Genre Comprehension Skill Text Features Science Content Nonfi ction Cause and Effect • Captions • Labels • Glossary Forces and Motion Scott Foresman Science 2.1 Standards Preview Standard Set 1. Physical Sciences 1. The motion of objects can be observed and measured. As a basis for understanding this concept: 1.a. Students know the position of an object can be described by locating it in relation to another object or to the background. 1.b. Students know an object’s motion can be described by recording the change in position of the object over time. 1.c. Students know the way to change how something is moving is by giving it a push or a pull. The size of the change is related to the strength, or the amount of force, of the push or pull. 1.d. Students know tools and machines are used to apply pushes and pulls (forces) to make things move. 1.e. Students know objects fall to the ground unless something holds them up. 1.f. Students know magnets can be used to make some objects move without being touched. ISBN 0-328-23495-8 ì<(sk$m)=cdejfa< +^-Ä-U-Ä-U 23495_CVR_FSD.indd Cover123495_CVR_FSD.indd Cover1 2/1/06 1:46:55 PM2/1/06 1:46:55 PM by Kristin Cashore Physical Sciences 23495_CVR_FSD.indd Cover223495_CVR_FSD.indd Cover2 2/1/06 1:47:01 PM2/1/06 1:47:01 PM Vocabulary attract force friction gravity motion repel 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. Unless otherwise acknowledged, all photographs are the copyright of Dorling Kindersley, a division of Pearson. Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd). 4 Getty Images; 13 Jerry Young/DK Images. ISBN: 0-328-23495-8 Copyright © Pearson Education, Inc. All Rights Reserved. Printed in the United States of America. 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. 1 2 3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 23495_CVR.indd Cover323495_CVR.indd Cover3 12/30/05 4:12:38 PM12/30/05 4:12:38 PM by Kristin Cashore 23495_001-020.indd 123495_001-020.indd 1 12/30/05 4:16:18 PM12/30/05 4:16:18 PM 2 Learning About Position Position is where an object is. How can you talk about position? You can use words such as behind and in front of to talk about position. Look at the picture of the man and the girl. The man is behind the counter. The girl is in front of the counter. The water is to the left of the fruit. The woman is behind the counter. 23495_001-020.indd 223495_001-020.indd 2 12/30/05 4:16:19 PM12/30/05 4:16:19 PM 3 You can also use words such as left and right to talk about position. Do you see the water on the counter? It is to the left of the fruit. How can you use left and right to talk about the fruit? 23495_001-020.indd 323495_001-020.indd 3 12/30/05 4:16:21 PM12/30/05 4:16:21 PM 4 How else can you talk about position? You can talk about position based on something that does not move. The background does not change. The cabinets and stove do not move. They are in the background of the picture. Things in the background can help you talk about position. 23495_001-020.indd 423495_001-020.indd 4 12/30/05 4:16:22 PM12/30/05 4:16:22 PM 5 We measure things to learn more about position. Look at the fl owers and lemons in the picture below. Their positions can be measured. The fl owers are 1 meter from the sink. The lemons are 11 centimeters from the fl owers. Use meters and centimeters to measure. 1 meter 11 centimeters 23495_001-020.indd 523495_001-020.indd 5 12/30/05 4:16:26 PM12/30/05 4:16:26 PM 6 Learning About Motion Motion is the act of moving. In what way do things move? Some things move back and forth. Some things move around and around. Some things move in a straight line. The boy in the picture moves back and forth on the swing. The top spins around and around. Your car moves in a straight line. The cars move in a straight line. The boy swings back and forth. The top spins around and around. 23495_001-020.indd 623495_001-020.indd 6 12/30/05 4:16:29 PM12/30/05 4:16:29 PM 7 The speed of motion can change. If the boy moves his legs more quickly, he will run faster. The direction of motion can change. If the boy on the bicycle turns the handlebars, the bicycle changes direction. Things move at different speeds. Look at the picture. The boy ran for 10 seconds. The other boy pedaled for 10 seconds. Who do you think went faster? Who do you think went farther? The bicycler traveled faster and farther than the runner. 23495_001-020.indd 723495_001-020.indd 7 12/30/05 4:16:30 PM12/30/05 4:16:30 PM 8 Force An object needs a push or pull to move. A push or pull that can make something move is called a force. An object will move in the same direction it is pushed or pulled. It will not speed up or slow down until it is given another push or pull. The more force you use, the farther the box will go! 23495_001-020.indd 823495_001-020.indd 8 12/30/05 4:16:31 PM12/30/05 4:16:31 PM 9 Pushing a wagon gently takes little force. Pushing it harder takes more force. The cart moves farther when you push it harder! It takes more force to move objects farther. It takes more force to move a heavy thing than a light thing. Which wagon takes more force to move? Read the caption to fi nd out! It takes more force to move the wagon with the black dog. 23495_001-020.indd 923495_001-020.indd 9 12/30/05 4:16:33 PM12/30/05 4:16:33 PM 10 Learning About Friction What if you give a cart a push and let it go? After a while, it stops moving. This is because of friction. Friction is a kind of pull. It makes a moving object slow down or stop. The carts slow down because of friction between them and the ground. The girl works against friction to push the carts. 23495_001-020.indd 1023495_001-020.indd 10 12/30/05 4:16:35 PM12/30/05 4:16:35 PM 11 Look at the skaters. The one on the smooth road goes faster than the one on the sand. There is a lot of friction between the skates and the sand. This friction makes the skates slow down. There is less friction between the skates and the road. This allows the skater to go faster on the road. The skater moves fast on the road. The skater moves slowly on the sand. 23495_001-020.indd 1123495_001-020.indd 11 12/30/05 4:16:37 PM12/30/05 4:16:37 PM 12 Learning About Tools and Machines How do tools and machines help us? Tools and machines use pushes and pulls to make things move. Tools and machines can help us do hard things! A hammer is a tool. It uses force to drive in the nail. 23495_001-020.indd 1223495_001-020.indd 12 12/30/05 4:16:39 PM12/30/05 4:16:39 PM 13 See the picture? A wooden spoon is a tool. It pushes the food. It helps mix the eggs and fl our. A truck is a machine. Its engine uses force. The force spins the truck’s wheels. Then it can move the heavy logs. A truck is a machine. A truck helps us move heavy things. The spoon helps mix the meal. It is a tool. 23495_001-020.indd 1323495_001-020.indd 13 12/30/05 4:16:41 PM12/30/05 4:16:41 PM 14 Learning About Gravity Look at the picture. The boy is shooting the ball. What will happen? Will the ball fl oat into the sky? Will it land on the ground? Gravity will pull the ball down to the ground. What is gravity? Gravity is a pulling force. It pulls things toward Earth’s center. When you jump up, you come back down. Gravity is what makes you come back down. Gravity pulls the ball toward the center of Earth. 23495_001-020.indd 1423495_001-020.indd 14 12/30/05 4:16:46 PM12/30/05 4:16:46 PM 15 What does it mean if something is heavy? It means the pull of gravity on that thing is strong. Gravity pulls harder on heavier things. The ball weighs more than the apple. Gravity pulls harder on the ball than on the apple. Gravity pulls harder on heavy things than on light things. 23495_001-020.indd 1523495_001-020.indd 15 12/30/05 4:16:48 PM12/30/05 4:16:48 PM 16 Learning About Magnets What is a magnet? A magnet is a special object that creates a force. Magnets can push some kinds of metal. The letters and numbers on the refrigerator door are magnets. 23495_001-020.indd 1623495_001-020.indd 16 12/30/05 4:16:50 PM12/30/05 4:16:50 PM 17 Magnets attract some metal objects. To attract is to pull toward. Look at the picture. The paper clips are made of metal. The magnet attracts them. Magnets can attract or repel other magnets. To repel is to push away. This magnet has attracted several paper clips. 23495_001-020.indd 1723495_001-020.indd 17 12/30/05 4:16:53 PM12/30/05 4:16:53 PM [...]... pulls things toward the center of Earth the act of moving repel push away 20 Look at the classroom around you Think about position Write to explain the position of at least two things in the classroom Use words such as behind, in front of, left, right, or background 4 motion 3 Cause and Effect You throw a ball into the air What caused it to move? What effect does gravity have on the ball? ... south pole is marked with an S Each magnet has a north pole and a south pole Opposite poles attract each other Like poles repel each other Magnets can move some objects without touching them Look at the picture The magnet is not touching the lock But the magnet is pulling the lock! The magnet attracts the metal of the lock without touching it The N and S on a magnet show where its poles are 18 19 Glossary . Cause and Effect • Captions • Labels • Glossary Forces and Motion Scott Foresman Science 2.1 Standards Preview Standard Set 1. Physical Sciences 1. The motion of objects can be observed and measured slowly on the sand. 23495_001-020.indd 1123495_001-020.indd 11 12/30/05 4:16:37 PM12/30/05 4:16:37 PM 12 Learning About Tools and Machines How do tools and machines help us? Tools and machines. owers. Use meters and centimeters to measure. 1 meter 11 centimeters 23495_001-020.indd 523495_001-020.indd 5 12/30/05 4:16:26 PM12/30/05 4:16:26 PM 6 Learning About Motion Motion is the act