Screws
How can we lift and lower things? How can we move heavy loads from one place to another? By using simple machines! Wheels, wedges, levers, pulleys, screws, and inclined planes are the simple machines that help us do work. In this series, students will discover how to use them each day to make life easier. Additional features to aid comprehension include a table of contents, a phonetic glossary, informative sidebars, sources for further research, an index, and an introduction to the author.