Eight small drops of equal size are falling through air with a steady velocity of 10 cm/sec. If the drops coalesce, what would be the terminal velocity of the bigger drop?
The correct option is A 40 cm/s
Terminal velocity , vT=2r2(σ−ρ)g9η
where σ→ density of body falling through the given fluid of density ρ
Let the terminal velocity for smaller drop (r) and bigger drop (R) be vT and v′T respectively.
After the small drops coalesce, Volume of the big drop=8×Volume of each small drop
Given, terminal velocity (steady velocity) of small drop is vT=10 cm/s
Substituting in Eq.(i),
Terminal velocity of bigger drop will be