Briefly describes simple machines, machine parts, and the powers that move them.

Depicts a variety of very large machines, including tower cranes, a dockyard crane, an oil production platform, and a concrete silo.

"This excellent addition to the ever popular Questions & Answers series lifts the flap on all kinds of gadgets, systems and ideas. It answers questions such as How does electricity get into our walls? Why do waves go up and down? and Where does money come from? Perfect for every inquisitive child"--Publisher's description.