======Water Bottle Pressure Demo======


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**Safety: **{{$demo.safety_description}}\\
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**Alternative titles:** Three Holed Water Bottle
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====Summary====                   
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====Procedure====  
  - Use scissors or a drill to make three small, evenly spaced holes vertically along the side of a plastic bottle.
  - Cover the holes with tape and fill the bottle with water to the top; screw on the cap.
  - Place the bottle in a sink or outdoors to contain the water.
  - Predict how water will flow when the tape is removed — which hole will spray farthest?
  - Remove the tape and then unscrew the cap to let air replace the escaping water.
  - Observe that water from the lowest hole shoots out farthest, showing greater pressure at greater depth.




====Links==== 
Observing the Effect of Water Pressure - Next Generation Science: 
{{youtube>YtdEN-40tUI?}}\\

How water pressure changes with depth ~ Water bottle demonstration - Physics Rox by Ms Hoo: 
{{youtube>uXZi5Fw3Ytk?}}\\

📄 How does pressure change with depth? - Encounter Edu: [[https://encounteredu.com/take-action/how-does-pressure-change-with-depth]]\\


====Variations====
  * Try bottles of different sizes to compare the effect of overall height of water.
  * Use food coloring in the water to make the streams more visible.
  * Change the liquid (e.g., salt water vs. fresh water) and discuss density effects.
  * Insert a pressure sensor or force probe at different depths to measure pressure directly.



====Safety Precautions====
  * Use child-safe scissors and only under adult supervision.
  * Conduct outdoors or over a sink to avoid slipping hazards.
  * Ensure bottle edges around the holes are smooth to prevent cuts.
  * Handle carefully when removing tape to avoid splashing.




====Questions to Consider====
  * Why does the bottom hole produce the strongest stream? (Because pressure increases with depth in a fluid.)
  * What would happen if you made a hole right at the waterline? (Water would not flow out strongly because pressure difference is minimal.)
  * How does this principle explain why divers feel pressure on their ears as they descend? (Greater water depth increases the pressure exerted on the body.)
  * How is this principle important for designing submarines or underwater equipment? (They must withstand increasing pressure as depth increases.)