Centripetal Acceleration Vortex Whirlpool Bottle

30 mins Ages 10-14 Indoor

A challenging, hands-on discovery and STEM project designed for curious young minds aged 10 to 14.

Materials Needed

  • • Clear plastic 2-liter soda bottles (2 matching units)
  • • Metal fender washer (approx. 1-inch diameter with 3/8-inch center hole) (1 unit)
  • • Heavy-duty duct tape or silicone self-fusing tape (1 roll)
  • • Water and food coloring (1 set)

Pro Tips

  • → Inverting the bottles without swirling causes water to glug slowly due to air pressure lock.
  • → Swirling the top bottle in a circular motion creates a rotating vortex that opens a central air core, allowing air to rise while water drains rapidly.
  • → Drop small floating beads or glitter into the water to trace rotational streamline velocities.

Safety First

Wrap the center connection securely with waterproof tape to prevent leaks.

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Step-by-Step Instructions

1

Step 1

Fill one 2-liter soda bottle two-thirds full with water and add 2 drops of food coloring.

2

Step 2

Place a metal washer with a 9 mm hole over the bottle mouth, set an empty identical bottle upside down on top, and align the rims.

3

Step 3

Wrap the junction tightly with multiple overlapping layers of waterproof duct tape to create an airtight seal.

4

Step 4

Flip the assembly upside down, swirl the top bottle in vigorous horizontal circles, and watch a vortex funnel form in the water.

What they are learning

Centripetal acceleration and angular momentum Vortex air-core displacement dynamics Hydrodynamic drainage fluid resistance