Questions on fluid viscosity, drag forces in viscous flow, Stokes' law for small particles, and Reynolds number for flow regime classification. Tests knowledge of fluid resistance and flow types.
Pressure transmitted: P = F1A1 = F2A2. F2 = F1×A2A1. F1 = 50N, A1 = 0.02m2, A2 = 0.1m2. F2 = 50×0.10.02 = 50×5 = 250N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 250 N. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.
Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.
Gauge pressure: Pg = ρgh = 1.03×103×10×600 = 6.18×106Pa. F = PgA = 6.18×106×0.05 = 3.09×105N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 3.09 × 10⁵ N. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.
Ref: NCBI Bookshelf, Ideal Gas Law: P1V1/T1 = P2V2/T2.
Torricelli’s law (v = 2gh) shows that the efflux speed depends only on depth, remaining constant near the hole until external factors (e.g., air resistance or gravity’s vertical effect) alter its trajectory.
Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.
In streamline flow, fluid particles follow fixed paths (streamlines) with constant velocity at each point, occurring at low speeds where viscous forces dominate, not requiring high speed or turbulence. As per NCERT, applying relevant law/formula with correct units and sign convention leads to Particles follow fixed paths. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.
Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.
Bernoulli’s equation: P1+12ρv12+ρgh1 = P2+12ρv22+ρgh2. P1 = 1.2×105, v1 = 2m/s, h1 = 1m, v2 = 4m/s, h2 = 0m. Left: 1.2×105+12×1000×4+1000×10×1 = 1.2×105+2000+10000 = 1.32×105. Right: P2+12×1000×16 = P2+8000. 1.32×105 = P2+8000, P2 = 1.24×105Pa.
Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.
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.
Torricelli’s law: v = 2gh. g = 10m/s2, h = 0.9m. v = 2×10×0.9 = 18≈4.24m/s. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 4.2 m/s. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.
Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.
ΔP⋅A = mg. mg = 4.5×105×9.8 = 4.41×106N, A = 600m2. ΔP = 4.41×106600 = 7350Pa. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 7350 Pa. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.
Ref: NCBI Bookshelf, Ideal Gas Law: P1V1/T1 = P2V2/T2.
The barometer measures atmospheric pressure (Pa = ρgh). During a storm, atmospheric pressure drops, reducing the force supporting the mercury column, causing its height to decrease, as noted in the chapter.
Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.
Capillary rise (h = 2Scosθ/ρgr) is inversely proportional to radius, not directly proportional. The incorrect statement is that height increases with tube radius. As per NCERT, applying relevant law/formula with correct units and sign convention leads to Height increases with radius. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.
Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.
Gauge pressure: Pg = ρgh = 1.03×103×9.8×200 = 2.0194×106Pa. F = PgA = 2.0194×106×0.09 = 1.81746×105N. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 1.82 × 10⁵ N. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.
Ref: NCBI Bookshelf, Ideal Gas Law: P1V1/T1 = P2V2/T2.
Capillary rise: h = 2Scosθρga. S = 0.4355N/m, ρ = 13.6×103kg/m3, g = 10m/s2, a = 0.2×10−3m, cosθ = −0.5. h = 2×0.4355×(−0.5)13.6×103×10×0.2×10−3 = −0.016m = −1.6cm. As per NCERT, applying relevant law/formula with correct units and sign convention leads to -1.6 cm. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.
Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.
