Correct option: (C) 0.1 (m/s)
Explanation:
Terminal speed = V = (2/g) [{r2g(ρ – σ)} / η] ----- by stoke’s law
Where η = viscosity
ρ = density of solid
σ = density of liquid
∴ size is same ⇒ r is constant
η is also constant
Hence
V ∝ (ρ – σ)
ρ1 = 19.5
ρ2 = 10.5
σ = 1.5
V1 = 0.2 m/s
Hence
(V2 / V1) = [{ρ2 – σ} / {ρ1 – σ}]
= [{10.5 – 1.5} / {19.5 – 1.5}]
V2 = (9 /18) × V1
= (V1 / 2)
= (0.2 / 2)
= 0.1 m/s