Materials Required:
Straw
Pencil (with a good eraser)
Straight pin
Tape (duct tape recommended)
Balloon
Steps Involved:
Prepare the Balloon and Straw:
Attach the balloon to one end of the straw using duct tape. Ensure the tape creates a tight seal around the straw to prevent air from escaping.
Attach the Straw to the Pencil:
Find the balance point of the straw with the attached balloon by balancing it on your finger. Once located, insert a straight pin just past the tape on the straw, and then push the pin into the pencil’s eraser.
Blow Up the Balloon:
Blow into the free end of the straw to inflate the balloon. It may require some effort, but it’s manageable for children. Once inflated, hold the end of the straw to keep the air inside the balloon.
Observe the Pinwheel in Action:
Release the straw and observe the balloon as it deflates. The escaping air causes the straw to spin around the pencil, creating a pinwheel effect. Notice that the balloon spins faster as it deflates.
Discuss the Science Behind It:
Explain that this experiment demonstrates Newton’s third law of motion, which states that for every action, there is an equal and opposite reaction. The air rushing out of the balloon pushes the straw in the opposite direction, causing it to spin.
Discuss how the pin in the eraser creates centripetal force, which helps maintain the circular motion of the straw as it spins.
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