Question

Determine the radius of a drop of rain falling through air with terminal velocity 0.12 ms^–1. Given η = 1.8 × 10^–5 kg m^–1 s^–1, ρ = 1.21 kg m^–3, σ = 1.0 × 10³ kg m^–3 and g = 9.8 m s^–2.

Answer 1

 We know that terminal velocity is given by

On rearranging terms, we can write