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#air pressure

2 public questions tagged with this topic.

Surface Tension, Capillarity and Excess Pressure

Why does blowing over a piece of paper lift it upwards?

Bernoulli’s principle states that faster airflow above the paper reduces pressure, while slower air below maintains higher pressure, creating an upward lift due to the pressure difference. As per NCERT, applying relevant law/formula with correct units and sign convention leads to Due to lower pressure above from faster airflow. 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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Viscosity, Stokes' Law and Reynolds Number

What is the total pressure at a depth of 1.6m in air (ρ\=1.29kg/m3) with atmospheric pressure 1.01×105Pa? (Take g\=9.8m/

Total pressure: P = Pa+ρgh. Pa = 1.01×105Pa, ρ = 1.29kg/m3, g = 9.8m/s2, h = 1.6m. P = 1.01×105+1.29×9.8×1.6 = 1.01×105+20.23 = 1.0102023×105Pa. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 1.01 × 10⁵ Pa. This satisfies dimensional consistency and physical conditions given, so option A is scientifically correct.

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

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