How Everything Works
How Everything Works How Everything Works

Question 1375

How do the automatic soda dispensers at fast food joints know when the cup is full? — MB, San Diego, CA
Those dispensers measure the volume of liquid they dispense and shut off when they've delivered enough liquid to fill the cup. They don't monitor where that liquid is going, so if you put the wrong sized cup below them or press the button twice, you're in trouble.

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