FOR A liquid drop of radius r falling in air with terminal velocity, power delivered by gravitational force is propotional to

P = m g v

Explanation:

Power is defined as the relationship between work and time

        P = W / t

The work is defined by the scalar product of the force and the displacement, in the case of a drop falling the vertical force and the displacement has the same direction, therefore the angle between them is zero and the cosines of zero is one (cos 0 = 1)

       W = F y

the gravitational force is proportional to the weight of the drop  (F = mg)

        W = mg y

we substitute

       P = m g y / t

the terminal velocity of the drop is constant

       P = m g v

to treat tumors in the body

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .