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Water Bottle Fountain

  • A plastic, one-liter bottle with three holes
  • Three push pins to plug the holes
  • A bottle cap
  • A shallow basin
  • Procedure: Use the pins to puncture three holes in the bottle. Fill the bottle with water and allow it to flow out of the bottle. If you cap the bottle, you can stifle the flow. You can also squeeze the capped bottle to demonstrate increasing the pressure above the water.

    Explanation: The static pressure in the bottle increases with depth due to the weight of the water. At any one of the holes, the difference between the local static pressure and the ambient pressure forces the water out the hole and the gravitational force then causes it to arc downward. The lower the hole, the higher the static pressure and therefore the faster the exiting flow (Bernoulli's equation). However, the lower holes are also closer to the ground and therefore will hit the ground sooner than the slower flows higher up. One can calculate the optimum hole location by balancing the exit speed (from Bernoulli) with the distance it has to fall before it hits the ground (using ballistics).

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