Question

Bantu slips into a large lake and he doesn't know swimming. But he is a great fan of Superman. He shouted for help remembering Superman. As usual, Superman arrives on the top of a cliff and, due to some reason, Superman lost his flying power immediately after arrival on cliff. Due to shortage of time, somehow, Superman manages a strong and long straw and decided to drink whole water of lake to save Bantu.(Data:Atmospheric pressure $=1.2\times {10}^{5}Pa,g=10m/s^2$, density of water$=1000kg/m^3)$ Assume Superman has infinite power and ability to drink whole water. Which of the following statements is/are true?
(1) Superman cannot save Bantu by this way.
(2) Superman can drink some water but not whole water.
(3) Superman will save Bantu by drinking whole water.

• A. Only (1) & (2)
• B. Only (3)
• C. Only (1)
• D. All (1), (2) & (3) are wrong

Answer 1

Answer: (C)

Only (1)

The water can rise in the straw only upto a level which would make the pressure at the bottom of the straw equal to the atmospheric pressure. Thus the maximum height of the liquid in the straw is given as $\rho gh=1000\times 10\times h=P_{atm}=1.2\times {10}^5$
or
h=12 m.
As the straw is more than 12.5 m, Superman cannot save Bantu.