My son just asked me at dinner and I do not have an exact answer.
In: 7
Three things. Capillary forces, vacuum, and surface tension.
Capillary forces are the interaction between the water and the straw. The water is “holding onto” the sides of the straw.
Vacuum is created by gravity pulling down on the liquid in the straw when it is sealed at the other end with your finger.
Surface tension is the water holding onto itself in the bottom of the straw. It is the same thing that makes a drop of water sit in a half sphere when spilled on the counter.
If any of these things break down the water will not stay in the straw.
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