Question

You are studying for an exam on the eight floors of your luxurious apartment building. You look out from the window and notice that one of your neighbours is giving a party on the ground floor terrace and has placed a huge punch bowl full of an interesting looking beverage (specific gravity $1$) directly below your window. You quickly string together $80$ drinking straws to form a giant straw that can reach the punch bowl $80$ feet below. You dip the straw into the punch and begin to suck. When you use a single drinking straw to drink something, it takes you $0.1\,\sec $ to raise the liquid to your lips. But when you use this giant drinking straw:
(A) you find that you can’t raise the liquid to your lips no matter how hard you try
(B) it takes you $8\,\sec $( $80$ times $0.1\,\sec $ ) to raise the liquid to your lips
(C) it takes you $800\,\sec $ ( $80$ divided by $0.1\,\sec $ ) to raise the liquid to your lips
(D) it takes you $640\,\sec $ ( $80$ times $80$ times $0.1\,\sec $ ) to raise the liquid to your lips

Answer 1

Hint When the liquid or any fluid if we want to make the fluid to go some height, then the pressure in the required point must be less than the pressure of the fluid is initially presented. By using the specific gravity given in the question, the pressure of the fluid at the initial position is determined, then the solution can be determined.

Complete step by step solution
Given that,
You are studying for an exam on the eight floors of your luxurious apartment building. You look out from the window and notice that one of your neighbours is giving a party on the ground floor terrace and has placed a huge punch bowl full of an interesting looking beverage (specific gravity $1$) directly below your window. You quickly string together $80$ drinking straws to form a giant straw that can reach the punch bowl $80$ feet below. You dip the straw into the punch and begin to suck.
From the specific gravity is given in the question,
$SG = \dfrac{\rho }{{{\rho _{water}}}}$
Where, $SG$ is the specific gravity, $\rho $ is the density of the liquid and ${\rho _{water}}$ is the density of the water.
By substituting the specific gravity and density of the water in the above equation, then
$1 = \dfrac{\rho }{{1000}}$
From the above equation, then the density of the beverage is $1000\,kg{m^{ - 3}}$.
The fluid will go above when the pressure in the eight floor is less than the atmospheric pressure. The atmosphere pressure is ${10^5}\,bar$
The pressure of the fluid is $\rho gh$
By substituting the density, acceleration due to gravity and height, then
The pressure of the fluid is $1000 \times 10 \times 80$
On multiplying the terms, then
The pressure of the fluid is \[8 \times {10^5}\,bar\]
The pressure is greater than the atmospheric pressure, so the fluid will not reach

Hence, the option (A) is the correct answer.

Note Due to the pressure difference in the eight floor and the atmospheric pressure in the ground floor, the pressure in the eight floor is maximum, so the fluid will not reach the lips of the man on the eighth floor. The fluid always flows from high pressure to low pressure. So, the fluid will not move up because the low pressure is in the ground floor.