Surface Environment, Mine Ventilation and Underground Hazards · Surface Environment · 2 marks · Numerical answer
A2.5 μm dust particle of density3600 kg/m³ settles500 m through still air of viscosity1.80×10⁻⁵ kg/(m s). Neglect air density and turbulence. Find settling time in days to two decimals.
Use Stokes settling speed v=ρgd²/(18μ). Substituting SI units gives v≈0.00068125 m/s. Time=500/v≈733945 s; divide by86400 s/day to obtain8.49 days. The diameter must be converted from micrometres to metres before squaring.
More Surface Environment questions
GATE 2026 MN Q54– A15 mL wastewater sample is diluted to300 mL and incubated for5 days at20°C. Dissolved…
GATE 2025 MN Q21– The environmental lapse-rate profiles are shown. Dry adiabatic lapse rate is−10°C/km.…
GATE 2025 MN Q57– Noise is80 dB(A) for10 min and60 dB(A) for30 min. Find the40-min energy-equivalent level…
GATE 2025 MN Q62– A10×10 km airshed emits20 kg SO₂/s. Wind speed is4 m/s and mixing height1200 m. Incoming…
GATE 2025 MN Q64– Ultimate BOD is300 mg/L. The20°C rate constant is0.22/day and temperature coefficient1.05.…
GATE 2024 MN Q29– A washery discharges 300 m³/day of water at DO 4 mg/L into a stream flowing 0.04 m³/s at…