40+ Everyday Things That Make Perfect Sense When We Understand The Idea Behind
The hole in the top of a coffee cup may serve two purposes. Both of them are based on simple physical laws. If there is only one hole in a container of liquid, the liquid cannot be poured from it smoothly. In this case, the air will enter the cup through the same hole the coffee is flowing.
This means without the additional hole your drink would bubble and splash - the last thing you want from a hot coffee you are trying to enjoy. Also, the top acts as an insulator for the heat of the drink. The hole allows the hot steam to escape so that we do not get burned when we try to drink our coffee in the morning and reduce the pressure to avoid other accidents.
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