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Rocket Pinwheel

SUBJECT: Rocketry

TOPIC: Action-Reaction Principle

DESCRIPTION: Construct a balloon- powered pinwheel.

CONTRIBUTED BY: John Hartsfield, NASA Glenn Research Center

EDITED BY: Roger Storm, NASA Glenn Research Center

## MATERIALS:

• Wooden pencil with an eraser on one end
• Sewing pin
• Round party balloon
• Flexible soda straw
• Plastic tape

## METHOD:

1. Inflate the balloon to stretch it out a bit.

2. Slip the nozzle end of the balloon over the end of the straw farthest away from the bend. Use a short piece of plastic tape to seal the balloon to the straw. The balloon should inflate when you blow through the straw.

3. Bend the opposite end of the straw at a right angle.

4. Lay the straw and balloon on an outstretched finger so that it balances and mark the balance point. Push the pin through the straw at the balance point and then continue pushing the pin into the eraser of the pencil and finally into the wood itself.

5. Spin the straw a few times to loosen up the hole the pin has made.

6. Blow in the straw to inflate the balloon and then let go of the straw.

DISCUSSION: The balloon-powered pinwheel spins because of the action-reaction principle described in Newton's Third Law of Motion. Stated simply, the law says every action is, accompanied by an opposite and equal reaction. In this case, the balloon produces an action by squeezing on the air inside causing it to rush out the straw. The air, traveling around the bend in the straw, imparts a reaction force at a right angle to the straw. The result is that the balloon and straw spins around the pin.

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