Given below are two statements :
Statement I : Pressure of a fluid is exerted only on a solid surface in contact as the fluid-pressure does not exist everywhere in a still fluid.
Statement II : Excess potential energy of the molecules on the surface of a liquid, when compared to interior, results in surface tension.
In the light of the above statements, choose the correct answer from the options given below

Solution

Physics sir · 3 steps

Pressure lives at every point inside a still fluid, not just at the walls; that is what kills Statement I.

1. Statement I. Pressure exists at every point inside a fluid at rest, and at a depth h it equals P₀ + ρ g h. Any surface you imagine inside the fluid feels this push from both sides, so pressure is not limited to solid surfaces in contact. Statement I is false.

   P = P₀ + ρ g h

2. Statement II. A molecule deep inside the liquid is pulled equally from all sides. A molecule at the surface has neighbours only below and beside it, so it has extra potential energy compared with one inside. The liquid shrinks its surface to lower this extra energy, and that is surface tension. Statement II is true.
3. So. Statement I is false and Statement II is true, which is option (a).

The idea to keep. Pressure in a still fluid is a property of every point in it, given by P₀ + ρ g h. Surface tension comes from surface molecules having extra energy because they have fewer neighbours.

Answer from the NTA final answer key. Solution by PrepWiser.