Two houses have identical pipes and identical taps on the ground floor
Two houses have identical pipes and identical taps on the ground floor. One house has a tall, narrow water tank on its roof; the other has a short, wide tank that holds far more water, but its water surface sits lower than the tall tank's. Neelam says water will gush out harder from the tap fed by the tall, narrow tank. Aakash says it will be the wide tank's tap, because that tank holds more water, and more water means more pressure. Whose prediction is correct?
Who do you think is right? Pick one.
The answer: Neelam is right, pressure depends on the height of the water column, not the amount
Why
Aakash's idea feels obvious — more water ought to push harder — and the wide tank really does hold more. But the pressure at a point in a liquid depends on how tall the column of liquid above that point is, not on how much liquid there is in total. The extra water in the wide tank is spread out sideways; it is not stacked any higher above the tap. The tall tank's water surface sits higher above the tap, so the column of water pressing down at that tap is taller, and the pressure there is greater. The wide tank would keep its tap running for longer before emptying, but not harder. That is why water tanks go on the highest roof, and why a town's overhead tank stands on a tall tower. Test: fill a narrow bottle and a wide bucket to the same water height and make an identical small hole near the bottom of each — the two jets reach about the same distance, even though the bucket holds far more water. Neelam is right: the tap fed by the taller column of water gets more pressure, because liquid pressure depends on height, not on the amount of water.
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