eli5 why can a straw carry water without the bottom dripping but not a pool?

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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

10 Answers

Anonymous 0 Comments

Because of “surface tension.”

In order for water to fall, something needs to replace it or else you get a vacuum. With large amounts of water like a pool, there’s enough area for the surface tension to break and let the air and water swap places. 

However, when you decrease the surface area of the water enough, such as in a thin straw, the water _wants_ to fall out, but can’t due to the fact that the surface tension won’t let air in to replace it.

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