What you have here is a siphon. Gravity (and many theories say atmospheric pressure to some degree- but largely modern experiments show gravity for most liquids) will pull the liquid down. Once the flow of liquid starts in this way, to stop it you must raise the exit higher than the reservoir- which is impractical with a cup as the reservoir is open and the exit drain is the base.
The same principal has been used for wells and irrigation for centuries and then some, and in modern times is often used to remove (or steal) gasoline from vehicle fuel tanks. Before metering pumps (or where they aren’t available or electricity isn’t) IV drips also make use of this principal- which is part of why they were traditionally hung so high up- to make it impractical to get the part of the patient with the tube in them higher than the reservoir (IV bag).
It’s pretty neat and does seem almost nonsensical. But the siphon mechanism is even at work in most toilets, you can usually see an “S” or “U” shaped outline when looking at the toilet, and if you look in the tank you can see the mechanism and the flapper or valve used to stop the flow of water. Fun stuff.
Never met an American huh? My pleasure to introduce you. Would you like to first meet the
“Tips back head and places mouth under hole” variety, or the “let it spill all over me, as long as I drink faster than it drops and you pour faster than I drink it’s fine” variety? I’m leaving out several varieties including the “places Tupperware in purse and steals all your booze by letting it drain into said Tupperware for later enjoyment” variety.
“Tips back head and places mouth under hole” variety, or the “let it spill all over me, as long as I drink faster than it drops and you pour faster than I drink it’s fine” variety? I’m leaving out several varieties including the “places Tupperware in purse and steals all your booze by letting it drain into said Tupperware for later enjoyment” variety.