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

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 Twitter icon Follow Us on Pinterest

editor’s picks

highlights

Join BIC on our mission to save handwriting and Fight For Your Write! Writing helps kids become better readers, boosts their confidence and sparks their creativity. Visit BICFightForYourWrite.com to sign our petition to save handwriting!

7 Fun Driveway and Sidewalk Games for Kids
Looking for classic outdoor games kids can play in the driveway or on the sidewalk, just like the good ol' days? From hopscotch to bubble-blowing contests, there's something for all ages!

Kindergarten Readiness App Wins Gold
Our Kindergarten Readiness app won the Gold Award of Excellence in the educational category at the 2014 Communicator Awards. This valuable checklist comes with games and activities to help your child practice the essential skills she needs for kindergarten. Download the Kindergarten Readiness app today!

Best Sun Safety Practices for Babies
Follow these sun safety practices for babies to ensure your little one stays safe on the beach and on sunny days all year long.