SIMPLE. MACHINES by Wiley Blevins

Transcription

1 SIMPLE MACHINES by Wiley Blevins

2 SIMPLE MACHINES by Wiley Blevins

3 Copyright MONDO PUBLISHING All rights reserved. Every effort has been made to trace the ownership of all copyright materials in this book and to obtain permission for their use. No part of this publication may be reproduced, except in the case of quotation for articles or reviews, or stored in any retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without written permission from the publisher. For information contact: MONDO Publishing 980 Avenue of the Americas New York, NY Visit our website at Printed in Guangzhou, China Nordica International Ltd., Credits: p. 4: Andresr/Shutterstock; p. 5: pressmaster/123rf Stock Photo; p. 8: Christina Richards/Shutterstock; p. 9: laures/123rf Stock Photo; p. 10: (top) luther2k/123rf Stock Photo, (bottom) Lurin/Shutterstock; p. 11: (top) AnaBGD/123RF Stock Photo, (bottom) kobyakov/123rf Stock Photo; p. 12: (top) victoriakh/shutterstock, (bottom) Kiko Jimenez/Shutterstock; p. 13: (top) Dan Kosmayer/Shutterstock, (bottom) bergamont/shutterstock; p. 14: Susan Montgomery/Shutterstock; p. 15: Igor Shootov/ Shutterstock; p. 16: kyolshin/123rf Stock Photo; p. 17: Shi Yali/Shutterstock; p. 18: ljupco/123rf Stock Photo; p. 19: (top) alexandrmoroz/123rf Stock Photo, (center) Nordling/Shutterstock, (bottom) gresei/shutterstock; 20: (top) alexandrmoroz/123rf Stock Photo, (bottom) clark_fang/istock Photo; p. 21: lsaloni/123rf Stock Photo; p. 22: (top, left) Ingvar Bjork/Shutterstock, (bottom, left) Zigzag Mountain Art/Shutterstock, (right) Roland Ijdema/Shutterstock. ISBN

4 Table Of Contents What Is Work?...4 Simple Machines...6 Inclined Plane...8 Lever...9 Wedge...10 Screw...12 Pulley...14 Wheel and Axle...16 Complex Machines...18 Simple Machines Are Everywhere..22 Glossary...23 Index

5 4 What Is Work? Most people think of work as a job or a way to earn money. But when scientists talk about work, they mean many things. Pick up a heavy box. Ride a bike. According to a scientist, you are doing work!

6 Do you know what force is? Force is the power to get work done. You use force when you lift a heavy box, bang a drum, or throw a ball. But what you do is only work if you get something done. Try pushing a book across the table. Did it move? Yes? Then you did work. Now try pushing a wall. Did it move? No. You might be tired, but you didn t do work. Machines help us do work. They can make our work easier and faster. 5

7 Simple Machines Some machines, like cars and clocks, have many moving parts, while other machines have only a few or no moving parts. These are called simple machines. There are six types of simple machines that help us do work every day. Let s take a closer look. inclined plane lever 6

8 wedge pulley screw wheel and axle 7

9 Inclined Plane An inclined plane is a flat, slanted surface. Imagine lifting a box high into a truck. That s not so easy. But you could slide the box up, or walk up, an inclined plane into the back of the truck. This would take less work and use less force. A wheelchair ramp is an important inclined plane. It helps people who can t climb steps by allowing them to easily glide up or down the ramp. 8

10 Lever A lever is basically a long stick that you place on a fulcrum to move something. Here s how it works. Put one end of the lever under a big rock. Then push down on the other end. lever The end under the rock moves up! The force moves the rock in the opposite direction. This is easier than trying to lift the rock with your hands. fulcrum A seesaw is a lever, too. You push up with your legs, and your friend goes down. You use force to change the direction your friend moves. What fun! 9

11 Wedge A wedge is a simple machine used to cut or split things. An axe is a wedge. When you hit wood with the axe, the wood on either side of the axe splits apart. Farmers use wedges, called plows, to cut and split apart the soil. Then the farmer can plant seeds to grow crops. 10

12 You use wedges at school. The little metal blade in a pencil sharpener is a wedge. It cuts away parts of your pencil so you can write. Did you know you have wedges inside your mouth? That s right! Your front teeth are wedges. They cut and split apart food. Take good care of these pearly white machines. The front teeth that cut into food are called incisors. The front teeth that cut into food are called incisors. 11

13 Screw A screw is a machine that holds things together, such as two pieces of wood. Look closely at the screw. Do you see the raised ridges curved around it? These are called threads. It takes less force to get a screw into a piece of wood than a nail. You would have to hit a nail very hard. However, twisting a screw into the wood takes less work and less force. 12

14 You might not think you use screws every day, but you do. A jar with a twist-off lid is a type of screw. Without it, the lid would come off and your peanut butter or jelly wouldn t stay fresh. The bottom of a light bulb is a screw, too. It has threads curving around it that hold the light bulb in the socket. Otherwise, it would fall onto the floor. Crash! 13

15 Pulley Do you know what a pulley is? You have seen a pulley when looking at a flagpole. A pulley is made with a wheel and rope. A pulley changes the direction of a force. If you pull down the rope on a flagpole, the other end of the rope pulls up the flag. This is much easier than climbing the flagpole! To show respect for the U.S. flag, it cannot touch the ground when it is being lowered. 14

16 The pulleys help these teenagers adjust the sails in order to increase the speed of boat. We often use pulleys to move things that are heavy. People use pulleys to lift the sails on a boat. An elevator is also a pulley. You don t see the ropes and wheels while you are inside the elevator, but they help to move the elevator from one floor to another in a tall building. 15

17 Chariots were used by the ancient Romans as transportation. A chariot had a platform and wheels. Axle Wheel Wheel and Axle Many people think the wheel is the most important machine of all time. Before the wheel, people had to push or pull heavy objects. With wheels, they could roll objects long distances with less work. Any machine with parts that move in a circle uses wheels. The larger wheel turns on a smaller wheel, called an axle. 16

18 Perhaps everyone s favorite wheel is the Ferris wheel. Hop on, spin around, and enjoy the view! 17

19 Complex Machines A complex machine is a machine that is made up of more than one simple machine. The simple machines work together to make work easier. Cars and bicycles are examples of complex machines. You can see some of the different simple machines that you have read about by looking at a bicycle. A bicycle has wheels and axles that move the bike along. The handlebars, handbrakes, and brake pedals are all types of levers. Many bikes also have gears that allow the rider to change the turning force. You can change the gears to make it easier to ride a bike up an inclined plane. lever wheel and axle 18 wheel and axle

20 Here are some more examples of complex machines. Complex Machine Simple Machines wheel and axle lever wheelbarrow wedge lever stapler wheel and axle wedge lever can opener 19

21 A wheelbarrow is made up of two simple machines. It has long handles that act as levers and rolls on a wheel that acts as a wheel and axle. lever A stapler is also made up of two wheel and axle simple machines. The staples in a stapler are wedges because they pierce through paper. The top arm of the stapler is a lever that moves up and down when you have to open it to add more staples. lever wedge 20

22 Some complex machines are made of three simple machines. An example of this is a can opener. First there is the wheel and axle in the top part of the can opener. Then there is the wedge, which is the part that slices open the can. And that leaves the third part. The two arms of the can opener are levers that help you open the can. lever wheel and axle wedge 21

23 Simple Machines Are Everywhere Simple machines are all around us. Look in your classroom or at home. They make our work easier, but they aren t so simple when you take a closer look at them. What simple machines do you use? 22

24 GLOSSARY force a push or pull fulcrum the point on which a lever is supported and on which it pivots platform a raised level surface on which people or things can stand plow a large farming tool with one or more blades fixed in a frame, drawn by a tractor or by animals and used for cutting into the soil and to prepare for the planting of seeds ramp a flat surface that is slanted sail a piece of material extended on a post to catch the wind and move a boat or ship simple machine a mechanical object with few or no moving parts (examples: inclined plane, lever, pulley, screw, wedge, wheel and axle) work using force to move an object 23

25 INDEX complex machines, force, 5, 18 inclined plane, 6, 8, 18 lever, 6, pulley, 7, screw, 7, wedge, 7, 10 11, wheel and axle, 7, work, 4 5

26 What is a force? How can a simple machine help you move a heavy object? Can an object be made of more than one simple machine? Read this book to find out the answers to these questions and more about how simple machines work.