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
Water has surface tension. Trying to think of a good way to explain it, it’s almost like the water develops a “skin” that’s trying to hold itself together. It’s why water forms drops on a surface instead of just spreading out thinly, and why things can rest on the surface of water (pond skater insects etc.)
The hole in the bottom of a straw is small enough that surface tension can hold it together. But as the opening gets bigger surface tension isn’t enough and it breaks and the water falls out. That’s why you can’t do the same trick with a cup.
Also you need to hold the end as if the straw is open the cylinder of water can just slide out as a single piece. When you hold the end you create a vacuum that holds the top of the cylinder of water in place.
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