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#fluid statics

3 public questions tagged with this topic.

PHYSICS

A submarine window ( 0.03 m² ) is at 500 m depth in seawater ( rho = 1.03 × 10³ kg/m³ ). What force acts on it if in

Given: A submarine window ( 0.03 m² ) is at 500 m depth in seawater ( rho = 1.03 × 10³ kg/m³ ). What force acts on it if inside pressure is atmospheric? (Take g = 10 m/s² ) These values define the system as per NCERT data. Formula: Gauge pressure: P_g = rho g h = 1.03 × 10³ × 10 × 500 = 5.15 × 10⁶ Pa. This is the standard NCERT relation for this phenomenon. Substitution & Calculation: F = P_g A = 5.15 × 10⁶ × 0.03 = 1.545 × 10⁵ N . Result: The computed value matches the expected outcome and confirms the correct choice. Units and powers like J kg⁻¹ K⁻¹, m

Ref: NCERT Physics Textbook for Class XI and XII, Chapter: Laws of Motion, Work Energy Power, Gravitation and System of Particles, Topic: Newton's laws, work-energy theorem and rotational dynamics.

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Surface Tension, Capillarity and Excess Pressure

Why do fluids exert pressure only normal to a surface at rest?

In a fluid at rest, any tangential (shear) force would cause the fluid to flow due to its inability to resist shear stress. According to Newton’s third law, if a tangential force existed, the fluid would exert an equal and opposite force, leading to motion. Since the fluid is at rest, no such motion occurs, and the force must be normal to the surface.

Ref: NCBI Bookshelf, Ideal Gas Law: P1V1/T1 = P2V2/T2.

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