounce? Forces and motion
are at work. Your first jump is the force that gets your
motion going, and the force of the stretchy trampoline keeps
you bouncing.
Have you ever wondered about a trampoline’s bounce? Or
why the moon keeps circling Earth? Curious scientists also
ask these kinds of questions. They study the world and think
about how it works. They test their ideas and come up with
answers based on their evidence.
Everything on Earth and beyond feels the effects of forces.
5
CHAPTER 1
WHERE DOES MOVEMENT
COME FROM?
How do you send a
basketball flying into a
hoop? You need to use force.
The many different kinds of
forces are all just a push or
a pull. Forces can get things
moving or make them
stop. They’re the reason
we have motion.
EARLY
THOUGHTS
ON FORCES
AND MOTION
Forces have fascinated scientists It takes forces to make
a basket, but scientists
for centuries. Ancient Greek
didn’t always understand
philosopher Aristotle studied forces. what forces were or how
they worked.
7
He hypothesized that an object’s motion was caused by its
need to find more objects like it. Aristotle wondered whether
rocks and soil were attracted to each other, since they were
both made of earth. He tested his theory and observed it
being confirmed in nature. Modern scientists know that
rocks fall because of gravity. But Aristotle’s hypotheses gave
later scientists lots of ideas to test. Aristotle’s early questions
started to form our understanding of forces and motion.
DIFFERENT FORCES
Although he was wrong about the cause, Aristotle did
understand that motion begins with a push or a pull.
Aristotle thought
objects on Earth
were made of a
combination of four
elements: water,
earth, air, and fire. He
saw rocks fall to the
ground and thought
the motion was
caused by the rock’s
need to find more
earth elements.
8
That push or pull is caused by different kinds of forces.
Contact forces happen when two things touch. The force
that helps you jump high on a trampoline is a contact force.
Friction is the contact force that resists motion
between things that are in contact. It helps us grip the
ground when we walk, but it also slows things down.
Italian artist and scientist Leonardo da Vinci
wondered why heavier objects are harder to push
or pull and move more slowly than lighter objects.
When you jump on a trampoline, you push down on the trampoline and it pushes
back at you. The springs stretch, and elastic force launches you into the air.