Fluid Mechanics

JEE Main level, single correct, medium

29 of 192

Question 29 of 192

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: When you squeeze one end of a tube to get toothpaste out from the other end, Pascal’s principle is observed.

Reason R: A change in the pressure applied to an enclosed incompressible fluid is transmitted undiminished to every portion of the fluid and to the walls of its container.

In the light of the above statements, choose the most appropriate answer from the options given below.

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Answer: (D) Both A and R is correct and R is the correct explanation of A

Pascal's law states that the pressure in a closed incompressible fluid is transmitted equally in all directions.
The formula for pressure is given by

P=FAP=\dfrac{F}{A}
When a toothpaste is squeezed let the pressure transmitted by
PP. At the mouth of the toothpaste the pressure will also be equal to PP due to Pascal's law. The pressure applied to the tube is transmitted equally throughout the toothpaste. When the pressure reaches the open end, it forces toothpaste out through the opening. Hence, both A&R is correct and RR is correct explanation for AA.

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