Question

Statement-I: Fluid exerts pressure on the surface of a solid in contact with it. Statement-II: The excess potential energy of molecules at the surface of a liquid leads to surface tension. Which of the following is correct?

• A. Both are true and statement-II is the correct explanation of statement-I
• B. Both are true but statement-II is not correct explanation of statement-I
• C. Statement-I is true but Statement-II is false
• D. Statement-II is true but statement-I is false

Hint:

In fluid mechanics, remember that while pressure and surface tension are related to the behavior of fluids, their underlying causes can be different.

Answer 1

The Correct Option is B

The question presents two statements related to fluid mechanics and surface tension. We need to verify the correctness of these statements and whether Statement-II explains Statement-I.

1. Examine Statement-I: "Fluid exerts pressure on the surface of a solid in contact with it." This is a true statement. It is a fundamental concept in fluid mechanics that a fluid exerts normal force per unit area (pressure) on any surface with which it is in contact. The pressure is exerted equally in all directions on a surface in contact with a fluid.
2. Examine Statement-II: "The excess potential energy of molecules at the surface of a liquid leads to surface tension." This statement is also true. Surface tension arises because the molecules at the surface of a liquid experience a net inward force due to cohesive forces, leading to excess potential energy. This energy acts to minimize the surface area, manifesting as surface tension.

Both statements are individually true. However, Statement-II, which is about surface tension, does not provide a direct explanation for Statement-I, which addresses the pressure exerted by a fluid on a solid surface. The phenomenon of fluid pressure and surface tension are related in the broader field of fluid dynamics but do not serve as explanations for each other in this specific context.

Conclusion: The correct option is "Both are true but statement-II is not the correct explanation of statement-I."