How Things Work Cars, Bikes, Trains, and Other Land Machines

Grade 3-5-- The subjects of wheeled vehicles and floating machines are treated in omnibus fashion in these two useful but densely packed titles. A one-page illustrated timeline of "famous firsts" and an introduction are followed by spreads depicting such topics as "Drum and Disc Brakes" or "Hydrofoils." Sidebars focus on particular aspects, such as (in Boats ) knots, water jets, ballast; and (in Cars ) friction, combustion, or compression. Several boxes present things to do, such as making a water-jet boat from a balloon and a large plastic bottle. These "Test It Out" projects are more inviting in Boats than in Cars , which merely illustrate principles without rewarding children with toys as well. Full-color diagrams are labeled, and line drawings and closeups detail the workings of these machines. Technical vocabulary is defined and reused, making the books challenging for readers used to sampling rather than reading front to back.