Consider a spherical ash particle of diameter 65 m, falling from a volcano at a high elevation

Consider a spherical ash particle of diameter 65 μm, falling from a volcano at a high elevation in air whose temperature is –50°C and whose pressure is 55 kPa. The density of air is 0.8588 kg/m³ and its viscosity is 1.474 × 10^–5 kg/m·s. The density of the particle is 1240 kg/m³. The drag force on a sphere in creeping flow is given by F_D = 3πμVD. The terminal velocity of this particle at this altitude is

(a) 0.096 m/s 

(b) 0.123 m/s 

(c) 0.194 m/s

(d) 0.225 m/s 

(e) 0.276 m/s