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COPYRIGHT 2003 Science Weekly, Inc.
Look around you! There are wheels everywhere! Two wheels connected with a rod is called a wheel and axle. A wheel and axle is a simple machine.
A machine is something that makes work easier. A bicycle is a machine because riding it is easier than walking. Most machines are compound machines. This means they are made of two or more simple machines working together.
Imagine trying to move a huge block of stone that is too heavy to carry. When 2 surfaces rub together, it is often hard to move them. This rubbing is called friction. It would be very hard to drag this huge stone block along the ground because of friction.
Thousands of years ago, people found that they could move heavy loads by rolling them over tree trunks lying on the ground. Then someone cut an end off of one of these rollers and made the first wheel! Early wheels were made of heavy solid wood. To make wheels lighter, people later cut out the middle and put in spokes instead. After the wheel and axle was invented, it was used in many kinds of transportation. It is still used today.
Gears are simply wheels with teeth (or cogs) around the outside. The cogs on 2 gears can fit together. The gears on a bicycle are easy to see, but most of the time we do not see gears. That's because they are inside of machines. Almost all machines with moving parts have gears inside of them. There are gears inside of clocks, electric mixers, and automobiles.
DID YOU KNOW??
One of the largest bicycles ever built is called the Frankencycle.
It has a front wheel that is 10 feet in diameter.
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Vocabulary
Uni means one. Bi means two. Tri means three. Finish these words.
Use a dictionary to help you.
1) A shape with three corners.
tri--
2) What a police officer wears.
uni--
3) Three babies born at once.
tri--
4) Birdwatchers and sports fans use them to see better.
bi--
Weekly Lab
How do rollers work?
You need: 1 book, 5 straws, masking tape, a ruler.
Step 1: Use the tape to make a START LINE on the table.
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Step 2: Put the front edge of your book on the START LINE. Use one finger to give the book a shove. Measure how far the book went.
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Step 3: Now, put your book on 5 straw rollers. (See the picture.) Repeat Step 2.
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Step 4: Which time did your book go farther? What did the rollers do? Did they make your work easier or harder?
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Weekly Problem
Welcome to WHY-FLY's Bike Shop
1) How many wheels are there in WHY-FLY's Bike Shop? []
2) WHY-FLY gets 2 more bikes and 1 more tricycle, How many wheels are there now? []
3) He sells both tricycles. How many wheels are there now? []
4) WHY-FLY decides to increase his bike supply. He doubles the number of bicycles he has. How many wheels are in his shop now? []
Writing in Science
Imagine a world with no wheels. How would your life be different?
DID YOU KNOW??
Almost 50 million people ride bicycles in the U.S.
DID YOU KNOW??
The wheel is one of the most important inventions ever made.
DID YOU KNOW??
A doorknob is really a type of wheel.
Challenge
A crank is an example of a wheel and axle. The handle of the crank moves in a big circle. It is the wheel. The rest of the crank moves in a smaller circle. It is the axle.
You need: an 8 oz. paper cup, a ballpoint pen, a flexible drinking straw, 12 inches of string, a washer (or other weight), tape, clay
* Use the pen to carefully punch 2 holes through the top of your cup. The holes must be exactly opposite each other. (See the picture.)
* Push your straw through both holes.
* Bend the flexible end of the straw up.
* Tie a washer to the end of the string. Tape the other end of the string to the straight end of the straw. Put a small lump of clay on the end of the straw.
* Slowly turn the flexible end of the straw. This is the wheel. What happens to the axle? Watch what happens to the string and washer as you turn.
Please see Teaching Notes before beginning this activity.
Puzzle
You need: 1
2 sandwich cookies (like Oreos[R]) a shoebox lid
Sandwich cookies are like gears. They are both round with small teeth around their edges.
Place your 2 sandwich cookies along the edge of a shoebox lid. Make sure the cookies are touching! Now, turn the bottom cookie with your fingers. What happens to the other cookie? Which way does it turn?
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Use what you have learned to tell WHY-FLY what direction his last gear will turn. Circle your answer.
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Wheels and-Gear
Background
Since the time people began to roam the Earth, we have always tried to make work easier. All work involves motion or movement. As Aristotle taught, an object will not move unless something is pushing or pulling it. In other words, an object will not move unless a force is acting upon it. A force can be either a push or a pull.
In scientific terms, work is the amount of force that is applied to an object to move it a certain distance. This means that work equals force times distance. A machine makes work easier by changing the size or the direction of the force that is applied. People soon discovered that by building machines, they could ease their workload.
Some machines are so simple that they do not really seem to be machines. In fact, 6 of them are called simple machines. They are the wheel and axle, the lever, the wedge, the pulley, the inclined plane, and the screw. Most machines are far more complex in...
Read the full article for free courtesy of your local library.
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