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Have you ever put a coin in one of those wishing wells that is shaped like a giant funnel? The coin rolls around and around the sides of the funnel in smaller and smaller circles until it goes down the hole in the middle of the well? That coin is demonstrating centripetal force. Centripetal force is the force that pulls a thing toward the center of rotation….like the little whirlpool that forms when you drain the bathtub or like the Zinga at Holiday World! Why IS that water slide called Zinga? Because in Swahili Zinga means “to move in a circular motion”. Lots of amusement park rides work because of the laws of physics.
You can use a balloon to demonstrate centripetal force.
What You Need:
- Balloon
- Hex Nut
Blow up a large balloon. Before you close the balloon, put a hex nut in it and then tie the end of the balloon closed. Hold the balloon between your hands and move it in a circular motion until the hex nut starts to roll around the inside of the balloon. Now stop moving the balloon and watch what happens to the hex nut. What you are seeing is centripetal force. The hex nut is on a circular path inside the balloon. Things that are moving in a curved or circular motion will slowly move toward the center of the circle, in this case, the bottom of the balloon. What sound does the hex nut make? How about a penny? A marble? Try them all and see how they behave the same or differently.
Here are some websites that will help you look at centripedal force and other physics laws that make amusement park rides work the way they do:
- Steve Spangler Science: Screaming Balloons
- PBS Kids: Fetch Whaohler Coaster
- Funderstanding Roller Coaster Demonstration
- Roller Coaster Physics: Design a Roller Coaster
Here are some books that will help you demonstrate Centripedal force and learn more about it:
- Google Preview: Naked Eggs and Flying Potatoes: Screaming Balloon(Pages 136-139)
- Google Preview: Super Simple Things to Do With Balloons: Let’s Go Nuts! (pages 10-11)
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Words to Know:
Centripetal Force – A force that makes an object move in a circular path toward the center around which the object is moving. It is the force that pulls a thing toward the center of rotation.
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