BOATS

Although boats float, their weight makes them settle a little way into the water. This means they create some resistance or drag when they move through the water. The bow (front) of a boat is V-shaped and curved. This raises the boat up as it goes faster, and helps reduce drag. Boats are powered by sails, oars, or engines that turn propellers at the rear. The propellers push water backwards, and this backward thrust moves the boat forwards.

HYDROFOIL

A hydrofoil is a high-speed boat that seems to fly along almost out of the water. The boat has small underwater wings called foils. These work like the aerofoil wings of an aeroplane. As the boat speeds along, the foils generate a force upwards that lifts its hull (body) clear of the water. This reduces drag and helps the hydrofoil go faster.

SUBMARINES

Submarines can float on the sea, sink just beneath the surface, or dive to the seabed. They dive or surface using tanks that work like a fish’s swim bladder. When the tanks are filled with water, the submarine dives. When they are filled with air, it surfaces. A submarine can select its level in the sea by changing the mixture of air and water in its tanks.

Copyright © 2007 Dorling Kindersley

highlights

Teens and E-Cigarettes: 6 Things You Must Know
For the first time in a generation, tobacco use has risen among the nation's youth, due to the rising use of e-cigarettes. Learn more about the dangerous and addictive e-cigarette trend, and get tips to talk to your teen.

Find Today's Newest & Best Children's Books!
Looking for newly released books for your child? Try our new Book Finder tool to search for new books by age, type, and theme, brought to you by Galactic Hot Dogs.

Printable Lists of the Top 100 Baby Names
Need help with baby name ideas? Use our printable list of the top 100 girl names and top 100 boy names of 2015 to help you brainstorm and narrow down your favorites.

Registered for Kindergarten — Now What?
Wondering what to do now that you've signed your child up for kindergarten? Try our award-winning Kindergarten Readiness app! This easy-to-use checklist comes with games and activities to help your child build essential skills for kindergarten. Download the Kindergarten Readiness app today!

stay connected

Sign up for our free email newsletters and receive the latest advice and information on all things parenting.

Enter your email address to sign up or manage your account.

Facebook icon Facebook icon Follow Us on Pinterest

editor’s picks