Materials Needed:
- Square piece of paper or thin cardstock (about 6x6 inches or 15x15 cm)
- Scissors
- Pushpin or brad fastener
- Pencil with an intact eraser on top (or a thin wooden dowel)
- Ruler
- Optional: Crayons or markers for decorating
- Optional: Small electric fan for testing
Introduction: Whirling Wonders!
Have you ever seen a tall tower with big blades spinning in the wind? Those are windmills or wind turbines! For centuries, people have used windmills for important jobs like grinding grain into flour or pumping water. Today, modern wind turbines use the wind's power to make electricity. But how do they actually *work*? It's all about physics!
What is Wind?
Wind is simply air in motion. Air might seem like nothing, but it's made of tiny particles called molecules. When these molecules move together in one direction, we feel it as wind. Moving things have energy called kinetic energy. So, wind is moving air, and it carries kinetic energy.
How Windmills Capture Energy
Think about blowing on a pinwheel. It spins, right? Windmills work in a similar way, but on a much larger scale.
- Catching the Wind: Windmills have large blades, also called sails. These blades are specially shaped, often curved like an airplane wing. When the wind blows, it pushes against the surface of the blades.
- Making Things Turn: Because of their shape and angle, the wind pushes the blades, causing them to rotate. All the blades are connected to a central hub. When the blades spin, the hub spins too. The blades and hub together are called the rotor.
- Energy Transformation: This is the coolest part! The windmill takes the kinetic energy (movement energy) from the wind and transforms it into mechanical energy (the energy of the spinning rotor). This spinning motion can then be used to do work – like turning a shaft to grind grain, pump water, or spin a generator to make electricity.
Parts of a Simple Windmill
- Blades/Sails: Catch the wind and start the rotation.
- Rotor: The spinning part, including the blades and the central hub.
- Tower: The structure that holds the rotor high up where the wind is often stronger.
- Nacelle (in modern turbines): A housing on top of the tower that holds the machinery like gears and generators (we won't build this part today).
Activity: Build Your Own Pinwheel!
Let's build a simple model to see these principles in action.
- Prepare the Square: If you like, decorate your square piece of paper now.
- Mark the Center: Use a ruler to lightly draw diagonal lines from corner to corner. The point where they cross is the center. Mark it with a dot.
- Cut the Lines: Cut along each diagonal line from the corner towards the center, stopping about half an inch (or 1 cm) away from the center dot. Do NOT cut all the way to the middle!
- Fold the Points: Pick up one corner tip from each of the four cut sections (pick every other point). Carefully bend these points towards the center dot, overlapping them slightly.
- Fasten: Carefully push the pushpin through the overlapping points and then through the center dot of the paper.
- Attach to Pencil: Push the sharp end of the pushpin into the eraser on top of your pencil. Make sure the pinwheel isn't pushed too tightly against the eraser, so it can spin freely.
Experiment Time!
Gently blow on your pinwheel. What happens? It spins! You've just used the kinetic energy from your breath (moving air) to create mechanical energy (the spinning pinwheel). Blow harder. Does it spin faster? Try blowing from different angles. Now, if you have a small fan, try holding your pinwheel in front of it (on a low setting, with adult supervision). This mimics how a real windmill uses the natural wind.
Conclusion
Windmills are amazing machines that harness the power of the wind. They work by capturing the wind's kinetic energy with their blades and transforming it into useful mechanical energy. From ancient grain mills to modern wind turbines generating electricity, they are a fantastic example of physics in action and an important source of clean, renewable energy!