Addison Wesley Science & Technology Grade 4 Pulleys & Gears

In this unit, you will learn about two special kinds of wheels: pulleys and gears. Pulleys and gears play an important part in our lives. Even when we can’t see them, they are in machines all around us. They help us to get where we’re going (in bus and car engines, and bicycles). They keep us on time (in watches and clocks). They make tasks easier (in eggbeaters and cranes). They even allow us to skip the stairs once in a while (in escalators and elevators).