Centripetal Force – Tornado in a Bottle

Centripetal Force – Tornado in a Bottle

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A couple weeks ago we learned about centripetal force when we did the Hex Nut Balloon experiment. We learned that centripetal force is what makes an object move in a spiral pattern when it is travelling in a circle, like a penny in a funnel shaped wishing well. 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”.

Today, we are going to learn about how liquid and air behave when they are moving in spiral pattern. 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 forceWhat You Need:

  • 2 Liter Soda Bottles
  • Duct Tape
  • Water
  • Food Coloring (Optional)

The tornado in the bottle looks a lot like the water draining out of the bathtub. When liquids pour they make a spiral pattern around a center. This is called a vortex. Gravity is pulling the liquid down toward the hole while the force of the pouring water is rotating around a center point…the middle of the drain or the neck of the liter bottle.

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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.

Vortex – Whirling liquid or gas, like a tornado or the water draining out of a bathtub.

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4 Responses »

  1. Bad Science. There is no such thing as Centripetal Force. There are a combination of other forces at work which give the ILLUSION that there is another force at work.

  2. well, on a force diagram centripetal force isn’t supposed to be drawn. the way it works is that acceleration is pointed inwards and velocity is pointed tangent. the centripetal force is a result. it is actually a force that goes inwards, not in circles. you did define that correctly. i’m pretty sure this is okay. the CENTRIFUGAL force, on another hand, does not exist.

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