Essentially my question is this: if I get a straw and put it in water, I cover my thumb on the top and pull out, water doesn’t want to leave. Idk why or how but regardless.
How come this same thing doesn’t apply for a swimming pool? Like a body of water is suspended because it has a lid or roof?
In: Physics
Surface tension. When you cover the top of a straw the reason it doesn’t fall out is that there is a vacuum at the top of the straw between your finger and the water. The atmospheric pressure of the air surrounding the straw pushes the water up into the straw with an amount of force that balances the weight of the water. The straw is small enough that the surface tension of the water prevents the air from getting up into the straw through the water (which would get rid of the vacuum).
If you were to take a full pool and flip it upside down and lift it into the air all the water would fall out because the pool area is very large and surface tension is not a strong enough force to prevent air from traveling up the water. With no vacuum there is no way to keep all that water there.
This video has horrible music but illustrates the effect: [https://www.youtube.com/watch?v=65T4ReLkjCg&ab_channel=MocomiKids](https://www.youtube.com/watch?v=65T4ReLkjCg&ab_channel=MocomiKids)
They put a piece of paper to prevent air flow and the water doesn’t fall. If you could do that with a pool it would work. With a straw the surface tension is enough that you don’t need paper to prevent air flow.
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