10-d1 Adrinking straw works because, when you suck air out of the straw, there i

Question

10-d1 Adrinking straw works because, when you suck air out of the straw, there is decreased pressure. The equilibrium water level inside the straw is such that the pressure at the water level outside the straw (atmospheric pressure) is equal to the pressure at the same height inside the straw. Inside the straw, there are two contributions: the air pressure inside the straw plus the column of water above this height.

(a) Suppose you find that you can only suck water up to a height of 1.0 m. What is the minimum pressure inside the straw?

(b) Superman, strong as he is, can suck out all the air from a (strong-walled) straw. What is the tallest straw through which Superman can drink water out of a lake?

Explanation / Answer

a) let ap be the pressure inside the straw, and the atmospheric pressure is Pa

P+ gh= Pa

P=101325 - 1000*9.8*1

P= 91525 pascal

b) gh= Pa

1000*9.8*h = 101325

h= 10.339 metres

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