#viscous drag

Viscosity, Stokes' Law and Reynolds Number

A sphere of radius 0.025m moves at 0.08m/s through blood (η\=2.7×10−3Pa s). What is the viscous drag force?

Stokes’ law: F = 6πηav. η = 2.7×10−3Pa s, a = 0.025m, v = 0.08m/s. F = 6×3.14×2.7×10−3×0.025×0.08 = 1.017×10−4N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 1.0 × 10⁻⁴ 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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Equation of Continuity and Flow Rate

A sphere of radius 0.04m moves at 0.12m/s through honey (η\=0.2Pa s). What is the viscous drag force?

Stokes’ law: F = 6πηav. η = 0.2Pa s, a = 0.04m, v = 0.12m/s. F = 6×3.14×0.2×0.04×0.12 = 0.1809N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 0.18 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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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 sphere of radius 0.035m moves at 0.09m/s through glycerine (η\=0.83Pa s). What is the viscous drag force?

Stokes’ law: F = 6πηav. η = 0.83Pa s, a = 0.035m, v = 0.09m/s. F = 6×3.14×0.83×0.035×0.09 = 0.0493N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 0.05 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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Surface Tension, Capillarity and Excess Pressure

A sphere of radius 0.045m moves at 0.15m/s through machine oil (η\=0.034Pa s). What is the viscous drag force?

Stokes’ law: F = 6πηav. η = 0.034Pa s, a = 0.045m, v = 0.15m/s. F = 6×3.14×0.034×0.045×0.15 = 0.0433N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 0.043 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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Equation of Continuity and Flow Rate

A sphere of radius 0.05m moves at 0.11m/s through blood (η\=2.7×10−3Pa s). What is the viscous drag force?

Stokes’ law: F = 6πηav. η = 2.7×10−3Pa s, a = 0.05m, v = 0.11m/s. F = 6×3.14×2.7×10−3×0.05×0.11 = 0.0028N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 0.0028 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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Fluid Pressure, Pascal's Law and Manometers

A sphere of radius 0.07m moves at 0.14m/s through honey (η\=0.2Pa s). What is the viscous drag force?

Stokes’ law: F = 6πηav. η = 0.2Pa s, a = 0.07m, v = 0.14m/s. F = 6×3.14×0.2×0.07×0.14 = 0.0369N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 0.036 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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