Turn the key at the back of the alarm clock once . . . twice . . . three times. At first the key turns easily. But as you keep winding, the key turns harder and harder. Finally the clock is wound as...
The moving stairs
> Here I stood on the floor below, Then on a stair-step rising slow. > > Over the heads of the shoppers then--- Dressed-up ladies and bothered > men; > § > > An escalator that carries you from...
Machines from machines
It's easy to see how a pair of scissors works. Every time you squeeze the handles together, the blades cut into the paper. Using a pair of scissors is simple---but scissors are not a simple machine....
Finding out about gears
Materials - cardboard box - corrugated packing paper - marker - pins (3 long) - plastic lids (1 small, 2 large) • white glue What special things can gears do? Here is a project that will help...
Wheels with teeth
Why should a wheel have teeth? Wheels don't eat! But some wheels use teeth to get a lot of work done---and they can do things that other wheels can't do. > A wheel with teeth is called a gear....
The Tree House
by Johann Wyss We soon found four large casks, made of sound wood and strongly bound with iron hoops. These were floating with other things in the water in the hold. We managed to fish them out and...
The Swiss Family Robinson
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...
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