How can a 50-pound boy lift a 200-pound man? How does a wheelbarrow work? Is it easier to roll a toy truck up an inclined plane or just pick it straight up? What is an easy way to move a load of bricks? The experiments in this book will show how simple machines work and explain some simple principles of physical science. All readers need are some simple materials, most of which can be found around the home, school, or neighborhood.