Two drops of the same radius are falling through air with a steady velocity of 5 cm per sec. If the two drops coalesce, the terminal velocity would be

If two drops of same radius r coalesce then radius of new drop is given by R43πR3=43πr3+43πr3⇒R3=2r3⇒R=21/3rIf drop of radius r is falling in viscous medium then it acquire a critical velocity v and  v∝r2v2v1=Rr2=21/3rr2⇒v2=22/3×v1=22/3×(5)=5×(4)1/3 cm/s