1. No Air Inside: By filling the bottle completely and sealing it, you remove all the air. This means there is no air pressure inside the bottle pushing down on the water.

2. Atmospheric Pressure: The air outside the bottle is constantly pushing on every surface with a significant force (about 14.7 pounds per square inch at sea level). This pressure pushes up on what is now the bottom of the upside-down bottle.

3. The Pressure Imbalance: The situation looks like this:

   • Force trying to push water out: Gravity (pulling down on the mass of the water).

   • Force keeping water in: Atmospheric pressure (pushing up on the bottle's base).
     Since there's no counter-pressure from inside, the external atmospheric pressure wins, holding the water in place.

4. The Role of the Plastic Bottle: Plastic is flexible. Unlike a rigid glass bottle, the plastic will often deform. As the water tries to move down slightly, it creates a tiny partial vacuum inside. The stronger outside air pressure then squeezes or "crushes" the bottle slightly inward until the pressures are balanced. This is a visible proof that a pressure imbalance exists.

Yuyao BILL Sprayer Co.,Ltd is a professional manufacturer specialized in the production of various kinds of mini trigger sprayer, prefume sprayer, pet bottles and any other comestic packaging products. Now we have a complete set of technology and equipment, including full automatic injection machines and full automatic assembling equipment line, to ensure the production to reach 4000000 ,even more each month. Then the professional spectors to check each process during the whole production to ensure the quality of every product have no any problem, some process with professional testing machines.

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