Statement-1: The free surface of a liquid at rest relative to a stationary container is always normal to the effective gravitational field. Statement-2: A liquid at rest cannot sustain shear stress.
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Statement-1: The free surface of a liquid at rest relative to a stationary container is always normal to the effective gravitational field. Statement-2: A liquid at rest cannot sustain shear stress.

G1 Physics · Accepted Answer

Step 1: A liquid at rest cannot sustain shear stress; therefore the resultant pressure force on its free surface must be normal to that surface. Step 2: Hydrostatic equilibrium requires the pressure gradient to be parallel to effective gravity, so the free surface (constant pressure) is perpendicular to effective gravity. Thus both statements are true and Statement-2 explains Statement-1. Correct answer: A.