ImageAirplanes are a relatively recent invention. The first one flew just over 100 years ago. As little as 50 years ago, only small numbers of people had ridden in an airplane. Today, air travel is one of the most common means of transportation.

Hundreds of thousands of people fly on airplanes each year. You buy your ticket. You pack your suitcase. Then, off you go to the airport.

The airport is where planes take off and land. An agent takes your suitcase. You go to a gate (loading and unloading area) and get on your plane. There are rows and rows of seats. You sit down next to a window. You fasten your seat belt. You are ready to take off.


ImagePeople in the 1800s didn’t know what to think about a new invention called the automobile. No one was sure it would catch on. In those days, people often traveled in carriages pulled by horses. So when the first automobiles appeared, people nicknamed them “horseless carriages.”

The first automobiles looked a lot like horse carriages. That was the style people knew. But the automobile soon took on a look that was all its own. The modern automobile has a hood and fenders.

It has a roof, sides, and four wheels. It has seats where the driver and passengers sit. Modern automobiles are commonly called cars or autos.


ImageWhat do you think the first bridge looked like? If you said a log or tree trunk across a river, you’re probably right. That’s what the experts think.

People might also have crossed a stream in early times by stretching a few vines across it. They could walk on the lower vines and hold onto the top vines for balance.

These bridges wouldn’t have lasted long. A raging river could carry away a log bridge. Vines could rot or break. Bridges nowadays are much stronger.


ImageRiding a bicycle is a great way to get around. Bicycles are quiet, fun to ride, and you don’t need gas or electricity to make them go. You just use the power of your legs!

Bicycles have two wheels. One wheel is in front of the other. You swing your leg over the bike, sit down, and start pedaling.


The heart of every bicycle is its frame. Most bicycles have frames made of thin metal tubes. The best frames are light and strong. A seat, called a saddle, is in the middle of the frame. You can make the seat higher or lower.

Engines and Motors

ImageWhat do a toy car, a blender, a jet plane, a tape recorder, a refrigerator, a lawn mower, a fan, a helicopter, a printing press, an electric drill, and a speeding train all have in common? They contain an engine or motor.


An engine is a machine that makes energy more usable. Engines usually turn heat energy into motion.

Think of a roaring campfire. The fire puts out lots of energy. The fire’s energy may keep you warm, but it won’t take you to soccer practice. An engine can take heat energy and turn it into motion.