When you block one end of a straw why does the liquid stay in place/in the straw?
In: Physics
The air around the straw has pressure which pushes on everything. When you put your finger over the top of the straw it prevents air from getting in there and pushing on the top of the column of water. When you lift the straw out of the water it is submerged in the water in the straw begins to lower which increases the space between your finger and the top of the water. This increase in space causes the pressure at the top of the straw to drop. The pressure at the bottom of the straw is maintained by the atmosphere which pushes up on the water holding it in the straw. The amount the pressure drops at the top of the straw is equal to the water pressure at the bottom of the cup you pulled it out of.
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