When you block one end of a straw why does the liquid stay in place/in the straw?
In: Physics
So air has ‘weight’ technically, so our gravity exerts a force on our atmosphere so it doesnt go flying off into space. Now this force is like a bottle of water, if u make a hole in it while the top is open, it flows out because the water actually was exerting force, actually pressure on the walls of the container. So making a hole lets it relieve some of that pressure energy and thus water flows off. Now if water doesn’t flow out, then the force of gravity acting on the water which is relieved through that hole needs to be cancelled out with an equal and opposing force. When the bottle is open and u make a hole, the force by the atmosphere acting in the top of the liquid via the cap hole is more or less equal to what it applied on the hole u made, so those forces dont matter. But when u close the cap, u dont let the atmospheric force from the top push ur water, so as water goes out and the force lessens on the hole, it reaches a point where the atmospheric force can counteract the waters force going outside. So in a closed cap bottle with a hole at the bottom, all the water wouldnt go out if u don’t let air get inside. Now imagine that the hole is huge and at the very bottom of the bottle completely and that the bottle is small and cylindrical and the top of the bottle isnt closed by the plastic but rather by ur hand. Now u have a miniature straw. Same concept
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