The Swiss Family Robinson tells of the adventures of a family that is shipwrecked on an uninhabited island. The story was made up more than 180 years ago by a real Swiss family. They imagined they...
Ups and downs
Suppose someone asked you to lift a hippopotamus out of its hippopotamus-sized bathtub! It sounds impossible---but with a simple machine called a pulley, you could do it! A pulley is a special kind...
What am I?
The answers to all of these riddles are wheel-and-axle machines. Can you find two that roll and two that turn? \_ > 1\. My axles are two, but my wheels are three. Even little kids ride > on me. > >...
Turn, turn, turn
How many wheels do you use in a day? You can count wheels that roll---bicycle wheels, car wheels, and bus wheels, too. They help you get places. A push from you or an engine makes the axle turn. And...
Rolling along
Four wheels, a box, and a handle. That's all a wagon is. But with a wagon you can easily carry a couple of friends or a load of empty bottles---or even give the dog a ride. When you use a wagon, a...
The shape of a screw
Wham! Wham! Wham! All it takes to nail two pieces of wood together is a few strong hits with a hammer. But fastening two pieces of wood together with a screw is a lot harder. The screw has to be...
A shape that works
Be careful---that knife is sharp! Don't stick yourself with that needle! Working with sharp things means taking special care. But some things have to be sharp to work well. A dull knife or a needle...
Slides and steps
Is a slanted board a machine? It is if you use it to do some work. It's a kind of simple machine called an inclined plane. Inclined means \"slanted," and a plane is a flat surface. So an inclined...
Make an alligator long-arm
Levers make it easier to lift big and heavy things. They can also help you pick up things you can't quite reach. This alligator long-arm uses pairs of levers to make other levers move. Use the ruler...
A lever is clever
How many times can you lift your best friend higher than your head? How many times can your best friend lift you? It doesn't sound easy, but it is---and it's fun, too. When you and your friend are...