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#drag force

4 public questions tagged with this topic.

Equation of Continuity and Flow Rate

Which of the following statements is correct about terminal velocity?

Terminal velocity occurs when the viscous force (proportional to velocity) equals the net gravitational force, resulting in zero acceleration and constant speed, as per Stokes’ law. As per NCERT, applying relevant law/formula with correct units and sign convention leads to It occurs when forces balance. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

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Fluid Pressure, Pascal's Law and Manometers

A sphere of radius 0.03m falls through machine oil (η\=0.113Pa s) at 0.15m/s. What is the viscous drag force?

Stokes’ law: F = 6πηav. η = 0.113Pa s, a = 0.03m, v = 0.15m/s. F = 6×3.14×0.113×0.03×0.15 = 0.0958N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 0.096 N. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

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Surface Tension, Capillarity and Excess Pressure

A plate of area 0.09m2 moves at 0.5m/s over a 1.0mm thick water film (η\=1.0×10−3Pa s). What force is required?

Viscous force: F = ηvAl. η = 1.0×10−3Pa s, v = 0.5m/s, A = 0.09m2, l = 1.0×10−3m. F = 1.0×10−3×0.5×0.091.0×10−3 = 1.0×10−3×45 = 0.045N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 0.045 N. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.

Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.

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