Materials and Making Things
Primary 2 · Science and Elementary Technology
Materials and Making Things
Lesson 3 of 3
15 min
Let's begin
It is a windy afternoon in Kigali. Byiringiro is walking home when an old plastic bag lifts off the road, climbs into the air and spins round and round above his head.
He cannot see the wind. But he can see what the wind does. Today you will build something that the wind will spin for you — a paper windmill. Then you will find out exactly why it turns.
Good makers think before they cut. Here is everything you need. Find it all first, and put it on the table.
Thin paper is best. Thick card is heavy, and heavy blades turn slowly.
Your book page is a rectangle: long one way, short the other. A windmill needs a square, where every side is the same.
Look at your square. Each corner has been split into two sharp points. Count them all: eight points. And the middle is still whole, holding everything together.
Warning
If you cut right through the centre dot, your square falls apart into four loose pieces and the windmill is finished before it began. Stop two fingers early. The centre must stay uncut.
This is the step that makes it spin. Read it slowly.
Now four points are stacked on the centre, under your thumb, and four points are still sticking out as corners. Your thumb is doing all the work — do not let go.
Why always the left one? Because every blade must lean the same way round. If you bend a left point, then a right point, the blades lean against each other. One pushes forwards, one pushes backwards, and the windmill stands still and sulks.
Now call an adult. The pin is sharp.
Hold the pencil. Blow at the windmill from the front. It should turn.
Now take it outside. Hold it up high and let the wind find it. Or run with it — when you run, you make your own wind.
The wind is moving air. You cannot see air, but you can feel it push against your face.
Your four bent points are the blades. Each one is a little scoop, tilted to one side.
When moving air arrives at a blade, it cannot slip straight past — the tilted scoop is in the way. So the air pushes the blade sideways.
Every blade is tilted the same way, so every blade is pushed the same way round. Push, push, push, push — and the paper turns.
And if you had left the points flat? The air would slide straight past, hit nothing, and push nothing. The tilt is the whole secret.
Do not throw it away. Every maker fixes things. Look for the reason:
| What you see | The reason, and the fix |
|---|---|
| It will not turn at all | The pin is too tight. Pull it back a little, so the paper is free to move. |
| The square fell into four pieces | You cut through the centre. Cut a new square, and stop two fingers early. |
| It turns, then stops | The points are pressed flat. Lift them so they curve like scoops again. |
| It is slow and heavy | Your paper is too thick. Use a thin page instead. |
| It tears at the pinhole | Put a small square of tape on the centre before you pin it. |
Somewhere in the world, right now, there are windmills taller than the tallest tree. The wind pushes their huge tilted blades, they turn, and they make electricity for whole towns.
Yours is made of paper and it fits in your hand. But it works in exactly the same way.
When you finish, tidy up. Give the pin back to the adult, pick up every scrap of paper, and put the scissors away closed.
Tip
Two rules save every windmill. Same side, every corner — take the left point four times, never a right one. And leave a little gap at the pin, so the paper can turn. Tight pin, no spin!
Think about each one. Then check your answer below.
What you learned today
Quick check
Make a windmill. Put the steps in order.
Tap the cards in the right order.
