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Windmill: What Kind of Machine is a Windmill, and How Does it Help You to do Work?

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Author: Janice VanCleave

Problem

What kind of machine is a windmill, and how does it help you to do work?

Materials

  • Scissors
  • Ruler
  • Sheet of typing paper
  • Pencil
  • Large coin (quarter)
  • Paper hole-punch
  • Drinking straw
  • Modeling clay
  • Sewing thread
  • Paper clip

Procedure

Windmill

Windmill

  1. Cut a 6-inch × 6-inch (15-cm × 15-cm) square from the sheet of paper.
  2. Draw two diagonal lines across the paper square so that you have an ''X.''
  3. Use the coin to draw a circle in the center of the square.
  4. With the hole-punch, make one hole in each comer of the square as indicated in the diagram.
  5. Make a hole through the center of the circle with the point of the pencil.
  6. Use the scissors to cut the four diagonal lines up to the edge of the circle in the center.
  7. To form a paper wheel-of-sails, fold the comers with the holes over the center, one at a time, aligning all the holes with the hole in the center of the paper.
  8. Push a drinking straw through the holes, and position the paper wheel in the center of the straw.
  9. Wrap a small piece of clay around both sides of the straw next to the paper wheel to keep the wheel in place.
  10. Cut a 2-foot (60-cm) piece of sewing thread.
  11. Attach one end of the thread about 2 inches (5 cm) from one end of the straw.
  12. Tie the free end of the thread to the paper clip.
  13. Hold your hands upright in front of your face, with your thumbs pointing toward your body.
  14. Cradle the ends of the straw in the grooves formed between your index fingers and thumbs. Do not grip the straw.
  15. Blow toward the paper windmill.
  16. Observe the movement of the paper wheel, straw, and paper clip.

Results

The paper wheel and the straw turn. The string attached to the straw winds around the turning straw, and thus the paper clip rises.

Why?

The paper wheel and the straw form a simple machine called a wheel and axle (a large wheel to which a smaller wheel or axle is attached). Connecting the thread and paper clip produces a model demonstrating how a windmill works. The paper sails of the model windmill act as a wheel and turn in a large circle; the straw is the axle and turns in a smaller circle. The wheel and axle turn together, but the wheel makes a bigger circle than the axle does. As the wheel makes one large turn, the string winds once around the turning axle; the load (the paper clip) rises a distance equal to the distance around the axle. It takes less force to raise the load (the paper clip) by turning the larger wheel than by lifting the load with your hands.

Let's Explore

  1. Does the size of the wheel affect the results? Repeat the experiment twice, each time changing the size of the paper wheel. First construct a wheel using a 3-inch × 3-inch (7.5-cm × 7.5- cm) square, and then construct a wheel using a 12-inch × 12-inch (30-cm × 30-cm) square.
  2. Would a different-size axle affect the results? Repeat the original experiment using a knitting needle for a smaller axle. Repeat again using a dowel rod with a circumference larger than that of the straw.
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